Bulk acoustic wave filter and method of making the same

Abstract

The application provides a bulk acoustic wave filter and a preparation method thereof. By arranging a support column in a cavity to support a lower electrode and a film layer above the lower electrode, the end of the lower electrode can be arranged in a region of the cavity in a suspended manner without being supported by the side wall of the cavity, and the lower electrode extension and the upper electrode extension can be staggered outside the cavity in a more flexible manner. Furthermore, on the basis of realizing electrical leads of the upper and lower electrodes, the upper and lower electrodes can be effectively avoided from overlapping outside the cavity, mechanical energy loss caused by the overlapping of the upper and lower electrodes in a non-effective resonance region is reduced, and the Q value of the device is improved.

Description

Technical Field

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

[0002] Resonant structures made using the inverse piezoelectric effect of piezoelectric materials are key components of crystal oscillators and filters, and are frequently used in bulk acoustic wave (BAW) filters. BAW filters are mainly constructed using two methods: air-gap type and solid-mount (SMR) type. Air-gap type filters typically employ MEMS manufacturing processes to create an air gap within the substrate to confine sound waves within the piezoelectric resonator. This structure exhibits a high Q value and good mechanical strength.

[0003] For details, please refer to [link / reference]. Figure 1 A schematic diagram of a bulk acoustic wave (BAW) filter is shown. The BAW filter includes resonant structures stacked sequentially on a substrate, with the resonant structures located at least above a cavity 11 within the substrate. Specifically, the resonant structure includes a lower electrode 21, a piezoelectric material layer 22, and an upper electrode 23 stacked sequentially. The overlapping region of the lower electrode 21, the piezoelectric material layer 22, and the upper electrode 23 directly above the cavity 11 constitutes the effective resonant region 20a of the resonant structure. The edge of the lower electrode 21 typically needs to extend laterally out of the cavity 11 so that the edge of the lower electrode 21 can be mounted on the edge of the cavity 11, thereby supporting the lower electrode 21 and its overlying film layer. Similarly, the upper electrode 23 also needs to extend laterally out of the cavity 11 to achieve electrical lead-out of the upper electrode 23.

[0004] However, the portion of the upper electrode 23 extending laterally out of the cavity inevitably overlaps spatially with the portion of the lower electrode 21 mounted on the edge of the cavity. That is, the upper electrode 23 and the lower electrode 21 also overlap spatially outside the cavity 11, forming an external overlap region 20b. This external overlap region 20b, as an ineffective resonant region of the resonant structure, generates lateral modal mechanical vibrations at the edge of the effective resonant region 20a, causing additional mechanical losses and generating some noise, thereby reducing the Q value of the resonant structure. Summary of the Invention

[0005] The purpose of this invention is to provide a bulk acoustic wave filter to reduce the mechanical losses generated in the ineffective resonant region of the bulk acoustic wave filter and improve the Q value of the device.

[0006] To address the aforementioned technical problems, the present invention provides a bulk acoustic wave filter, comprising: a substrate in which a cavity is formed; a resonant structure including a lower electrode, a piezoelectric material layer, and an upper electrode sequentially disposed on the substrate, the upper electrode having an upper electrode extension extending out of the cavity, the lower electrode having a lower electrode extension extending out of the cavity, the lower electrode extension and the upper electrode extension being offset from each other outside the cavity; and the end of the lower electrode not extending out of the cavity being suspended above the cavity; and a support column disposed within the cavity and located below the suspended end of the lower electrode for supporting the lower electrode.

[0007] Optionally, the lower electrode includes a lower electrode body and a lower electrode lead-out end that connects to the side of the lower electrode body and extends out of the cavity; the upper electrode includes an upper electrode body and an upper electrode lead-out end that connects to the side of the upper electrode body and extends out of the cavity. The upper electrode extension includes the upper electrode lead-out end, and the lower electrode extension includes the lower electrode lead-out end.

[0008] Optionally, the upper electrode extension includes only the upper electrode lead-out end, and the lower electrode extension includes the lower electrode lead-out end and the portion of the lower electrode body extending out of the cavity.

[0009] Optionally, both the lower electrode body and the upper electrode body are positioned directly above the cavity.

[0010] Optionally, the lower electrode body has a polygonal structure, and the support column is located below the apex corner of the polygonal structure.

[0011] Optionally, the support column is disposed outside the projection area of ​​the upper electrode body.

[0012] Optionally, a support portion protruding toward the outer periphery of the cavity is provided on the suspended end of the lower electrode, and the support column is located below the support portion.

[0013] Optionally, the overlapping areas of the lower electrode, the piezoelectric material layer, the upper electrode, and the cavity constitute an effective resonant region, and the support protrudes beyond the effective resonant region.

[0014] Another object of the present invention is to provide a method for fabricating a bulk acoustic wave filter, comprising: providing a substrate in which a cavity is formed and a sacrificial material layer is filled in the cavity; forming a support pillar in the sacrificial material layer; sequentially forming a lower electrode, a piezoelectric material layer and an upper electrode on the substrate, wherein the upper electrode has an upper electrode extension extending out of the cavity, the lower electrode has a lower electrode extension extending out of the cavity, the lower electrode extension and the upper electrode extension are offset from each other outside the cavity, and the end of the lower electrode that does not extend out of the cavity covers the support pillar; and removing the sacrificial material layer.

[0015] Optionally, the method for forming the support post includes: etching the sacrificial material layer to form a through hole, and filling the through hole with a support material to form the support post.

[0016] In the bulk acoustic wave filter provided by this invention, by setting a support column in the cavity to support the lower electrode and the film layer above it, the end of the lower electrode can be suspended in the cavity area without being supported by the side wall of the cavity. It can also more flexibly realize that the extension of the lower electrode and the extension of the upper electrode are staggered outside the cavity. In this way, while realizing the electrical lead-out of the upper and lower electrodes, the overlap of the upper and lower electrodes outside the cavity can be effectively avoided, reducing the mechanical energy loss caused by the overlap of the upper and lower electrodes in the non-effective resonant region and improving the Q value of the device. Attached Figure Description

[0017] Figure 1 This is a top view of an existing bulk acoustic wave filter.

[0018] Figure 2 This is a top view of a first type of bulk acoustic wave filter in one embodiment of the present invention.

[0019] Figure 3 This is a schematic diagram of the lower electrode of the first type of bulk acoustic wave filter in one embodiment of the present invention.

[0020] Figure 4 This is a schematic diagram of the electrodes of the first type of bulk acoustic wave filter in one embodiment of the present invention.

[0021] Figure 5 This is a cross-sectional schematic diagram of a bulk acoustic wave filter in one embodiment of the present invention.

[0022] Figure 6 This is a top view of a second type of bulk acoustic wave filter in one embodiment of the present invention.

[0023] Figure 7 This is a schematic flowchart of the fabrication method of a bulk acoustic wave filter according to an embodiment of the present invention.

[0024] Figures 8-11 This is a schematic diagram of the structure of a bulk acoustic wave filter in the fabrication process of an embodiment of the present invention.

[0025] The accompanying figure is labeled as follows:

[0026] 11-Cavity;

[0027] 21-Lower electrode;

[0028] 22-Piezoelectric material layer;

[0029] 23 - Upper electrode;

[0030] 20a - Effective resonant region;

[0031] 20b - External overlap region of the cavity;

[0032] 100-substrate;

[0033] 110-Cavity;

[0034] 200-resonant structure;

[0035] 210 - Lower electrode;

[0036] 211 - Lower electrode extension;

[0037] 212-Support section;

[0038] 220 - Piezoelectric material layer;

[0039] 230 - Upper electrode;

[0040] 231 - Upper electrode extension;

[0041] 300-Support Column;

[0042] 410 - Lower electrode interconnect;

[0043] 420 - Upper electrode interconnect;

[0044] 500 - Sacrificial material layer. Detailed Implementation

[0045] The core idea of ​​this invention is to provide a bulk acoustic wave filter, which additionally provides a support column for supporting the suspended end of the lower electrode, so that at least part of the edge of the lower electrode can be recessed into the cavity area, avoiding the lower electrode and the upper electrode from overlapping each other outside the cavity, thereby eliminating the transverse modal mechanical vibration caused by the overlap of the upper and lower electrodes outside the effective resonant region, reducing mechanical loss, and improving the Q value of the device.

[0046] The bulk acoustic wave filter and its fabrication method proposed in this invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. The advantages and features of this invention will become clearer from the following description. It should be noted that the drawings are all in a very simplified form and use non-precise proportions, and are only used to facilitate and clarify the illustration of the embodiments of this invention. It should be understood that relative terms such as "above," "below," "top," "bottom," "lateral," "upper," and "lower" shown in the drawings can be used to describe the relationships between various elements. These relative terms are intended to cover different orientations of elements other than those depicted in the drawings. For example, if the device is inverted relative to the view in the drawings, an element described, for example, as being "above" another element will now be below that element.

[0047] in, Figure 2 This is a top view of the first type of bulk acoustic wave filter in one embodiment of the present invention. Figure 3 This is a schematic diagram of the lower electrode of the first type of bulk acoustic wave filter in one embodiment of the present invention. Figure 4 This is a schematic diagram of the upper electrode of the first type of bulk acoustic wave filter according to an embodiment of the present invention. Figure 5 This is a cross-sectional schematic diagram of a bulk acoustic wave filter in one embodiment of the present invention. Figure 6 This is a top view of a second type of bulk acoustic wave filter in one embodiment of the present invention.

[0048] First, combine Figures 2-4 as well as Figure 5 As shown, the semiconductor structure in this embodiment includes a substrate 100 and a resonant structure 200 formed on the substrate 100.

[0049] In this embodiment, a cavity 110 is further formed within the substrate 100, and the resonant structure 200 is formed at least above the cavity 110. In this embodiment, the resonant structure 200 can be used to further constitute a film bulk acoustic resonator (FBAR).

[0050] Continue to refer to Figure 2As shown, the resonant structure 200 includes a lower electrode 210, a piezoelectric material layer 220, and an upper electrode 230 sequentially disposed on the substrate 100. Specifically, the lower electrode 210, the piezoelectric material layer 220, and the upper electrode 230 have overlapping portions above the cavity 110, and the overlapping regions of the lower electrode 210, the piezoelectric material layer 220, the upper electrode 230, and the cavity 110 constitute an effective resonant region. The lower electrode 210 and the upper electrode 230 can be made of the same material, for example, both including molybdenum. The piezoelectric material layer 220 is made of at least one of zinc oxide (ZnO), aluminum nitride (AlN), and lead zirconate titanate (PZT).

[0051] Furthermore, the upper electrode 230 has an upper electrode extension 231 extending out of the cavity 110, and the lower electrode 210 has a lower electrode extension 211 extending out of the cavity 110. The upper electrode extension 231 and the lower electrode extension 211 extend out of the cavity 110 in different regions, so that the lower electrode extension 211 of the lower electrode 210 and the upper electrode extension 231 of the upper electrode 230 are staggered from each other outside the cavity 110. Specifically, the lower electrode 210 and the upper electrode 230 are partially located directly above the cavity 110, within the orthographic projection area of ​​the cavity 110; and the lower electrode 210 also partially extends laterally from directly above the cavity 110 beyond the orthographic projection area of ​​the cavity to form the lower electrode extension 211, and the upper electrode 230 also partially extends laterally from directly above the cavity 110 beyond the orthographic projection area of ​​the cavity to form the upper electrode extension 231.

[0052] It should be noted that "lateral extension" as used here specifically refers to extension along a direction parallel to the substrate surface. Furthermore, "orthographic projection area" as used here refers, for example, the projection area projected onto the substrate surface.

[0053] That is, the lower electrode 210 and the upper electrode 230 only have overlapping areas above the cavity 110, and there are no overlapping areas outside the cavity 110. At this time, the end of the lower electrode 210 that does not extend out of the cavity is suspended above the cavity 110. It can be considered that the upper electrode extension 231 extends out of the cavity 110 above the suspended end of the lower electrode 210, and the end of the upper electrode 230 corresponding to the lower electrode extension 211 is also restricted to directly above the cavity 110 and does not extend out of the cavity 110.

[0054] In a specific example, the upper electrode extension 231 and the lower electrode extension 211 may extend out of the cavity 110 in different directions, for example... Figure 2In the example shown, the lower electrode extension 211 extends in a second direction (Y1 direction), and the upper electrode extension 231 extends in a first direction (X1 direction). Alternatively, the upper electrode extension 231 and the lower electrode extension 211 extend into the cavity 110 at offset positions parallel to the substrate surface. For example, the upper electrode extension 231 and the lower electrode extension 211... Figure 2 The paper shows the staggered arrangement of the pieces.

[0055] In this embodiment, the upper electrode extension 231 and the lower electrode extension 211 extend into the cavity 110 in different directions, as an example. It should be noted that "different directions" here refers to the specific orientation of the electrode extensions, where intersecting directions are considered different directions, for example... Figure 2 In the case of X1 and Y1, which are different directions, directions that are opposite to each other are also considered different directions. For example... Figure 2 In the middle, the X1 direction and the X2 direction are different directions, and the Y1 direction and the Y2 direction are different directions.

[0056] Specifically, the upper electrode extension 231 of the upper electrode 230 extends out of the cavity 110 in a first direction (X1 direction), while the end of the lower electrode 210 facing the first direction is suspended above the cavity 110 and does not extend laterally out of the cavity 110. That is, relative to the upper electrode extension 231 of the upper electrode 230 extending out of the cavity, the lower electrode 210 avoids extending into the cavity 110 below the upper electrode extension 231. Furthermore, the lower electrode extension 211 of the lower electrode 210 extends out of the cavity 110 in a second direction (Y1 direction), while the end of the upper electrode 230 facing the second direction is located above the cavity 110 and does not extend laterally out of the cavity 110. That is, relative to the lower electrode extension 211 of the lower electrode 210 extending out of the cavity, the upper electrode 230 avoids extending into the cavity 110 above the lower electrode extension 211. In this way, the upper electrode 230 and the lower electrode 210 do not overlap outside the cavity 110, eliminating the transverse modal mechanical vibration caused by the overlap of the upper electrode 230 and the lower electrode 210 outside the effective resonant region, thereby effectively reducing mechanical losses and improving the Q value of the device.

[0057] exist Figures 2-4In the example shown, the upper electrode 230 extends only from the cavity 110 to the upper electrode lead-out end used for electrical lead-out; that is, the upper electrode extension 231 only includes the upper electrode lead-out end for connection with the interconnect to electrically lead out the upper electrode 230. In this case, it is sufficient to limit the lower electrode 210 to the area of ​​the cavity 110 corresponding to the upper electrode extension 231. Figures 2-4 In the example shown, the lower electrode 210 does not extend beyond the cavity 110 at its ends in the X1, X2, and Y2 directions. However, in other examples, the lower electrode 210 can extend beyond the cavity 110 in more directions, bypassing the first direction. For example, even if the lower electrode 210 extends beyond the cavity 110 in both the X2 and Y2 directions, the upper electrode 230 and the lower electrode 210 will not overlap outside the cavity 110.

[0058] For example, another structure can be seen in Figure 6, in Figure 6 In the example shown, the upper electrode 230 extends out of the cavity 110 only at the upper electrode lead-out end (i.e., the upper electrode extension 231), and the lower electrode 210 extends out of the cavity 110 in the second direction (Y1 direction), the third direction (X2 direction), and the fourth direction (X2 direction). The portion of the lower electrode 210 extending out of the cavity 110 can overlap the edge of the cavity 110 to improve the support strength for the lower electrode 210 and the film layer above it.

[0059] Similarly, when the lower electrode 210 extends only its lower electrode lead-out end for electrical lead-out from the cavity 110, that is, the lower electrode extension 211 constitutes the lower electrode lead-out end for connection with the interconnect to electrically lead out the lower electrode 210, it is only necessary to limit the end of the upper electrode 230 corresponding to the lower electrode extension 211 to the area of ​​the cavity 110. Therefore, when only the lower electrode lead-out end of the lower electrode 210 extends out of the cavity 110, the distribution of the upper electrode 230 can be arranged more flexibly, so that the upper electrode 230 can also extend out of the cavity 110 in more directions. For example, even if the upper electrode 230 extends out of the cavity 110 in both the X2 and Y2 directions, the upper electrode 230 and the lower electrode 210 will not overlap outside the cavity 110.

[0060] In short, in this embodiment, the lower electrode 210 and the upper electrode 230 extend laterally out of the cavity 110 in mutually staggered directions, thereby ensuring the electrical lead-out of the upper and lower electrodes while avoiding overlap of the upper and lower electrodes outside the cavity 110. In an optional example, only the lead-out ends of the upper electrode 230 and the lower electrode 210 may extend laterally out of the cavity 110; that is, the upper electrode extension 231 may only include the upper electrode lead-out end, and the lower electrode extension 211 may only include the lower electrode lead-out end (e.g., ...). Figures 2-4 (as shown in the example); or in another example, the lower electrode 210 may also extend out of the cavity 110 in other directions (besides the direction from which the upper electrode extends) to overlap the edge of the cavity 110. For example, if the upper electrode extension 231 only includes the upper electrode lead-out end, the lower electrode extension 211 may include the lower electrode lead-out end, and may also include portions of the lower electrode 230 extending out of the cavity in other directions (e.g. Figure 6 (as shown in the example).

[0061] Specifically, the lower electrode 210 may include a lower electrode body and a lower electrode lead-out end that connects to the side of the lower electrode body and extends laterally out of the cavity. The upper electrode 230 may include an upper electrode body and an upper electrode lead-out end that connects to the side of the upper electrode body and extends laterally out of the cavity. The lower electrode body and the upper electrode body are primarily used to achieve their resonant function, while the lower electrode lead-out end and the upper electrode lead-out end are used to realize the electrical lead-out of the lower and upper electrodes, respectively. In this embodiment, the upper electrode 230 has its upper electrode body completely located directly above the cavity 110 without extending out of the cavity; in this case, the upper electrode extension 231 only includes the upper electrode lead-out end.

[0062] And in Figures 2-4 In the example shown, the lower electrode body is located directly above the cavity 110 without extending beyond it. The lower electrode body can be a polygonal structure (e.g., a pentagonal structure). The lower electrode lead-out end connects to one edge of the lower electrode body and extends laterally out of the cavity 110. In this case, the lower electrode extension 211 only includes the lower electrode lead-out end. Or in Figure 6 In the example shown, the lower electrode body portion is located directly above the cavity and extends out of the cavity 110 in both the X2 and Y2 directions. Its lower electrode lead-out end extends out of the cavity 110 in the Y1 direction. It can be considered that... Figure 6 The lower electrode extension 211 includes a lower electrode lead-out end and a portion of the lower electrode body extending out of the cavity.

[0063] It should be recognized that the lower electrode 210 in this embodiment can be flexibly adjusted according to the distribution area of ​​the upper electrode 210, provided that a support column 300 is additionally provided below the lower electrode 210. The presence of the support column 300 allows the edge of the lower electrode 210 to be suspended above the cavity 110. At the same time, by optimizing the setting method of the support column 300 in this embodiment, adverse effects on the resonance performance of the resonant structure can also be avoided.

[0064] Continue to refer to Figure 2 , Figure 5 and Figure 6 As shown, the support column 300 is disposed within the cavity 110 and located below the suspended end of the lower electrode 210, serving to support the lower electrode 210. In this embodiment, the support column 300 only supports the lower electrode 210 at its end, greatly reducing the impact on the resonant performance of the lower electrode 210 and the resonant structure it constitutes.

[0065] In a specific example, multiple support pillars 300 may be provided within the cavity 110, and the multiple support pillars 300 may be arranged sequentially along the end edge of the lower electrode 210. For example, see reference. Figure 2 In the example shown, the lower electrode 210 extends outside the cavity 110 only in the second direction (Y1 direction), while the ends facing other directions are all within the area of ​​the cavity 110. At this time, multiple support columns 300 are arranged sequentially along the edges of each end of the lower electrode 210 to ensure stable support for the lower electrode 210 and the film layer above it.

[0066] As described above, in a specific example, the lower electrode body of the lower electrode 210 is, for example, a polygonal structure (e.g., a pentagonal structure). When the lower electrode body is entirely disposed within the area of ​​the cavity, the support post 300 can be provided at each vertex of the polygonal structure of the lower electrode body to provide support at each vertex of the lower electrode body. Alternatively, in Figure 6 In the example shown, the lower electrode body portion of the lower electrode 210 extends out of the cavity. In this case, the support column 300 can be installed at the top corner position where the lower electrode body portion does not extend out of the cavity and is suspended in the air.

[0067] In an optional embodiment, the support post 300 is disposed outside the projection area of ​​the upper electrode 230, such that the upper electrode 230 does not cover the support post 300. Specifically, the support post 300 is disposed at the edge of the lower electrode body and does not correspond to the projection area of ​​the upper electrode 230. The support post 300 is disposed outside the projection area of ​​the upper electrode 230, for example, with the substrate surface as the projection plane, and the projection of the support post 300 on this projection plane is located outside the projection area of ​​the upper electrode 230 on this projection plane. As described above, the overlapping areas of the lower electrode 210, the piezoelectric material layer 220, the upper electrode 230, and the cavity 110 constitute an effective resonant region. Therefore, by disposing of the support post 300 outside the effective resonant region, the impact of the support post 300 on the resonant performance of the resonant structure is reduced to a greater extent, or even avoided altogether.

[0068] In this embodiment, a support portion 212 protruding towards the outer periphery of the cavity is provided on the suspended end of the lower electrode 210. That is, a support portion 212 is further provided on the suspended end of the lower electrode 210. The support portion 212 protrudes laterally towards the outer periphery of the cavity on its end side. The positions of the support portion 212 and the support column 300 are vertically corresponding, so that the support column 300 supports the support portion 212. In other words, by supporting the extended support portion 212, the support column 300 avoids supporting the main vibration area of ​​the lower electrode 210, further reducing the influence of the support column 300 on the resonance performance of the resonant structure. It should be understood that the support portion 212 formed by the extension of the lower electrode 210 is still located within the area of ​​the cavity 110. (Reference) Figure 2 and Figure 6 As shown, the support column 300 specifically supports the lower electrode 210 at its apex corner, thus allowing the apex corners of the pentagonal structure of the lower electrode 210 to protrude laterally to form the support portion 212. Furthermore, the support portion 212 protrudes laterally beyond the coverage area of ​​the upper electrode 230, ensuring that the upper electrode 230 does not cover the support portion 212.

[0069] Furthermore, the bulk acoustic wave filter also includes an upper electrode interconnect 420 and a lower electrode interconnect 410, wherein the upper electrode interconnect 420 is connected to the upper electrode lead-out terminal, and the lower electrode interconnect 410 is connected to the lower electrode lead-out terminal. The materials of the upper electrode interconnect 420 and the lower electrode interconnect 410 include, for example, metallic materials.

[0070] Based on the bulk acoustic wave filter described above, its fabrication method is explained in detail below. For specific details, please refer to... Figure 7 As shown, the method for preparing the bulk acoustic wave filter includes the following steps.

[0071] Step S100: A substrate is provided, in which a cavity is formed, and a sacrificial material layer is filled in the cavity.

[0072] Step S200: Form a support column in the sacrificial material layer.

[0073] In step S300, a lower electrode, a piezoelectric material layer, and an upper electrode are sequentially formed on the substrate to form a resonant structure.

[0074] Step S400: Remove the sacrificial material layer.

[0075] The following is combined with Figures 8-11 The fabrication method of the bulk acoustic wave filter in this embodiment will be further explained.

[0076] In step S100, please refer to the following for details. Figure 8 As shown, a substrate 100 is provided, in which a cavity 110 is formed, and a sacrificial material layer 500 is filled in the cavity 110. The sacrificial material layer 500 will be removed after the resonant structure is subsequently fabricated to release the cavity.

[0077] The method for forming the sacrificial material layer 500 includes, for example, depositing a sacrificial material (e.g., silicon oxide) on the substrate 100, the sacrificial material filling the cavity 110; then performing a planarization process (e.g., chemical mechanical polishing) to planarize the substrate surface, removing the sacrificial material from the substrate surface, such that the remaining sacrificial material only fills the cavity 110.

[0078] In step S200, please refer to the following for details. Figure 9 As shown, a support pillar 300 is formed in the sacrificial material layer 500. Specifically, the method for forming the support pillar 300 includes, for example, etching the sacrificial material layer 500 to form a through-hole, and filling the through-hole with a support material to form the support pillar 300. The material of the support pillar 300 includes, for example, silicon nitride.

[0079] In step S300, please refer to the following for details. Figure 10 As shown, a lower electrode 210, a piezoelectric material layer 220 and an upper electrode 230 are sequentially formed on the substrate 100 to form a resonant structure 200.

[0080] The method for forming the lower electrode 210 specifically includes: first, forming an electrode material layer on the substrate 100; then, patterning the electrode material layer to form the lower electrode 210. As described above, the lower electrode 210 is formed above the cavity 110 and has a lower electrode extension extending out of the cavity, and the end of the lower electrode 210 that does not extend out of the cavity covers the support post 300, so that after the sacrificial material layer 500 is subsequently removed, the lower electrode 210 can be supported by the support post 300.

[0081] In a specific example, the lower electrode 210 includes a lower electrode body for realizing the vibration function and a lower electrode lead-out end for realizing the electrical lead-out. In this case, only the lower electrode lead-out end can extend out of the cavity 110, and the lower electrode extension is the lower electrode lead-out end. Alternatively, the lower electrode body can also extend out of the cavity, and the lower electrode extension includes the lower electrode lead-out end and the part of the lower electrode body that extends out of the cavity.

[0082] In this embodiment, an upper electrode connection pad 421 for connecting with the upper electrode 230 is also formed on the substrate 100. The upper electrode connection pad 421 can assist in the electrical lead-out of the upper electrode 230. Specifically, the upper electrode connection pad 421 and the lower electrode 210 are formed using the same electrode material layer. That is, when performing a patterning process on the electrode material layer, a portion of the lower electrode 210 and a portion of the upper electrode connection pad 421 are retained to form mutually separated lower electrode 210 and upper electrode connection pad 421, respectively.

[0083] Furthermore, the piezoelectric material layer 220 covers the lower electrode layer 210 and the upper electrode connecting pad 421, and an upper electrode 230 is formed on the piezoelectric material layer 220. In this embodiment, the upper electrode 230 includes an upper electrode body portion for realizing the vibration function and an upper electrode lead-out end for realizing electrical lead-out. Only the upper electrode lead-out end may extend out of the cavity 110; in this case, the upper electrode extension portion is the upper electrode lead-out end. Further, the upper electrode lead-out end extends to the side of the upper electrode connecting pad 421 to facilitate the electrical connection between the upper electrode lead-out end and the upper electrode connecting pad 421.

[0084] In a further embodiment, after forming the upper electrode 230, the method further includes: etching the piezoelectric material layer 220 to form a first contact window (not shown) and a second contact window in the piezoelectric material layer 220, the first contact window exposing the lower electrode lead-out end, the second contact window exposing the upper electrode connecting pad 421, and the contact window also being close to the upper electrode lead-out end; forming a lower electrode interconnect 410 in the first contact window, the lower electrode interconnect 410 connecting the lower electrode lead-out end, and forming an upper electrode interconnect 420 in the second contact window, the bottom of the upper electrode interconnect 420 connecting the upper electrode connecting pad 421, and the top of the upper electrode interconnect 420 connecting the upper electrode lead-out end.

[0085] In step S400, please refer to the following for details. Figure 11 As shown, the sacrificial material layer 500 is removed to free up space in the cavity 110a. Specifically, the sacrificial material layer 500 can be removed by an etching process. Since the sacrificial material layer 500 and the support pillar 300 are made of different materials, the support pillar 300 is still retained after the sacrificial material layer is removed by etching to support the lower electrode 210 and the film layer above it.

[0086] In summary, the bulk acoustic wave filter provided in this embodiment utilizes support pillars within the cavity to support the lower electrode and its upper membrane layer. Compared to traditional processes where the lower electrode needs to extend beyond the cavity and be supported by the cavity's sidewalls, in this embodiment, the lower electrode can extend entirely beyond the cavity with the support pillars, effectively avoiding overlap between the upper and lower electrodes outside the cavity. This reduces mechanical energy loss caused by electrode overlap in non-effective resonant regions and improves the device's Q value.

[0087] It should be noted that although the present invention has been disclosed above with reference to preferred embodiments, these embodiments are not intended to limit the present invention. For any person skilled in the art, many possible variations and modifications can be made to the technical solutions of the present invention based on the disclosed technical content, or equivalent embodiments can be modified accordingly, without departing from the scope of the present invention. Therefore, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the present invention shall still fall within the scope of protection of the present invention.

[0088] It should also be understood that, unless otherwise specified or indicated, the terms “first,” “second,” “third,” etc., in the specification are used only to distinguish the various components, elements, and steps in the specification, and not to indicate the logical or sequential relationships between the various components, elements, and steps.

[0089] Furthermore, it should be recognized that the terminology described herein is used only to describe particular embodiments and not to limit the scope of the invention. It must be noted that the singular forms “a” and “an” used herein and in the appended claims include plural bases unless the context clearly indicates otherwise. For example, a reference to “a step” or “an apparatus” means a reference to one or more steps or apparatuses, and may include secondary steps and secondary apparatuses. All conjunctions used should be understood in the broadest sense. Also, the word “or” should be understood to have the definition of logical “or” rather than logical “exclusive OR”, unless the context clearly indicates otherwise. Furthermore, implementation of the methods and / or devices in embodiments of the invention may include performing selected tasks manually, automatically, or in combination.

Claims

1. A bulk acoustic wave filter, characterized in that, include: A substrate in which a cavity is formed; The resonant structure includes a lower electrode, a piezoelectric material layer, and an upper electrode sequentially disposed on the substrate. The upper electrode has an upper electrode extension extending out of the cavity, and the lower electrode has a lower electrode extension extending out of the cavity. The lower electrode extension and the upper electrode extension are offset from each other outside the cavity, and the end of the lower electrode that does not extend out of the cavity is suspended above the cavity. as well as, A support column is disposed within the cavity and located below the suspended end of the lower electrode to support the lower electrode. The lower electrode includes a lower electrode body and a lower electrode lead-out end that connects to the lower electrode body and extends out of the cavity; the upper electrode includes an upper electrode body and an upper electrode lead-out end that connects to the upper electrode body and extends out of the cavity. Wherein, the upper electrode extension includes the upper electrode lead-out end, and the lower electrode extension includes the lower electrode lead-out end; The support column is located outside the projection area of ​​the upper electrode body.

2. The bulk acoustic wave filter as described in claim 1, characterized in that, The upper electrode extension includes only the upper electrode lead-out end, and the lower electrode extension includes the lower electrode lead-out end and the portion of the lower electrode body extending out of the cavity.

3. The bulk acoustic wave filter as described in claim 1, characterized in that, Both the lower electrode body and the upper electrode body are positioned directly above the cavity.

4. The bulk acoustic wave filter as described in claim 1, characterized in that, The lower electrode body has a polygonal structure, and the support column is located below the apex corner of the polygonal structure.

5. The bulk acoustic wave filter according to any one of claims 1-4, characterized in that, The lower electrode has a support portion protruding towards the outer periphery of the cavity at its suspended end, and the support column is located below the support portion.

6. The bulk acoustic wave filter as described in claim 5, characterized in that, The overlapping area of ​​the lower electrode, the piezoelectric material layer, the upper electrode, and the cavity constitutes an effective resonant region, and the support protrudes beyond the effective resonant region.

7. A method for fabricating a bulk acoustic wave filter, characterized in that, include: A substrate is provided in which a cavity is formed, and the cavity is filled with a sacrificial material layer; Support columns are formed in the sacrificial material layer; A lower electrode, a piezoelectric material layer, and an upper electrode are sequentially formed on the substrate, wherein the upper electrode has an upper electrode extension extending out of the cavity, and the lower electrode has a lower electrode extension extending out of the cavity. The lower electrode extension and the upper electrode extension are offset from each other outside the cavity, and the end of the lower electrode that does not extend out of the cavity covers the support post; and... Remove the sacrificial material layer; The lower electrode includes a lower electrode body and a lower electrode lead-out end that connects to the lower electrode body and extends out of the cavity; the upper electrode includes an upper electrode body and an upper electrode lead-out end that connects to the upper electrode body and extends out of the cavity. Wherein, the upper electrode extension includes the upper electrode lead-out end, and the lower electrode extension includes the lower electrode lead-out end; The support column is located outside the projection area of ​​the upper electrode body.

8. The method for fabricating a bulk acoustic wave filter as described in claim 7, characterized in that, The method for forming the support post includes: etching the sacrificial material layer to form a through hole, and filling the through hole with a support material to form the support post.

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