CN115065338A - Bulk acoustic wave filter and method for manufacturing the same - Google Patents

Abstract

The invention provides a bulk acoustic wave filter and a preparation method thereof. By arranging 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 allowed to be suspended in the region of the cavity without being supported by the side wall of the cavity, and more It is flexibly realized that the lower electrode extension part and the upper electrode extension part are staggered outside the cavity, so that on the basis of realizing the electrical extraction of the upper and lower electrodes, the overlapping of the upper electrode and the lower electrode outside the cavity can be effectively avoided, reducing the The mechanical energy loss caused by the overlapping of the upper and lower electrodes in the non-effective resonance region is improved, and the Q value of the device is improved.

Description

Bulk acoustic wave filter and method of making the same

technical field

The invention relates to the technical field of semiconductors, in particular to a bulk acoustic wave filter and a preparation method thereof.

Background technique

The resonant structure made by utilizing the inverse piezoelectric effect of piezoelectric materials is the key element of crystal oscillators and filters, which are often used in bulk acoustic wave (BAW) filters. The construction methods of bulk acoustic wave filters mainly include air-gap type and solid-state assembly type (SMR). Among them, air-gap filters generally use MEMS manufacturing process to form an air gap in the substrate to confine acoustic waves to piezoelectric oscillations. among the piles. The structure has a high Q value and good mechanical strength.

Specifically, reference may be made to a schematic diagram of a bulk acoustic wave filter shown in FIG. 1 . The bulk acoustic wave filter includes resonant structures sequentially stacked on a substrate, and the resonant structures are at least located above the cavity 11 in the substrate. Specifically, the resonance structure includes a lower electrode 21 , a piezoelectric material layer 22 and an upper electrode 23 that are stacked in sequence, and the lower electrode 21 , the piezoelectric material layer 22 and the upper electrode 23 are in the cavity. The mutually overlapping regions just above 11 constitute the effective resonance region 20a of the resonance structure. The edge of the lower electrode 21 generally 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 to support the lower electrode 21 and the film layer above it. In addition, the upper electrode 23 also needs to extend laterally out of the cavity 11 to realize the electrical extraction of the upper electrode 23 .

However, the portion of the upper electrode 23 extending laterally out of the cavity will inevitably overlap with the portion of the lower electrode 21 mounted on the edge of the cavity. That is, the area of the upper electrode 23 and the lower electrode 21 outside the cavity 11 also overlaps spatially to form an extra-cavity overlapping area 20b, and the outer-cavity overlapping area 20b serves as an ineffective resonance area of the resonance structure, It will generate transverse modal mechanical vibration at the edge of the effective resonant region 20a, causing additional mechanical losses and generating some clutter, thereby reducing the Q value of the resonant structure.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a bulk acoustic wave filter, so as to reduce the mechanical loss generated by the bulk acoustic wave filter in the non-effective resonance region and improve the Q value of the device.

In order to solve the above technical problems, the present invention provides a bulk acoustic wave filter, comprising: a substrate, in which a cavity is formed; a resonance structure, including a lower electrode and a piezoelectric material sequentially arranged on the substrate layer and an upper electrode, 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 The extension parts are staggered 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; The lower electrode is positioned below the suspended end for supporting the lower electrode.

Optionally, the lower electrode includes a lower electrode body portion and a lower electrode lead-out end connected to a side of the lower electrode body portion and extending out of the cavity, and the upper electrode includes an upper electrode body portion and a side connected to the upper electrode body portion. edge and extend out of the upper electrode lead-out end of the cavity. Wherein, the upper electrode extension part includes the upper electrode lead-out end, and the lower electrode extension part includes the lower electrode lead-out end.

Optionally, the upper electrode extension part only includes the upper electrode lead-out end, and the lower electrode extension part includes the lower electrode lead-out end and the part of the lower electrode body extending out of the cavity.

Optionally, both the lower electrode body part and the upper electrode body part are completely disposed directly above the cavity.

Optionally, the lower electrode body portion is a polygonal structure, and the support column is disposed below a vertex position of the polygonal structure.

Optionally, the support column is disposed outside the projection area of the upper electrode body portion.

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 provided below the support portion.

Optionally, an area where the lower electrode, the piezoelectric material layer, the upper electrode and the cavity overlap each other constitute an effective resonance area, and the support portion protrudes beyond the effective resonance area.

Another object of the present invention is to provide a method for fabricating a bulk acoustic wave filter, including: providing a substrate, a cavity is formed in the substrate, and a sacrificial material layer is filled in the cavity; A support column is formed in the 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 an extension The lower electrode extension part extending out of the cavity, the lower electrode extension part and the upper electrode extension part are staggered from each other outside the cavity, and the end of the lower electrode that does not extend out of the cavity covers the support column and, removing the sacrificial material layer.

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

In the bulk acoustic wave filter provided by the present invention, the support column is arranged in the cavity to support the lower electrode and the film layer above it, so that the end of the lower electrode can be suspended in the area of the cavity without passing through the cavity The side wall of the body is supported, and the lower electrode extension part and the upper electrode extension part can be staggered outside the cavity more flexibly. In this way, on the basis of realizing the electrical extraction of the upper and lower electrodes, the upper The electrode and the lower electrode overlap each other outside the cavity, which reduces the mechanical energy loss caused by the overlapping of the upper and lower electrodes in the non-effective resonance region, and improves the Q value of the device.

Description of drawings

FIG. 1 is a top view of a conventional bulk acoustic wave filter.

FIG. 2 is a top view of the first bulk acoustic wave filter in an embodiment of the present invention.

3 is a schematic diagram of the lower electrode of the first bulk acoustic wave filter in an embodiment of the present invention.

FIG. 4 is a schematic diagram of an upper electrode of the first bulk acoustic wave filter in an embodiment of the present invention.

FIG. 5 is a schematic cross-sectional view of a bulk acoustic wave filter according to an embodiment of the present invention.

FIG. 6 is a top view of a second type of bulk acoustic wave filter in an embodiment of the present invention.

FIG. 7 is a schematic flowchart of a method for manufacturing a bulk acoustic wave filter according to an embodiment of the present invention.

8 to 11 are schematic structural diagrams of a bulk acoustic wave filter in an embodiment of the present invention during its manufacturing process.

Among them, the reference numerals are as follows:

11 - cavity;

21 - lower electrode;

22-piezoelectric material layer;

23-upper electrode;

20a-effective resonance region;

20b-overlapping region outside the cavity;

100-substrate;

110 - cavity;

200 - resonant structure;

210 - lower electrode;

211 - the lower electrode extension;

212 - support part;

220-piezoelectric material layer;

230-upper electrode;

231 - the upper electrode extension;

300 - support column;

410 - lower electrode interconnection line;

420-upper electrode interconnection line;

500 - Sacrificial Material Layer.

Detailed ways

The core idea of the present invention is to provide a bulk acoustic wave filter, the bulk acoustic wave filter is additionally provided with a support column for supporting below the suspended end of the lower electrode, so that at least part of the edge of the lower electrode can be retracted to Within the area of the cavity, the lower electrode and the upper electrode are prevented from overlapping each other outside the cavity, thereby eliminating the transverse modal mechanical vibration caused by the overlapping of the upper electrode and the lower electrode outside the effective resonance area, and reducing the mechanical loss. , improve the Q value of the device.

The bulk acoustic wave filter and its preparation method proposed by the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. The advantages and features of the present invention will become more apparent from the following description. It should be noted that, the accompanying drawings are all in a very simplified form and in inaccurate scales, and are only used to facilitate and clearly assist the purpose of explaining the embodiments of the present invention. It should be appreciated that relative terms such as "above," "below," "top," "bottom," "lateral," "above," and "below" as shown in the figures may be used to describe the relationship between relationship of various components. These relative terms are intended to encompass different orientations of the elements in addition to the orientation depicted in the figures. For example, if the device is turned over with respect to the view in the figures, elements described as "above" another element, for example, would now be below the element.

2 is a top view of the first bulk acoustic wave filter in an embodiment of the present invention, FIG. 3 is a schematic diagram of the lower electrode of the first bulk acoustic wave filter in an embodiment of the present invention, and FIG. 4 is the present invention A schematic diagram of an upper electrode of the first BAW filter in an embodiment, and FIG. 5 is a schematic cross-sectional view of the BAW filter in an embodiment of the present invention. FIG. 6 is a top view of a second type of bulk acoustic wave filter in an embodiment of the present invention.

First, as shown in FIG. 2 to FIG. 4 and FIG. 5 , the semiconductor structure in this embodiment includes: a substrate 100 and a resonance structure 200 formed on the substrate 100 .

In this embodiment, a cavity 110 is further formed in the substrate 100 , and the resonance structure 200 is formed at least above the cavity 110 . In this embodiment, the resonant structure 200 can be used to further constitute a thin film bulk acoustic resonator (Film Bulk Acoustic Resonator, FBAR).

Continuing to refer to FIG. 2 , the resonant structure 200 includes a lower electrode 210 , a piezoelectric material layer 220 and an upper electrode 230 which are sequentially arranged 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 lower electrode 210 , the piezoelectric material layer 220 , the area where the upper electrode 230 and the cavity 110 overlap each other constitutes an effective resonance area. Wherein, the materials of the lower electrode 210 and the upper electrode 230 may be the same, for example, both include molybdenum. And, the material of the piezoelectric material layer 220 includes, for example, at least one of zinc oxide (ZnO), aluminum nitride (AlN), and lead zirconate titanate (PZT).

Further, the upper electrode 230 has an upper electrode extension portion 231 extending out of the cavity 110 , the lower electrode 210 has a lower electrode extension portion 211 extending out of the cavity 110 , and the upper electrode extension portion 231 The lower electrode extension 211 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 located between the cavity 110 . staggered from each other. Specifically, the lower electrode 210 and the upper electrode 230 are partially located directly above the cavity 110, and are located in the orthographic projection area of the cavity 110; and the lower electrode 210 is also partially located from the cavity The lower electrode extension portion 211 is formed by the upper electrode 230 extending laterally out of the orthographic region of the cavity from the top of the body 110 . The upper electrode extending portion 231 is formed outside.

It should be noted that the "lateral extension" mentioned here specifically refers to extending in a direction parallel to the surface of the substrate. In addition, the "orthographic projection area" described here is, for example, a projection area where the surface of the substrate is used as a projection surface and is projected onto the projection surface.

That is, the lower electrode 210 and the upper electrode 230 only have overlapping regions above the cavity 110 , and there is no overlapping region 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 , and it can be considered that the upper electrode extension 231 extends above the suspended end of the lower electrode 210 The end of the upper electrode 230 corresponding to the lower electrode extension portion 211 is also restricted to be just above the cavity 110 and does not extend out of the cavity 110 .

In a specific example, the upper electrode extension portion 231 and the lower electrode extension portion 211 may extend out of the cavity 110 in different directions respectively. For example, in the example shown in FIG. 2 , the lower electrode extension portion 211 extends toward the cavity 110 . The upper electrode extending portion 231 extends in the second direction (Y1 direction), and the upper electrode extending portion 231 extends in the first direction (X1 direction). Alternatively, the upper electrode extension portion 231 and the lower electrode extension portion 211 extend out of the cavity 110 at positions parallel to the surface of the substrate and staggered from each other, for example, the upper electrode extension portion 231 and the lower electrode extension portion 231 The electrode extension parts 211 are arranged at positions shifted up and down on the paper shown in FIG. 2 .

In this embodiment, the upper electrode extension portion 231 and the lower electrode extension portion 211 extend out of the cavity 110 in different directions as an example for description. It should be noted that the “different directions” mentioned here refer to the specific directions of the electrodes extending, and the intersecting directions belong to different directions. For example, the X1 direction and the Y1 direction in FIG. They belong to different directions. For example, in FIG. 2 , the X1 direction and the X2 direction belong to different directions, and the Y1 direction and the Y2 direction belong to different directions.

Specifically, the upper electrode extension portion 231 of the upper electrode 230 extends out of the cavity 110 in the first direction (X1 direction), and at this time, the end of the lower electrode 210 facing the first direction is suspended in the above the cavity 110 without extending laterally out of the cavity 110 . That is, compared to the upper electrode extension portion 231 of the upper electrode 230 extending out of the cavity, the lower electrode 210 avoids extending out of the cavity 110 below the upper electrode extension portion 231 . And, the lower electrode extension portion 211 of the lower electrode 210 extends out of the cavity 110 in the second direction (Y1 direction), and the end of the upper electrode 230 facing the second direction is located in the cavity 110 at this time. above the cavity 110 without extending laterally. That is, in contrast to the lower electrode extension portion 211 of the lower electrode 210 extending out of the cavity, the upper electrode 230 avoids extending out of the cavity 110 above the lower electrode extension portion 211 . In this way, the upper electrode 230 and the lower electrode 210 do not have overlapping parts outside the cavity 110, and the transverse modal mechanical vibration generated by the overlapping of the upper electrode 230 and the lower electrode 210 outside the effective resonance region is eliminated. , which can effectively reduce the mechanical loss and improve the Q value of the device.

In the examples shown in FIGS. 2 to 4 , the upper electrode 230 only extends the upper electrode lead-out end for electrical extraction out of the cavity 110 , that is, the upper electrode extension 231 only includes the upper The electrode lead-out end is used for connecting with the interconnection wire to electrically lead out the upper electrode 230 . At this time, as long as the end of the lower electrode 210 corresponding to the upper electrode extension portion 231 is limited to the cavity 110 within the area. In the examples shown in FIGS. 2-4 , the ends of the lower electrode 210 in the X1 direction, the X2 direction and the Y2 direction do not extend out of the cavity 110 . However, in other examples, the lower electrode 210 can also be made to avoid the first direction and extend out of the cavity 110 in more directions. For example, the lower electrode 210 extends out of the cavity 110 even in the X2 direction and the Y2 direction. In the cavity 110 , there is still no situation that the upper electrode 230 and the lower electrode 210 overlap each other outside the cavity 110 .

For example, referring to another structure shown in FIG. 6 , in the example shown in FIG. 6 , only the upper electrode lead-out end (ie, the upper electrode extension 231 ) of the upper electrode 230 extends out of the cavity 110 , 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), and the lower electrode 210 extends out of the cavity 110 Part of the cavity 110 can be overlapped on the edge of the cavity 110 to improve the support strength for the lower electrode 210 and the film layer above it.

Similarly, when the lower electrode 210 only extends the lower electrode lead-out end for realizing electrical extraction out of the cavity 110 , that is, the lower electrode extension part 211 constitutes the lower electrode lead-out end for connecting with each other. The lower electrode 210 is electrically drawn out by connecting a wire. At this time, the end of the upper electrode 230 corresponding to the lower electrode extension portion 211 can be limited within the area of the cavity 110 . Therefore, in the case where only the leading end of the lower electrode extends out of the cavity 110 of the lower electrode 210, the distribution of the upper electrode 230 can also be set more flexibly, so that the upper electrode 230 can also be arranged in more directions It also extends out of the cavity 110. For example, even if the upper electrode 230 extends out of the cavity 110 in both the X2 direction and the Y2 direction, the upper electrode 230 and the lower electrode 210 will not interact with each other outside the cavity 110. overlapping cases.

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, so that on the basis of ensuring the electrical extraction of the upper and lower electrodes, It is avoided that the upper and lower electrodes overlap each other outside the cavity 110 . In an optional example, only the respective leading ends of the upper electrode 230 and the lower electrode 210 can extend laterally out of the cavity 110 , that is, the upper electrode extension part 231 only includes the upper electrode leading end, and the lower electrode extension part 211 only includes The lower electrode lead-out end (for example, in the examples shown in FIGS. 2-4 ); or in another example, the lower electrode 210 can also be extended out of the cavity 110 in other directions (except the direction in which the upper electrode extends) to Overlapped on the edge of the cavity 110, for example, in the case that the upper electrode extension part 231 only includes the upper electrode lead-out end, the lower electrode extension part 211 may include the lower electrode lead-out end, and may also include The lower electrode 230 extends out of the cavity in other directions (for example, in the example shown in FIG. 6 ).

Specifically, the lower electrode 210 may include a lower electrode body portion and a lower electrode lead-out end connected to the side of the lower electrode body portion and extending laterally out of the cavity, and the upper electrode 230 may include an upper electrode body portion and a lower electrode lead end connected to the upper electrode body portion. The side edge of the electrode body portion laterally extends out of the upper electrode lead-out end of the cavity. Wherein, the lower electrode body part and the upper electrode body part are mainly used to realize its resonance function, and the lower electrode lead-out end and the upper electrode lead-out end are used to realize the electrical extraction of the lower electrode and the upper electrode respectively. In the upper electrode 230 of the present embodiment, the upper electrode body portion is completely located directly above the cavity 110 and does not extend out of the cavity. At this time, the upper electrode extension portion 231 only includes the upper electrode lead-out end .

In the example shown in FIG. 2 to FIG. 4 , the lower electrode body is completely located directly above the cavity 110 without extending out of the cavity 110 , and the lower electrode body may be a polygonal structure ( For example, a pentagon structure), the lower electrode lead-out end is connected to one edge of the lower electrode body portion and extends laterally out of the cavity 110, at this time, the lower electrode extension portion 211 only includes the lower electrode lead-out end. Or in the example shown in FIG. 6 , the lower electrode body part is located directly above the cavity and extends out of the cavity 110 in the X2 direction and the Y2 direction, and the lower electrode lead-out end is in the Y1 direction Extending out of the cavity 110, it can be considered that the lower electrode extension part 211 in FIG. 6 includes the lower electrode lead-out end and the part of the lower electrode body extending out of the cavity.

It should be appreciated that the premise that the lower electrode 210 in this embodiment can flexibly adjust its distribution area according to the distribution area of the upper electrode 210 is that a support column 300 is additionally disposed below the lower electrode 210 , and the support column 300 The existence of , enables the edge of the lower electrode 210 to be suspended above the cavity 110 , and in this embodiment, by optimizing the arrangement of the support column 300 , adverse effects on the resonance performance of the resonant structure can be avoided.

Continuing to refer to FIG. 2 , FIG. 5 and FIG. 6 , the support column 300 is disposed in the cavity 110 and below the suspended end of the lower electrode 210 for supporting the lower electrode 210 . In this embodiment, the support column 300 only supports the lower electrode 210 at the end of the lower electrode 210 , which greatly reduces the influence on the resonance performance of the lower electrode 210 and the formed resonance structure.

In a specific example, a plurality of support columns 300 may be provided in the cavity 110 , and the plurality of support columns 300 are sequentially arranged along the edge of the end portion of the lower electrode 210 . For example, referring to the example shown in FIG. 2 , the lower electrode 210 only extends out of the cavity 110 in the second direction (Y1 direction), and the ends facing other directions are located within the area of the cavity 110 , At this time, the plurality of support columns 300 are sequentially arranged along the edge of each end portion of the lower electrode 210 to ensure stable support for the lower electrode 210 and the film layer above it.

As described above, in a specific example, the lower electrode body portion of the lower electrode 210 is, for example, a polygonal structure (eg, a pentagon structure). The support columns 300 are correspondingly arranged at each vertex position of the polygonal structure of the lower electrode body portion to support each vertex angle position of the lower electrode body portion. Alternatively, in the example shown in FIG. 6 , the lower electrode body portion of the lower electrode 210 extends out of the cavity. At this time, the lower electrode body portion can be set at the top corner position where the lower electrode body portion does not extend out of the cavity and is suspended in the air. Support column 300 .

In an optional solution, the support column 300 is disposed outside the projection area of the upper electrode 230 , so that the upper electrode 230 does not cover the support column 300 . Specifically, the support column 300 is disposed on the edge of the lower electrode body portion and does not correspond to the projection area of the upper electrode 230 . The support column 300 is arranged outside the projection area of the upper electrode 230, for example, the substrate surface is used as the projection surface, and the projection of the support column 300 on the projection surface is located on the upper electrode 230. outside the projection area of the projection surface. As described above, the overlapping region of the lower electrode 210, the piezoelectric material layer 220, the upper electrode 230 and the cavity 110 constitutes an effective resonance region. Therefore, the support column 300 is disposed in the Outside the effective resonance region, the influence of the support column 300 on the resonance performance of the resonance structure is reduced or even avoided to a greater extent.

In this embodiment, a support portion 212 protruding toward the outer periphery of the cavity is provided on the suspended end of the lower electrode 210 . That is, a supporting portion 212 is further provided on the suspended end of the lower electrode 210, and the supporting portion 212 protrudes laterally on the side surface of the end portion toward the outer periphery of the cavity. The supporting portion 212 and the supporting column The positions of 300 correspond up and down, so that the support column 300 supports the support portion 212 . That is, by supporting the extended support portion 212, the support column 300 avoids supporting the main vibration area of the lower electrode 210, and further reduces the influence of the support column 300 on the resonance performance of the resonance structure. It should be appreciated that the support portion 212 formed by the extension of the lower electrode 210 is still located within the area of the cavity 110 . Referring to FIG. 2 and FIG. 6 , the support column 300 is specifically supported at the top corner of the lower electrode 210 , so the top corners of the pentagon structure of the bottom electrode 210 can be laterally protruded to form the support Section 212. In addition, the support portion 212 laterally protrudes beyond the coverage area of the upper electrode 230 , so that the upper electrode 230 does not cover the support portion 212 .

Further, the bulk acoustic wave filter further includes an upper electrode interconnection line 420 and a lower electrode interconnection line 410, the upper electrode interconnection line 420 is connected to the upper electrode terminal, and the lower electrode interconnection line is connected to the The lower electrode lead-out terminal. Wherein, the materials of the upper electrode interconnection lines 420 and the lower electrode interconnection lines 410 include, for example, metal materials.

Based on the bulk acoustic wave filter as described above, the manufacturing method thereof will be described in detail below. Specifically, as shown in FIG. 7 , the preparation method of the bulk acoustic wave filter includes the following steps.

In step S100, a substrate is provided, a cavity is formed in the substrate, and a sacrificial material layer is filled in the cavity.

Step S200, forming a support column in the sacrificial material layer.

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

Step S400, removing the sacrificial material layer.

The manufacturing method of the bulk acoustic wave filter in this embodiment will be further described below with reference to FIG. 8 to FIG. 11 .

In step S100 , referring specifically to FIG. 8 , a substrate 100 is provided, a cavity 110 is formed in the substrate 100 , and a sacrificial material layer 500 is filled in the cavity 110 . The sacrificial material layer 500 will be removed after the subsequent fabrication of the resonant structure to release the cavity.

The method for forming the sacrificial material layer 500 includes, for example: depositing a sacrificial material (eg, including silicon oxide) on the substrate 100 , the sacrificial material filling the cavity 110 ; and then performing a planarization process (eg, chemical mechanical polishing process) to planarize the substrate surface and remove the sacrificial material on the substrate surface, so that the remaining sacrificial material is only filled in the cavity 110 .

In step S200 , with specific reference to FIG. 9 , a support column 300 is formed in the sacrificial material layer 500 . Specifically, the method for forming the support column 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 column 300 . Wherein, the material of the support column 300 includes, for example, silicon nitride.

In step S300 , referring specifically to FIG. 10 , a lower electrode 210 , a piezoelectric material layer 220 and an upper electrode 230 are sequentially formed on the substrate 100 to form the resonance structure 200 .

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 portion extending out of the cavity, and the end portion of the lower electrode 210 that does not extend out of the cavity covers the support column 300 , Therefore, after the sacrificial material layer 500 is subsequently removed, the support column 300 can be used to support the lower electrode 210 .

In a specific example, the lower electrode 210 includes a lower electrode body portion for realizing a vibration function and a lower electrode lead-out end for realizing electrical extraction, wherein only the lower electrode lead-out end can be extended out of the cavity 110 . At this time, the lower electrode The extension part is the lead-out end of the lower electrode; alternatively, the lower electrode body part can also be partially extended out of the cavity, in this case the lower electrode extension part includes the lead-out end of the lower electrode and the part of the lower electrode body part extending out of the cavity.

In this embodiment, an upper electrode connection pad 421 for connecting with the upper electrode 230 is further formed on the substrate 100 , and the upper electrode connection pad 421 can assist in realizing the electrical extraction of the upper electrode 230 . Specifically, the upper electrode connection pad 421 and the lower electrode 210 are formed by using the same electrode material layer, that is, when the electrode material layer is patterned, part of the lower electrode 210 and the upper electrode connection pad 421 are retained. part to form the lower electrode 210 and the upper electrode connection pad 421 which are separated from each other.

And, the piezoelectric material layer 220 covers the lower electrode layer 210 and the upper electrode connection pad 421, and an upper electrode 230 is formed on the piezoelectric material layer 220. In this embodiment, the upper electrode 230 It includes an upper electrode body part for realizing the vibration function and an upper electrode lead-out end for realizing electrical extraction, wherein only the upper electrode lead-out end can be extended out of the cavity 110, and the upper electrode extension part is the upper electrode lead-out end at this time. . Further, the upper electrode leading end extends to the side of the upper electrode connecting pad 421 to facilitate electrical connection between the upper electrode leading end and the upper electrode connecting pad 421 .

In a further solution, after the upper electrode 230 is formed, the method further includes: etching the piezoelectric material layer 220 to form a first contact window (not shown in the figure) and a second contact window, the first contact window exposes the lower electrode lead end, the second contact window exposes the upper electrode connection pad 421, and the contact window is also close to the upper electrode lead end; A lower electrode interconnection line 410 is formed in the first contact window, the lower electrode interconnection line 410 is connected to the lower electrode terminal, an upper electrode interconnection line 420 is formed in the second contact window, and the lower electrode interconnection line 410 is formed in the second contact window. The bottom of the upper electrode interconnection line 420 is connected to the upper electrode connection pad 421 , and the top of the upper electrode interconnection line 420 is connected to the upper electrode lead-out terminal.

In step S400, referring specifically to FIG. 11, the sacrificial material layer 500 is removed to release the space of the cavity 110a. Specifically, the sacrificial material layer 500 may be removed by an etching process, and the materials of the sacrificial material layer 500 and the support pillars 300 are different. After the sacrificial material layer is removed by etching, the support pillars 300 are still retained for supporting the lower electrode 210 and the film layer above it.

To sum up, in the bulk acoustic wave filter provided in this embodiment, the support column is arranged in the cavity, so that the lower electrode and the film layer above it are supported in the cavity by the support column. Compared with the need to extend the lower electrode out of the cavity to support the lower electrode by the side wall of the cavity in the traditional process, the lower electrode in this embodiment can be supported by the support column and does not necessarily need to extend completely out of the cavity. , effectively avoiding the overlapping of the upper electrode and the lower electrode outside the cavity, reducing the mechanical energy loss caused by the overlapping of the upper and lower electrodes in the non-effective resonance area, and improving the Q value of the device.

It should be noted that, although the present invention has been disclosed above with preferred embodiments, the above embodiments are not intended to limit the present invention. For any person skilled in the art, without departing from the scope of the technical solution of the present invention, many possible changes and modifications can be made to the technical solution of the present invention by using the technical content disclosed above, or modified into equivalents of equivalent changes. Example. Therefore, any simple modifications, equivalent changes and modifications made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solutions of the present invention still fall within the protection scope of the technical solutions of the present invention.

It should also be understood that unless otherwise specified or indicated, the terms "first", "second", "third" and other descriptions in the specification are only used to distinguish various components, elements, steps, etc. in the specification, rather than It is used to represent the logical relationship or sequence relationship among various components, elements, steps, etc.

Also, it should be appreciated that the terminology described herein is used to describe particular embodiments only, and not to limit the scope of the present invention. It must be noted that, as used herein and in the appended claims, the singular forms "a" and "an" include plural references unless the context clearly dictates otherwise. For example, reference to "a step" or "a means" means a reference to one or more steps or means, and may include sub-steps as well as sub-means. All conjunctions used should be understood in their broadest sense. Also, the word "or" should be understood to have the definition of a logical "or" rather than a logical "exclusive or" unless the context clearly dictates otherwise. Furthermore, implementation of methods and/or apparatuses in embodiments of the present invention may include performing selected tasks manually, automatically, or a combination.

Claims (10)

1. a bulk acoustic wave filter, is characterized in that, comprises: a substrate, a cavity is formed in the substrate; A resonance structure includes a lower electrode, a piezoelectric material layer and an upper electrode sequentially arranged on the substrate, the upper electrode has an upper electrode extension extending out of the cavity, and the lower electrode has an extension extending out of the cavity The lower electrode extension part of the cavity, the lower electrode extension part and the upper electrode extension part are staggered from each other outside the cavity, and the end of the lower electrode that does not extend out of the cavity is suspended at the end of the cavity. above; and, A support column is arranged in the cavity and located below the suspended end of the lower electrode, and is used for supporting the lower electrode. 2 . The BAW filter according to claim 1 , wherein the lower electrode comprises a lower electrode body portion and a lower electrode lead-out end connected to the lower electrode body portion and extending out of the cavity, and the upper electrode includes an upper electrode body portion. 3 . an electrode body part and an upper electrode lead-out end connected to the upper electrode body part and extending out of the cavity; Wherein, the upper electrode extension part includes the upper electrode lead-out end, and the lower electrode extension part includes the lower electrode lead-out end. 3 . The BAW filter according to claim 2 , wherein the upper electrode extension part only includes the upper electrode lead end, and the lower electrode extension part includes the lower electrode lead end and the lower electrode lead end. 4 . The electrode body portion extends out of the cavity. 4 . The BAW filter according to claim 2 , wherein the lower electrode body portion and the upper electrode body portion are both completely disposed directly above the cavity. 5 . 5 . The BAW filter according to claim 2 , wherein the lower electrode body portion is a polygonal structure, and the support column is disposed below the vertex position of the polygonal structure. 6 . 6 . The BAW filter according to claim 2 , wherein the support column is disposed outside the projection area of the upper electrode body portion. 7 . 7 . The BAW filter according to claim 1 , wherein the suspended end of the lower electrode is provided with a support portion protruding toward the outer periphery of the cavity, and the support column arranged below the support portion. 8 . The BAW filter according to claim 7 , wherein the region where the lower electrode, the piezoelectric material layer, the upper electrode and the cavity overlap each other constitutes an effective resonance region, and the The support portion protrudes out of the effective resonance area. 9. a preparation method of bulk acoustic wave filter, is characterized in that, comprises: providing a substrate having a cavity formed therein and filling the cavity with a layer of sacrificial material; forming support posts 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 extending portion extending out of the cavity, and the lower electrode has a lower electrode extending out of the cavity an electrode extension part, the lower electrode extension part and the upper electrode extension part are staggered from each other outside the cavity, and the end of the lower electrode that does not extend out of the cavity covers the support column; and, The sacrificial material layer is removed. 10 . The method for manufacturing a bulk acoustic wave filter according to claim 9 , wherein the method for forming the support column comprises: etching the sacrificial material layer to form a through hole, and filling the through hole in the through hole. 11 . support material to form the support posts.

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