MEMS structure and preparation method thereof, MEMS piezoelectric microphone

Abstract

The present invention provides a MEMS structure and a preparation method thereof, a MEMS piezoelectric microphone. The MEMS structure comprises: a substrate, comprising: an outer substrate ring body; a substrate back cavity formed inside the substrate outer ring body; a vibration support layer formed above the substrate outer ring body and the substrate back cavity; a piezoelectric composite layer, comprising: a lower electrode layer, a piezoelectric layer, and an upper electrode layer, the three being formed in sequence above the vibration support layer, and the horizontal plane projection of the piezoelectric layer is located in the middle area of ​​the horizontal plane projection of the substrate back cavity; wherein, in the horizontal direction, the vibration support layer comprises: a connection stabilization area and a vibration enhancement area, the connection stabilization area being the area corresponding to the edge position of the piezoelectric layer; the vibration enhancement area being the area away from the edge position of the piezoelectric layer; the connection stabilization area protruding downward in a ring shape, and its thickness H1 is greater than the thickness H2 of the vibration enhancement area. While taking into account the reliability of the MEMS structure, the present invention improves the sensitivity of the device.

Description

Technical Field

[0001] The present invention relates to the technical fields of novel electroacoustic component manufacturing and microelectronic devices, and in particular to a MEMS structure and a preparation method thereof, and a MEMS piezoelectric microphone. Background Art

[0002] MEMS (Micro-Electro-Mechanical System) microphones are a new type of electroacoustic component manufactured using micromachining technology. They are characterized by small size, excellent frequency response, and low noise. As smart electronic devices become smaller and thinner, MEMS microphones are increasingly used in these devices.

[0003] MEMS microphones primarily include capacitive and piezoelectric types. MEMS piezoelectric microphones utilize micro-electromechanical systems (MEMS) and piezoelectric thin film technologies. Their use of semiconductor planar processing and bulk silicon processing allows for compact size, compact volume, and excellent consistency. Compared to capacitive microphones, they also offer advantages such as requiring no bias voltage, a wide operating temperature range, and dust and water resistance. However, their relatively low sensitivity has hampered their development.

[0004] In the existing technology, based on the piezoelectric single-chip microphone structure, the device sensitivity is closely related to the vibration displacement of the vibration support layer. Currently, the vibration displacement of the vibration support layer of the piezoelectric microphone needs to be further improved to enhance the device sensitivity. Summary of the Invention

[0005] (1) Technical issues to be resolved

[0006] In order to at least partially solve one of the above technical problems, the present invention provides a MEMS structure and a preparation method thereof, and a MEMS piezoelectric microphone.

[0007] (2) Technical solution

[0008] In the first aspect of the present invention, a MEMS structure is provided, comprising: a substrate, comprising: an outer substrate ring body; a substrate back cavity formed on the inner side of the substrate outer ring body; a vibration support layer, formed above the substrate outer ring body and the substrate back cavity; a piezoelectric composite layer, comprising: a lower electrode layer, a piezoelectric layer, and an upper electrode layer, the three being formed in sequence above the vibration support layer, and the horizontal plane projection of the piezoelectric layer is located in the middle area of ​​the horizontal plane projection of the substrate back cavity; wherein, in the horizontal direction, the vibration support layer comprises: a connection stabilization area and a vibration enhancement area, the connection stabilization area is an area of ​​the vibration support layer corresponding to the edge position of the piezoelectric layer; the vibration enhancement area is an area of ​​the vibration support layer away from the edge position of the piezoelectric layer; wherein, on the side away from the substrate back cavity, the vibration support layer is flat as a whole; on the side close to the substrate back cavity, the connection stabilization area is annular and protrudes downward, and its thickness H1 is greater than the thickness H2 of the vibration enhancement area.

[0009] In some embodiments of the present invention, the lower electrode layer is formed directly above the vibration support layer and extends in a first direction outside the vibration support layer; the longitudinal section of the upper electrode layer is in the shape of a "Z" or a left-right mirrored "Z" shape, the upper portion of which is formed above the piezoelectric layer, and the lower portion of which is formed directly above the vibration support layer, extending in a second direction outside the vibration support layer, and staggered with the lower electrode layer; wherein the horizontal plane projection of the portion of the lower electrode layer below the piezoelectric layer at least partially overlaps with the horizontal plane projection of the portion of the upper electrode layer above the piezoelectric layer.

[0010] In a second aspect of the present invention, a MEMS piezoelectric microphone is provided, comprising: a MEMS structure as described above, wherein an upper electrode layer and a lower electrode layer are connected to the output end of the MEMS piezoelectric microphone; wherein the vibration support layer senses sound waves, driving the piezoelectric composite layer to vibrate; and the piezoelectric layer senses the electrical signal generated by the strain, which is output to the outside through the upper electrode layer and the lower electrode layer.

[0011] In a third aspect of the present invention, a method for preparing the above MEMS structure is provided, comprising:

[0012] Step A, depositing a sacrificial layer on a substrate;

[0013] Step B, patterning the sacrificial layer to form an annular groove at the location of the preset connection stabilization area;

[0014] Step C, depositing a vibration support layer on the sacrificial layer having the annular groove, and planarizing the upper surface thereof; wherein the vibration support layer corresponding to the annular groove forms a connection stabilization area; and the vibration support layer corresponding to the non-annular groove portion forms a vibration reinforcement area;

[0015] Step D, forming a lower electrode layer, a piezoelectric layer, and an upper electrode layer in sequence on the vibration support layer after the upper surface is planarized;

[0016] Step E: deeply etching the inner side of the back surface of the substrate to the vibration support layer to form a substrate back cavity;

[0017] Step F, removing the sacrificial layer below the vibration support layer.

[0018] In some embodiments of the present invention, step D includes: sub-step D1, depositing a lower electrode layer on the vibration support layer after the upper surface is planarized; sub-step D2, patterning the lower electrode layer so that it covers a preset area of ​​the piezoelectric layer and extends in a first direction toward the outside of the vibration support layer, exposing the vibration support layer area extending in a second direction toward the outside of the vibration support layer; sub-step D3, depositing the piezoelectric layer on the lower electrode layer, and retaining only the piezoelectric layer in the preset area by patterning; sub-step D4, depositing the upper electrode layer on the piezoelectric layer and the exposed vibration support layer area.

[0019] In some embodiments of the present invention, sub-step D4 also includes: sub-step D5, depositing an electrode thickening layer on the lower electrode layer and the upper electrode layer, and obtaining a lower electrode thickening layer electrically connected to the lower electrode layer and an upper electrode thickening layer electrically connected to the upper electrode layer by patterning them.

[0020] In some embodiments of the present invention, in step E, the horizontal plane projection of the substrate back cavity is a circle with a radius of R; in step C, for the vibration support layer: the thickness connecting the stable area and the vibration enhancement area satisfies: 1 / 3H1≤H2

[0021] In some embodiments of the present invention, for the vibration support layer, 300 nm ≤ H1 ≤ 2000 nm; 100 nm ≤ L1 ≤ 500 nm.

[0022] In some embodiments of the present invention, the horizontal projection of the piezoelectric layer is a circle with a radius R1 that satisfies:

[0023]

[0024] In some embodiments of the present invention, the longitudinal section of the connection stabilization zone is a rectangle or an inverted isosceles triangle.

[0025] In some embodiments of the present invention, the substrate is one of the following: a silicon wafer, an SOI substrate, or polysilicon on SiO 2 / Si.

[0026] In some embodiments of the present invention, the vibration support layer is a single-layer film or a multi-layer film, and its material is one or more of the following: silicon nitride, silicon oxide, single crystal silicon, and polycrystalline silicon.

[0027] ​In some embodiments of the present invention, the thickness of the piezoelectric layer is between 0.1 μm and 10 μm, and the material thereof is selected from one or more of the following: aluminum nitride, scandium-doped aluminum nitride, zinc oxide, and lead zirconate titanate.

[0028] In some embodiments of the present invention, the thickness of the upper electrode layer and the lower electrode layer is between 20 nm and 200 nm, and the materials thereof are selected from one or more of the following: molybdenum, gold, aluminum, and chromium.

[0029] (3) Beneficial effects

[0030] It can be seen from the above technical solutions that the present invention has at least one of the following beneficial effects compared to the prior art:

[0031] (1) According to the process capability, the vibration support layer is prepared into a film layer with non-uniform thickness, showing thickness variation. The vibration support layer is thick at the edge of the piezoelectric composite layer, while it is thin in other areas. The advantages are: ① The thinning of the vibration support layer increases the vibration displacement of the entire vibration support layer, the increased deformation of the piezoelectric layer, and the increase in the output of the piezoelectric signal; ② The vibration support layer is thick at the edge of the piezoelectric composite layer, which increases the stability of the vibration support layer.

[0032] (2) The ring structure of the vibration support layer close to the back cavity side of the substrate increases the strength of the vibration support layer, thereby improving the reliability of the MEMS structure.

[0033] (3) The use of a sacrificial layer to prepare a vibration support layer with varying thickness is less expensive and easier to implement than other methods in the prior art.

[0034] (4) The upper electrode layer has a longitudinal cross-section that is a "Z" shape or a mirrored "Z" shape. The upper portion of the upper electrode layer is formed above the piezoelectric layer, and the lower portion of the upper electrode layer is formed directly above the vibration support layer. The upper electrode layer extends in a second direction toward the outside of the vibration support layer and is offset from the lower electrode layer. This arrangement allows both the upper and lower electrode layers to output from above the vibration support layer, increasing the flexibility of circuit design.

[0035] (5) A thickening layer is added to the upper and lower electrode layers, and the top of the thickening layer is flush with the top of the upper electrode layer, thereby achieving flattening of the entire MEMS structure and facilitating wiring. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 and Figure 2 They are respectively a stereoscopic view and a cross-sectional view of the MEMS structure according to an embodiment of the present invention.

[0037] Figures 3A to 3H For preparation Figure 1 、 Figure 2 Cross-sectional view of the device after various steps in the MEMS structure process are shown. DETAILED DESCRIPTION

[0038] The inventive concept of this invention lies in improving the thickness of the vibration support layer to produce a non-uniform membrane layer. The vibration support layer is thick at the edge of the piezoelectric composite layer and thin in other areas. This improves the sensitivity of the device while maintaining the reliability of the MEMS structure.

[0039] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with specific implementation methods and with reference to the accompanying drawings.

[0040] According to the first and second aspects of the present invention, a MEM structure and a method for preparing the same are provided. Figure 1 and Figure 2 They are respectively a stereoscopic view and a cross-sectional view of the MEMS structure according to an embodiment of the present invention. Figure 1 、 Figure 2 As shown, the MEMS structure of this embodiment includes:

[0041] The substrate 10 includes: a substrate outer ring body 11 on the periphery; a substrate back cavity 12 formed inside the substrate outer ring body;

[0042] The vibration support layer 20 is formed above the substrate outer ring and the substrate back cavity;

[0043] The piezoelectric composite layer 30 includes a lower electrode layer 31, a piezoelectric layer 32, and an upper electrode layer 33, which are sequentially formed above the vibration support layer, and the horizontal projection of the piezoelectric layer is located in the middle area of ​​the horizontal projection of the substrate back cavity;

[0044] The following is a detailed description of each component of the MEM structure of this embodiment.

[0045] Please refer to Figure 1 and Figure 2 The horizontal projection of the substrate back cavity 12 is a circle with a radius of R; the horizontal projection of the piezoelectric layer 32 is a circle with a radius of R1, R1 < R. Further,

[0046] 1. Vibration support layer with varying thickness

[0047] One of the characteristics of the present invention is that the vibration support layer exhibits variable thickness. Specifically, it is thicker at the edges of the piezoelectric composite layer and thinner in other areas, thereby increasing the vibration displacement of the entire vibration support layer while also improving the stability of the vibration support layer.

[0048] Please refer to Figure 2Horizontally, the vibration support layer 20 comprises a connecting stabilization region 21 and a vibration enhancement region 22. The connecting stabilization region 21 corresponds to the edge of the piezoelectric layer, while the vibration enhancement region 22 is located further away from the edge of the piezoelectric layer. On the side away from the substrate back cavity, the vibration support layer is generally flat. On the side closer to the substrate back cavity, the connecting stabilization region 21 protrudes downward in a circular shape, with a thickness H1 greater than the thickness H2 of the vibration enhancement region.

[0049] Furthermore, the thickness of each part of the vibration support layer 20 satisfies: 1 / 3 H1≤H2

[0050] Furthermore, the ring width L1 of the ring connecting the stabilization area 21 in the vibration support layer satisfies: 1 / 10R≤L1≤1 / 4R. From a specific numerical point of view, 100nm≤L1≤500nm.

[0051] Furthermore, for the connection stabilization area 21, its cross section can be a rectangle or an inverted isosceles triangle.

[0052] From the above description, it can be seen that in the present invention, according to the process capabilities, the vibration support layer is prepared into a film layer with non-uniform thickness, showing thickness variation. The vibration support layer is thick at the edge of the piezoelectric composite layer, while the vibration support layer is thin in other areas. The advantages are: ① The vibration support layer becomes thinner, which increases the vibration displacement of the entire vibration support layer, and the increased deformation of the piezoelectric layer increases the output of the piezoelectric signal; ② The vibration support layer is thick at the edge of the piezoelectric composite layer, which increases the stability of the vibration support layer; further, the vibration support layer is close to the annular structure on the side of the substrate back cavity, which increases the strength of the vibration support layer, thereby improving the reliability of the MEMS structure.

[0053] 2. Using a sacrificial layer to achieve thickness changes in the vibration support layer

[0054] The second feature of the present invention is to use a sacrificial layer to achieve thickness variation of the vibration support layer. The specific preparation process will be described in detail in the preparation method embodiment. Here we only introduce the sacrificial layer retained in the finished MEMS structure. Please refer to Figure 2 A sacrificial layer 23 is left between the substrate outer ring 11 and the vibration support layer 20 .

[0055] 3. Upper electrode layer of the "Z"-shaped longitudinal section

[0056] The third feature of the present invention is the design of the upper electrode layer. By designing the upper electrode layer into a "Z" shape, the subsequent circuit design is facilitated.

[0057] Please refer to Figure 2 ​The lower electrode layer 31 is formed directly above the vibration support layer and extends in a first direction outward from the vibration support layer. The upper electrode layer 33 has a longitudinal cross-section that is a mirror image of a "Z" shape. Its upper portion 33a is formed above the piezoelectric layer, and its lower portion 33c is formed directly above the vibration support layer, extending in a second direction outward from the vibration support layer and offset from the lower electrode layer. The middle portion 33b is located on the side of the piezoelectric layer and is separated from the lower electrode layer by the piezoelectric layer. Furthermore, the horizontal projection of the portion of the lower electrode layer below the piezoelectric layer at least partially overlaps with the horizontal projection of the portion of the upper electrode layer above the piezoelectric layer.

[0058] Through such an arrangement, both the upper electrode layer and the lower electrode layer are output from above the vibration support layer, thereby increasing the flexibility of circuit design.

[0059] Those skilled in the art should understand that although the longitudinal cross-section of the upper electrode layer in this embodiment is a "Z" shape with left and right mirror images, in other embodiments of the present invention, the longitudinal cross-section of the upper electrode layer can also be a "Z" shape. As long as the upper electrode is introduced into the vibration support layer below, it is within the scope of protection of the present invention.

[0060] 4. Electrode Thickening Layer

[0061] After guiding both the upper and lower electrode layers to the vibration support layer, a lower electrode thickening layer 41 is formed on the lower electrode outside the vibration support layer. An upper electrode thickening layer 42 is formed on the upper electrode outside the vibration support layer. The tops of the upper and lower electrode thickening layers are flush with the top of the upper electrode layer. This arrangement flattens the entire MEMS structure and facilitates wiring.

[0062] 5. Material and thickness

[0063] In this embodiment, the substrate is one of the following: a silicon wafer, an SOI substrate, or polysilicon on SiO2 / Si.

[0064] In this embodiment, the material of the sacrificial layer 23 is silicon oxide.

[0065] In this embodiment, the vibration support layer is a single-layer film or a multi-layer film, and its material is one or more of the following: silicon nitride, silicon oxide, single crystal silicon, and polycrystalline silicon.

[0066] In this embodiment, the thickness of the piezoelectric layer is between 0.1 μm and 10 μm, and the material thereof is selected from one or more of the following: aluminum nitride, scandium-doped aluminum nitride, zinc oxide, and lead zirconate titanate.

[0067] In this embodiment, the thickness of the upper electrode layer and the lower electrode layer is between 20 nm and 200 nm, and the materials thereof are selected from one or more of the following: molybdenum, gold, aluminum, and chromium.

[0068] The following introduction Figure 1、 Figure 2 Preparation method of the MEMS structure shown.

[0069] Figures 3A to 3H For preparation Figure 1 、 Figure 2 The device cross-section after each step in the MEMS structure process is shown. Figures 3A to 3H , the preparation method comprises:

[0070] Step A, depositing a sacrificial layer on a substrate;

[0071] In this embodiment, the substrate is one of the following: a silicon wafer, an SOI substrate, or polysilicon on SiO2 / Si. The material of the sacrificial layer is silicon oxide.

[0072] Step B: Patterning the sacrificial layer to form an annular groove at the location of the preset connection stability area, such as Figure 3A As shown;

[0073] The shape of the annular groove will determine the shape of the lower surface of the subsequent vibration support layer. Therefore, the shape of the groove needs to be determined according to the preset shape of the lower surface of the vibration support layer.

[0074] Step C: depositing a vibration support layer on the sacrificial layer having the annular groove and planarizing the upper surface thereof, as shown in FIG. Figure 3B As shown;

[0075] The vibration support layer corresponding to the annular groove forms a connection stable area; the vibration support layer corresponding to the non-annular groove portion forms a vibration strengthening area;

[0076] In this step, for the vibration support layer, the thickness connecting the stabilizing area and the vibration enhancing area satisfies: 1 / 3 H1 ≤ H2 < H1; the width L1 of the ring connecting the stabilizing area satisfies: 1 / 10 R ≤ L1 ≤ 1 / 4 R. Furthermore, for the vibration support layer, 300 nm ≤ H1 ≤ 2000 nm; and 100 nm ≤ L1 ≤ 500 nm.

[0077] In this step, the vibration support layer is a single-layer film or a multi-layer film, and its material is one or more of the following: silicon nitride, silicon oxide, single crystal silicon, and polycrystalline silicon.

[0078] Step D, forming a lower electrode layer, a piezoelectric layer, and an upper electrode layer in sequence on the vibration support layer after the upper surface is planarized;

[0079] Furthermore, the step D comprises:

[0080] Sub-step D1, depositing a lower electrode layer on the vibration support layer after the upper surface is planarized;

[0081] Sub-step D2, patterning the lower electrode layer so that it covers the preset area of ​​the piezoelectric layer and extends in a first direction toward the outside of the vibration support layer, exposing the vibration support layer area extending in a second direction toward the outside of the vibration support layer, such as Figure 3C As shown;

[0082] Sub-step D3, depositing a piezoelectric layer on the lower electrode layer, and retaining only the piezoelectric layer in a predetermined area by patterning, such as Figure 3D As shown;

[0083] For the piezoelectric layer, its horizontal plane projection is a circle with a radius of R1 that satisfies:

[0084] Sub-step D4, depositing an upper electrode layer on the piezoelectric layer and the exposed vibration support layer area, such as Figure 3E As shown;

[0085] As can be seen, due to the pre-patterning of the piezoelectric layer, the upper portion of the upper electrode layer is formed above the piezoelectric layer, while its lower portion is formed directly above the vibration support layer, extending in the second direction outward from the vibration support layer and offset from the lower electrode layer. Its central portion is located lateral to the piezoelectric layer and is separated from the lower electrode layer by the piezoelectric layer.

[0086] Sub-step D5, depositing an electrode thickening layer on the lower electrode layer and the upper electrode layer, and patterning the electrode thickening layer to obtain a lower electrode thickening layer electrically connected to the lower electrode layer and an upper electrode thickening layer electrically connected to the upper electrode layer, such as Figure 3F shown.

[0087] In this step, the piezoelectric layer has a thickness between 0.1 μm and 10 μm, and its material is selected from one or more of the following: aluminum nitride, scandium-doped aluminum nitride, zinc oxide, and lead zirconate titanate. The top and bottom electrode layers have a thickness between 20 nm and 200 nm, and their materials are selected from one or more of the following: molybdenum, gold, aluminum, and chromium.

[0088] Step E: Deeply etch the inner side of the back side of the substrate until the vibration support layer is formed to form a substrate back cavity. Figure 3G shown.

[0089] In this step, the horizontal plane projection of the substrate back cavity is a circle with a radius of R.

[0090] In step F, the sacrificial layer below the vibration support layer is removed, so that the lower surface of the vibration support layer shows a thickness variation, that is, it is thick at the edge of the piezoelectric composite layer and thin in other areas, thereby increasing the vibration displacement of the entire vibration support layer while increasing the stability of the vibration support layer. Figure 3H shown.

[0091] In this embodiment, a vibration support layer showing thickness variation is prepared by using a sacrificial layer, which is lower in cost and easier to implement than other methods in the prior art.

[0092] It should be noted that the MEMS structure described above can be applied in any practical scenario to release residual stress in the composite vibration layer to improve performance. This application includes, but is not limited to, microphones, ultrasonic transducers, pressure sensors, or other actuators. Among these, MEMS piezoelectric microphones are a typical example. The following description will use a MEMS piezoelectric microphone as an example.

[0093] According to a third aspect of the present invention, based on the aforementioned MEMS structure, a MEMS piezoelectric microphone is provided. The microphone comprises the aforementioned MEMS structure, wherein an upper electrode layer and a lower electrode layer are connected to the output terminal of the MEMS piezoelectric microphone. The vibration support layer senses sound waves, driving the piezoelectric composite layer to vibrate. The piezoelectric layer senses strain, generating an electrical signal that is output through the upper and lower electrode layers.

[0094] Thus, the various embodiments of the present invention have been introduced. According to the above description, those skilled in the art should have a clear understanding of the present invention.

[0095] It should be noted that directional terms such as "upper," "lower," "front," "back," "left," "right," "inner," and "outer" mentioned in the embodiments are merely references to the directions in the accompanying drawings and are not intended to limit the scope of protection of the present invention. Throughout the drawings, identical elements are represented by identical or similar reference numerals. Furthermore, the shapes and dimensions of the components in the drawings do not reflect actual size or proportion but are merely illustrative of the contents of the embodiments of the present invention.

[0096] In addition, unless expressly indicated to the contrary, the numerical parameters in the specification and claims of the present invention may be approximate and may vary according to the content of the present invention. Specifically, all numbers indicating composition amounts, reaction conditions, etc. recorded in the specification and claims should be understood to be modified by the term "about" in all cases, and the meaning of the expression is to include a variation of ±10% from the specified quantity in some embodiments.

[0097] Those skilled in the art will understand that, in the claims and description of the present invention, the word "comprising" does not exclude the presence of elements (or steps) not listed in the claims. The word "a" or "an" preceding an element (or step) does not exclude the presence of a plurality of such elements (or steps).

[0098] For certain implementations, if they are not essential to the present invention and are well known to those skilled in the art, they are not described in detail in the drawings or the text of the specification due to space limitations. In such cases, reference should be made to the relevant prior art for understanding. Furthermore, the above embodiments are provided solely to ensure that the present invention meets legal requirements, and the present invention can be implemented in many different forms and should not be construed as limited to the embodiments described herein. Furthermore, the definitions of the various elements and methods described above are not limited to the specific structures, shapes, or methods described in the embodiments, and those skilled in the art may easily modify or replace them.

[0099] Similarly, it should be understood that in order to streamline the present invention, in the above description of the exemplary embodiments of the present invention, the various features of the present invention are sometimes grouped together into a single embodiment, figure, or description thereof. However, the method of the invention should not be interpreted as reflecting the intention that the claimed invention requires more features than those explicitly stated in each claim. More precisely, as reflected in the claims, each inventive aspect consists in less than all the features of the preceding single embodiment. Moreover, the embodiments can be mixed and matched with each other or with other embodiments based on design and reliability considerations, that is, the technical features in different embodiments can be freely combined to form more embodiments. Therefore, the claims following the specific embodiment are hereby expressly incorporated into the specific embodiment, with each claim itself serving as a separate embodiment of the present invention.

[0100] The above specific embodiments provide a detailed description of the objectives, technical means and beneficial effects of the present invention. It should be understood that the purpose of the detailed description is to enable those skilled in the art to understand the present invention more clearly, and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A MEMS structure, characterized in that: include: The substrate comprises: a peripheral substrate outer ring body; a substrate back cavity formed inside the substrate outer ring body; a vibration support layer formed above the substrate outer ring body and the substrate back cavity; A piezoelectric composite layer comprising: a lower electrode layer, a piezoelectric layer, and an upper electrode layer, which are sequentially formed above the vibration support layer, and a horizontal projection of the piezoelectric layer is located in the middle area of ​​a horizontal projection of the substrate back cavity; Wherein, in the horizontal direction, the vibration support layer includes: a connection stabilization area and a vibration reinforcement area, wherein the connection stabilization area is the area of ​​the vibration support layer corresponding to the edge position of the piezoelectric layer; the vibration reinforcement area is the area of ​​the vibration support layer away from the edge position of the piezoelectric layer; Among them, on the side away from the substrate back cavity, the vibration support layer is flat as a whole; on the side close to the substrate back cavity, the connection stabilization area protrudes downward in a ring shape, and its thickness H1 is greater than the thickness H2 of the vibration reinforcement area.

2. The MEMS structure according to claim 1, wherein: The lower electrode layer is formed directly above the vibration support layer and extends in a first direction toward the outside of the vibration support layer; The longitudinal section of the upper electrode layer is in a "Z" shape or a left-right mirrored "Z" shape, wherein the upper portion is formed above the piezoelectric layer, and the lower portion is formed directly above the vibration support layer, extending in a second direction toward the outside of the vibration support layer, and staggered with the lower electrode layer; The horizontal plane projection of the lower electrode layer portion below the piezoelectric layer at least partially overlaps with the horizontal plane projection of the upper electrode layer portion above the piezoelectric layer.

3. A MEMS piezoelectric microphone, characterized in that: include: The MEMS structure according to claim 1 or 2, wherein the upper electrode layer and the lower electrode layer are connected to an output terminal of the MEMS piezoelectric microphone; The vibration support layer senses sound waves to drive the piezoelectric composite layer to vibrate; the piezoelectric layer senses strain to generate electrical signals, which are output to the outside through the upper electrode layer and the lower electrode layer.

4. A method for preparing a MEMS structure according to claim 1 or 2, characterized in that: include: Step A, depositing a sacrificial layer on a substrate; Step B, patterning the sacrificial layer to form an annular groove at a location of a preset connection stabilization area; Step C, depositing a vibration support layer on the sacrificial layer having the annular groove, and planarizing the upper surface thereof; wherein the vibration support layer corresponding to the annular groove forms the connection stabilization area; and the vibration support layer corresponding to the non-annular groove portion forms the vibration reinforcement area; Step D, forming a lower electrode layer, a piezoelectric layer, and an upper electrode layer in sequence on the vibration support layer after the upper surface is planarized; Step E: deeply etching the inner side of the back surface of the substrate to the vibration support layer to form a substrate back cavity; Step F, removing the sacrificial layer below the vibration support layer.

5. The preparation method according to claim 4, characterized in that The step D comprises: Sub-step D1, depositing a lower electrode layer on the vibration support layer after the upper surface is planarized; Sub-step D2, patterning the lower electrode layer so that it covers a predetermined area of ​​the piezoelectric layer and extends in a first direction toward the outside of the vibration support layer, exposing an area of ​​the vibration support layer extending in a second direction toward the outside of the vibration support layer; Sub-step D3, depositing a piezoelectric layer on the lower electrode layer, and retaining only the piezoelectric layer in a predetermined area by patterning; Sub-step D4, depositing an upper electrode layer on the piezoelectric layer and the exposed vibration support layer area.

6. The preparation method according to claim 5, characterized in that Sub-step D4 further includes: Sub-step D5, depositing an electrode thickening layer on the lower electrode layer and the upper electrode layer, and patterning the electrode thickening layer to obtain a lower electrode thickening layer electrically connected to the lower electrode layer and an upper electrode thickening layer electrically connected to the upper electrode layer.

7. The preparation method according to claim 4, characterized in that In the step E, the horizontal plane projection of the substrate back cavity is a circle with a radius of R; In the step C, for the vibration support layer, the thickness of the connection stabilization area and the vibration reinforcement area satisfies: 1 / 3H1≤H2<H1; the annular ring width L1 of the connection stabilization area satisfies: 1 / 10R≤L1≤1 / 4R.

8. The preparation method according to claim 7, characterized in that For the vibration support layer, 300nm≤H1≤2000nm; 100nm≤L1≤500nm.

9. The preparation method according to claim 7, characterized in that For the piezoelectric layer, its horizontal plane projection is a circle with a radius R1 that satisfies:

10. The preparation method according to any one of claims 4 to 9, characterized in that The longitudinal section of the connection stabilization zone is a rectangle or an inverted isosceles triangle; and / or The substrate is one of the following: silicon wafer, SOI substrate, polysilicon on SiO2 / Si; and / or The vibration support layer is a single-layer film or a multi-layer film, and its material is one or more of the following: silicon nitride, silicon oxide, single crystal silicon, polycrystalline silicon; and / or The thickness of the piezoelectric layer is between 0.1 μm and 10 μm, and the material thereof is selected from one or more of the following: aluminum nitride, scandium-doped aluminum nitride, zinc oxide, lead zirconate titanate; and / or The thickness of the upper electrode layer and the lower electrode layer is between 20 nm and 200 nm, and the materials thereof are selected from one or more of the following: molybdenum, gold, aluminum, and chromium.

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