Piezoelectric microphone and manufacturing method therefor, electronic device and sound source detection method

Abstract

Embodiments of the present application provide a piezoelectric microphone and a manufacturing method therefor, an electronic device and a sound source detection method. The piezoelectric microphone comprises: a substrate provided with a back hole; and a structural layer connected to the substrate and covering one side of the back hole, wherein the structural layer comprises a main body and a cantilever beam, and a gap exists between the cantilever beam and the main body; a piezoelectric layer is arranged on the cantilever beam, and a first electrode and a second electrode are arranged on two sides of the piezoelectric layer, respectively. The embodiments of the present application have the advantages of simple structure and low cost.

Description

Piezoelectric microphone, manufacturing method thereof, electronic device, and sound source detection method

[0001] This application claims priority to the Chinese patent application filed with the China Patent Office on December 15, 2023, with application number 202311734821.3, and entitled “Piezoelectric microphone and its manufacturing method, electronic device, and sound source detection method,” the entire contents of which are incorporated herein by reference. Technical Field

[0002] The present application belongs to the field of acoustic technology. Specifically, the present application relates to a piezoelectric microphone and a manufacturing method thereof, an electronic device, and a sound source detection method. Background Art

[0003] Piezoelectric microphones convert the vibrations of a diaphragm into electrical signals by placing a piezoelectric layer on top of the diaphragm. However, further improving the signal-to-noise ratio of existing piezoelectric microphones often requires complex structural designs and high manufacturing costs. Summary of the Invention

[0004] One purpose of the embodiments of the present application is to provide a new technical solution for a piezoelectric microphone, a manufacturing method thereof, and a sound source detection method.

[0005] According to a first aspect of an embodiment of the present application, a piezoelectric microphone is provided, comprising: a substrate provided with a back hole; a structural layer connected to the substrate and covering one side of the back hole, the structural layer comprising a main body and a cantilever beam, with a gap between the cantilever beam and the main body; the cantilever beam being provided with a piezoelectric layer, and a first electrode and a second electrode being respectively provided on both sides of the piezoelectric layer.

[0006] Optionally, the cantilever beam includes a root portion and a leaf portion, the root portion is connected to the leaf portion, and a width of the root portion is smaller than a width of the leaf portion.

[0007] Optionally, the length of the root portion is shorter than the length of the leaf portion.

[0008] Optionally, the piezoelectric layer is at least partially located at the root.

[0009] Optionally, there is an arc transition between the root and the leaf.

[0010] Optionally, an orthographic projection of the cantilever beam toward the substrate is located in the back hole.

[0011] Optionally, the root is provided with texture.

[0012] Optionally, the structural layer includes a plurality of cantilever beams, the plurality of cantilever beams are arranged radially, and roots of the plurality of cantilever beams are close to each other.

[0013] Optionally, the first electrodes on the plurality of cantilever beams are connected to each other, or the second electrodes on the plurality of cantilever beams are connected to each other.

[0014] Optionally, a sacrificial layer is further provided between the structural layer and the substrate.

[0015] According to a second aspect of the embodiments of the present application, an electronic device is further provided, comprising the piezoelectric microphone as described above.

[0016] According to a third aspect of an embodiment of the present application, a method for manufacturing a piezoelectric microphone is also provided, comprising: arranging a piezoelectric layer on a structural layer, wherein a first electrode and a second electrode are arranged on both sides of the piezoelectric layer; processing a gap on the structural layer to form a cantilever beam, so that the piezoelectric layer is located on the cantilever beam.

[0017] Optionally, the manufacturing method of the piezoelectric microphone further includes: disposing the structural layer on a substrate and disposing a sacrificial layer between the substrate and the structural layer; machining a back hole on the substrate; and corroding the sacrificial layer so that the structural layer is located on one side of the back hole.

[0018] Optionally, gaps are machined on the structural layer to form a plurality of cantilever beams, each of which includes a root and a leaf, and the plurality of cantilever beams are arranged radially, with the roots of the plurality of cantilever beams close to each other.

[0019] According to a fourth aspect of an embodiment of the present application, a method for sound source detection using a piezoelectric microphone as described above is also provided, comprising: obtaining voltage signals output by at least four cantilever beams; performing X-direction differential and Y-direction differential on the voltage signals; and comparing the X-direction differential results with the Y-direction differential results to determine the position of the sound source.

[0020] Optionally, the sound source detection method further includes: calculating a difference between an X-direction differential result and a Y-direction differential result; calculating a ratio between the difference and the X-direction differential result or the Y-direction differential result, and determining the angle of the sound source according to the ratio.

[0021] One technical effect of the present application is that a cantilever beam is directly processed on a structural layer, which can improve the signal-to-noise ratio of the piezoelectric microphone with a simple structure and low manufacturing cost, and has high sensitivity.

[0022] Other features and advantages of the present application will become apparent from the following detailed description of exemplary embodiments of the present application with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the application and, together with the description, serve to explain the principles of the application.

[0024] FIG1 is an exploded view of a piezoelectric microphone provided in a first embodiment of the present application;

[0025] FIG2 is a top view of the structural layer provided in the first embodiment of the present application;

[0026] FIG3 is a top view of a piezoelectric microphone provided in the first embodiment of the present application;

[0027] FIG4 is a cross-sectional view along line AA in FIG3 ;

[0028] FIG5 is an exploded view of a piezoelectric microphone provided in a second embodiment of the present application;

[0029] FIG6 is a top view of a piezoelectric microphone provided in a second embodiment of the present application;

[0030] FIG7 is a cross-sectional view along line BB in FIG6;

[0031] FIG8 is a schematic diagram of a sound source detection method according to an embodiment of the present application;

[0032] FIG9 is a top view of a structural layer provided in a third embodiment of the present application;

[0033] FIG10 is a top view of the structural layer provided in the fourth embodiment of the present application.

[0034] Explanation of the accompanying drawings: 1. Base; 11. Back hole; 2. Structural layer; 21. Main body; 22. Cantilever beam; 221. Root; 222. Leaf; 23. Gap; 3. Piezoelectric layer; 4. First electrode; 5. Second electrode; 6. Sacrificial layer; 7. Sound source. DETAILED DESCRIPTION

[0035] Various exemplary embodiments of the present application will now be described in detail with reference to the accompanying drawings. It should be noted that unless otherwise specifically stated, the relative arrangements of components and steps, numerical expressions and numerical values ​​set forth in these embodiments do not limit the scope of the present application.

[0036] The embodiments of the present application will be described in detail below, and examples of the embodiments are shown in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present application, and should not be understood as limiting the present application. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of this application.

[0037] The terms "first" and "second" in the specification and claims of this application may explicitly or implicitly refer to one or more of the features. Throughout the description of this application, unless otherwise specified, "plurality" means two or more. Furthermore, "and / or" in the specification and claims refers to at least one of the connected entities, and the character " / " generally indicates an "or" relationship between the connected entities.

[0038] In the description of the present application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0039] In the description of this application, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; and internal connections between two components. Those skilled in the art will understand the specific meanings of the above terms in this application based on the specific circumstances.

[0040] It should be noted that like reference numerals and letters refer to like items in the following figures, and therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0041] As shown in FIG1 , the piezoelectric microphone in this embodiment includes: a substrate 1, a structural layer 2, and a piezoelectric layer 3. The substrate 1 can be made of commonly used materials for MEMS (Micro-Electro-Mechanical System) sensors, such as silicon-based materials. The substrate 1 is provided with a back hole 11, which can be regarded as a through hole formed on the substrate 1, and its main function is to pick up vibrations and provide a vibration space for the cantilever beam 22. The back hole 11 can be circular or square, or any other shape. The structural layer 2 can be made of commonly used diaphragm materials such as polycrystalline silicon, and its main function is to vibrate along with the vibration of an external medium such as air. The piezoelectric layer 3 can be made of piezoelectric materials such as aluminum nitride, and its main function is to convert the vibration of the cantilever beam 22 into an electrical signal.

[0042] As shown in Figures 1 and 4 , the structural layer 2 is connected to the substrate 1 and covers one side of the back hole 11. More specifically, in Figures 1 and 4 , the structural layer 2 covers the upper side of the back hole 11. Although a gap 23 exists in the structural layer 2, the structural layer 2 is still considered to cover one side of the back hole 11. Therefore, the term "covering" does not mean "sealing" in this article. The width of the gap 23 can be designed as needed.

[0043] As shown in Figures 1 to 4, the structural layer 2 includes a main body 21 and a cantilever beam 22. A gap 23 exists between the cantilever beam 22 and the main body 21. In other words, the gap 23 is machined into the main body 21, thereby forming the cantilever beam 22. The cantilever beam 22 and the main body 21 remain connected. The cantilever beam 22 is provided with a piezoelectric layer 3. As shown in Figure 4, the piezoelectric layer 3 is provided with a first electrode 4 and a second electrode 5 on its upper and lower sides, respectively.

[0044] When an external medium, such as air, vibrates, cantilever beam 22 generates strain, and thus piezoelectric layer 3 on cantilever beam 22 also generates strain. The charges generated on the upper and lower sides of piezoelectric layer 3 are collected by first electrode 4 and second electrode 5, realizing vibration signal sensing. Because the cantilever beam 22 is directly machined on structural layer 2, the present application has a simple structure, low manufacturing cost, and high sensitivity.

[0045] As shown in Figure 2, the cantilever beam 22 in this embodiment includes a root portion 221 and a leaf portion 222, with the root portion 221 connected to the leaf portion 222. The width W1 of the root portion 221 is smaller than the width W2 of the leaf portion 222. In other words, the leaf portion 222 is formed by expanding the distal end of the root portion 221. The advantage of this structure is that, because the leaf portion 222 has a greater width, it can increase the strain of the root portion 221, thereby increasing the sensitivity to vibration signals.

[0046] As shown in Figure 2, the length L1 of the root 221 is smaller than the length L2 of the blade 222, so the cantilever beam 22 forms a paddle shape. The advantage of this structure is that the longer blade 222 can increase the strain of the root 221, thereby increasing the sensitivity to vibration signals.

[0047] As shown in FIG3 , the piezoelectric layer 3 is at least partially or entirely located at the root 221. Since the cantilever beam 22 has the paddle shape described above, the blade 222 has a larger width and / or length. Therefore, the strain at the root 221 of the cantilever beam 22 is the greatest. Partially disposing the piezoelectric layer 3 at the root 221 can improve the sensitivity of the piezoelectric microphone.

[0048] As shown in Figure 3, the root 221 and the leaf 222 are connected by an arc transition, which can avoid stress concentration. Similarly, the edge of the leaf 222 can also be connected by an arc transition to avoid stress concentration.

[0049] As shown in Figures 3 and 4 , the orthographic projection of the cantilever beam 22 (including the root portion 221 and the leaf portion 222) toward the substrate 1 is located within the back hole 11. This configuration has the advantage of allowing the cantilever beam 22 to generate sufficient strain, thereby ensuring that the piezoelectric layer 3 generates sufficient strain, thereby increasing the sensitivity of the piezoelectric microphone.

[0050] In the embodiment of the present application, the root portion 221 may also be provided with textures (not shown) to make the root portion 221 more susceptible to strain, thereby improving the sensitivity of the piezoelectric microphone.

[0051] The sensitivity of the piezoelectric microphone can be controlled by changing the shape and thickness of the cantilever beam 22 or by changing the thickness and area of ​​the piezoelectric layer 3 .

[0052] In the embodiments shown in Figures 1 to 4, the structural layer 2 and the cantilever beam 22 are single-layer structures. In practical applications, the number of layers can be increased to form a multi-layer structure. Similarly, the number of layers of the piezoelectric layer 3 can also be multi-layered, in which case the number of electrodes needs to be increased accordingly.

[0053] As shown in Figures 5 to 7 , in a second embodiment of the present application, a structural layer 2 includes multiple cantilever beams 22, with Figure 6 showing four cantilever beams 22. The cantilever beams 22 are arranged radially, with their bases 221 close to each other. Each cantilever beam 22 is provided with a piezoelectric layer 3, and each piezoelectric layer 3 is provided with a first electrode 4 and a second electrode 5 on either side.

[0054] More specifically, the four cantilever beams 22 shown in FIG6 are arranged in a cross shape, with the roots 221 of the four cantilever beams 22 closer to a center O of the structural layer 2, and the four cantilever beams 22 are arranged radially around the center O. This structure allows for the use of a single piezoelectric microphone to achieve sound source localization, which is more cost-effective and will be described in detail below.

[0055] As shown in Figure 7, the second electrodes 5 on the multiple cantilever beams 22 are interconnected and maintain the same potential, which can serve as a common ground terminal, simplifying manufacturing. Alternatively, the first electrodes 4 on the multiple cantilever beams 22 are interconnected and maintain the same potential, which can serve as a common ground terminal, simplifying manufacturing. Because the four roots 221 are close to each other, and the piezoelectric layer 3 can be at least partially located at the roots 221, the first electrodes 4 and second electrodes 5 can be close to each other. When connection is required, the same electrode can be used for manufacturing, achieving higher sensitivity while saving material costs and simplifying manufacturing.

[0056] As shown in FIG. 4 and FIG. 7 , a sacrificial layer 6 is further provided between the structural layer 2 and the substrate 1 . The sacrificial layer 6 can protect the structural layer 2 during the manufacturing process of the piezoelectric microphone.

[0057] As shown in FIG9 , in the third embodiment of the present application, five cantilever beams 22 are machined on one structural layer 2. As shown in FIG10 , in the fourth embodiment of the present application, six cantilever beams 22 are machined on one structural layer 2. Therefore, the number of cantilever beams 22 can be increased or decreased as needed. When there are multiple (at least two) cantilever beams 22, the multiple cantilever beams 22 are arranged radially.

[0058] An embodiment of the present application further provides an electronic device that uses the piezoelectric microphone as described above, and thus has the advantages of simple structure, low cost, and higher sensitivity to sound sources.

[0059] The embodiments of the present application also provide a method for manufacturing a piezoelectric microphone, which is used to manufacture the piezoelectric microphone described above. The method includes: providing a piezoelectric layer 3 on a structural layer 2, with a first electrode 4 and a second electrode 5 provided on both sides of the piezoelectric layer 3; processing a gap 23 on the structural layer 2 to form a cantilever beam 22, so that the piezoelectric layer 3 is located on the cantilever beam 22. The gap 23 can be processed by common chip processing methods such as photolithography. Compared with the prior art of using dual diaphragms or dual back poles to improve the signal-to-noise ratio of piezoelectric microphones, the manufacturing method of the embodiment of the present application is simpler and less expensive. However, the present application does not exclude the use of multiple structural layers 2 and multiple cantilever beams 22 to further improve sensitivity.

[0060] The piezoelectric microphone manufacturing method of this embodiment further includes: disposing a structural layer 2 on a substrate 1, and disposing a sacrificial layer 6 between the substrate 1 and the structural layer 2; machining a back hole 11 in the substrate 1; and etching the sacrificial layer 6 so that the structural layer 2 is located on one side of the back hole 11. While machining the back hole 11 in the substrate 1, the sacrificial layer 6 protects the structural layer 2 and the cantilever beam 22 from damage. After machining the back hole 11, the sacrificial layer 6 is further etched so that the structural layer 2 is located on one side of the back hole 11.

[0061] In the piezoelectric microphone manufacturing method of the embodiment of the present application, when machining gaps 23 in the structural layer 2, multiple cantilever beams 22 are formed. Each cantilever beam 22 includes a root portion 221 and a leaf portion 222. The multiple cantilever beams 22 are arranged radially, with the roots 221 of the multiple cantilever beams 22 being close to each other. This results in a multi-cantilever beam 22 structure as shown in Figures 5 to 10.

[0062] As shown in FIG8 , four cantilever beams 22 are used as an example to illustrate the sound source detection method using the aforementioned piezoelectric microphone.

[0063] Assuming that the position of the sound source 7 is as shown in FIG8 , after the sound source 7 makes a sound, the vibration will be sensed by the four cantilever beams 22 , so the voltage signals output by the piezoelectric layers 3 of the four cantilever beams 22 are obtained as X1 , X2 , Y1 and Y2 , respectively.

[0064] Next, the voltage signal is differentiated in the X direction and the Y direction. More specifically, the X-direction differential is: ΔX=X1-X2, and the Y-direction differential is: ΔY=Y1-Y2.

[0065] The X- and Y-axis differential results are then compared to determine the location of sound source 7. In this embodiment, since sound source 7 is closer to the right cantilever beam 22 in the X direction, the voltage signal X1 of the right cantilever beam 22 is larger than the voltage signal X2 of the left cantilever beam 22. Therefore, ΔX = X1 - X2 > 0, indicating that sound source 7 is closer to the right in the X direction. Similarly, ΔY = Y1 - Y2 > 0, indicating that sound source 7 is closer to the top in the Y direction. Therefore, the location of sound source 7 is in the upper right, and its specific coordinates can be represented by ΔX and ΔY.

[0066] In the prior art, a single condenser microphone lacks directivity, and using a dual-core microphone for sound source localization is costly. However, the embodiment of the present application uses multiple cantilever beams 22 of a single piezoelectric microphone to achieve sound source 7 localization detection at a lower cost.

[0067] As shown in FIG8 , the sound source detection method in this embodiment further includes calculating the difference ΔX-ΔY between the X-direction differential result and the Y-direction differential result; calculating the ratio (ΔX-ΔY) / ΔX between the difference and the X-direction differential result, and determining the angle of sound source 7 based on the ratio. More specifically, the closer (ΔX-ΔY) / ΔX is to 1, the smaller the angle between sound source 7 and the X-direction; the closer (ΔX-ΔY) / ΔX is to 0, the closer the angle between sound source 7 and the X-direction is to 45°. Similarly, the ratio (ΔX-ΔY) / ΔY between the difference and the Y-direction differential result can also be calculated, and the angle of sound source 7 can be determined based on the ratio. The closer (ΔX-ΔY) / ΔY is to -1, the smaller the angle between sound source 7 and the Y-direction; the closer (ΔX-ΔY) / ΔY is to 0, the closer the angle between sound source 7 and the Y-direction is to 45°. In this way, the position and angle of the sound source 7 can be detected through the four cantilever beams 22 of a piezoelectric microphone, and the cost is low.

[0068] The above method is also applicable to the scenario of multiple cantilever beams 22 as shown in Figures 9 and 10. The more cantilever beams 22 there are, the more accurate the detection result of the sound source 7 will be.

[0069] Although some specific embodiments of the present application have been described in detail by way of examples, it should be understood by those skilled in the art that the above examples are for illustration only and are not intended to limit the scope of the present application. It should be understood by those skilled in the art that the above embodiments may be modified without departing from the scope and spirit of the present application. The scope of the present application is defined by the appended claims.

Claims

1. A piezoelectric microphone, characterized in that: include: A substrate, wherein the substrate is provided with a back hole; a structural layer, the structural layer being connected to the substrate and covering one side of the back hole, the structural layer comprising a main body and a cantilever beam, and a gap being present between the cantilever beam and the main body; The cantilever beam is provided with a piezoelectric layer, and a first electrode and a second electrode are respectively provided on both sides of the piezoelectric layer.

2. The piezoelectric microphone according to claim 1, characterized in that The cantilever beam comprises a root portion and a leaf portion, wherein the root portion is connected to the leaf portion, and a width of the root portion is smaller than a width of the leaf portion.

3. The piezoelectric microphone according to claim 2, characterized in that: The length of the root portion is shorter than the length of the leaf portion.

4. The piezoelectric microphone according to claim 2 or 3, characterized in that: The piezoelectric layer is at least partially located at the root.

5. The piezoelectric microphone according to claim 2 or 3, characterized in that: There is an arc transition between the root and the leaf.

6. The piezoelectric microphone according to claim 1, characterized in that: The orthographic projection of the cantilever beam toward the substrate is located in the back hole.

7. The piezoelectric microphone according to claim 2 or 3, characterized in that: The root is provided with textures.

8. The piezoelectric microphone according to claim 2 or 3, characterized in that: The structural layer includes a plurality of cantilever beams, the plurality of cantilever beams are arranged radially, and the roots of the plurality of cantilever beams are close to each other.

9. The piezoelectric microphone according to claim 8, characterized in that: The first electrodes on the multiple cantilever beams are connected to each other, or the second electrodes on the multiple cantilever beams are connected to each other.

10. The piezoelectric microphone according to claim 1, wherein: A sacrificial layer is also arranged between the structural layer and the substrate.

11. An electronic device, characterized in that: The electronic device comprises the piezoelectric microphone according to any one of claims 1 to 10.

12. A method for manufacturing a piezoelectric microphone, characterized in that: include: A piezoelectric layer is arranged on the structural layer, and a first electrode and a second electrode are arranged on both sides of the piezoelectric layer; A gap is processed on the structural layer to form a cantilever beam, and the piezoelectric layer is located on the cantilever beam.

13. The method for manufacturing a piezoelectric microphone according to claim 12, characterized in that: Also includes: Disposing the structural layer on a substrate, and disposing a sacrificial layer between the substrate and the structural layer; machining a back hole on the substrate; The sacrificial layer is corroded so that the structural layer is located at one side of the back hole.

14. The method for manufacturing a piezoelectric microphone according to claim 12, wherein: Gaps are machined on the structural layer to form a plurality of cantilever beams, each of which includes a root and a leaf. The plurality of cantilever beams are arranged radially, and the roots of the plurality of cantilever beams are close to each other.

15. A method for detecting a sound source using the piezoelectric microphone according to any one of claims 1 to 10, characterized in that: include: Acquire voltage signals output by at least four cantilever beams; Performing X-direction differentiation and Y-direction differentiation on the voltage signal; Compare the X- and Y-direction differential results to determine the location of the sound source.

16. The sound source detection method according to claim 15, characterized in that: Also includes: Calculate the difference between the X-direction differential result and the Y-direction differential result; A ratio between the difference and the X-direction difference result or the Y-direction difference result is calculated, and the angle of the sound source is determined according to the ratio.

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