A MEMS microphone structure

Abstract

The present invention provides a MEMS microphone structure comprising a diaphragm, a backplate, a central acoustic hole, and a plurality of peripheral acoustic holes. The backplate is located above the diaphragm and vertically spaced apart from the backplate by a predetermined distance to form an air gap. At least a portion of the backplate is connected to the upper surface of the backplate to support the backplate. The central acoustic hole is located at the center of the backplate and vertically extends through the backplate and the backplate. The plurality of peripheral acoustic holes are distributed around the central acoustic hole in a concentric circle arrangement with the central acoustic hole as the center, with the edge of the backplate not passing through any of the peripheral acoustic holes. The present invention optimizes the arrangement and distribution of the acoustic holes, making it easier to control the edge of the backplate to be located between two concentric circles of peripheral acoustic holes, rather than intersecting the portion of the backplate with the acoustic holes. This effectively reduces stress concentration at the interface between the backplate edge and the backplate, preventing cracks and damage in the portion susceptible to stress concentration, thereby improving the mechanical reliability of the MEMS microphone.

Description

Technical Field

[0001] The invention belongs to the technical field of microphones and relates to a MEMS microphone structure. Background Art

[0002] Today's smartphones and smart speakers all use microphones manufactured using MEMS (Micro-Electro-Mechanical System) technology. This type of microphone features small size, low power consumption, excellent performance, good consistency, and easy assembly. The MEMS microphone structure includes an insulating backplate structure that supports the back electrode. To allow external sound waves to reach the diaphragm, corresponding sound holes are opened on the back electrode and backplate. However, stress concentration occurs at the junction of the back electrode edge and the sound hole on the backplate. To reduce this effect, requirements are put forward for the design of the sound hole arrangement. Summary of the Invention

[0003] In view of the above-mentioned shortcomings of the prior art, the present invention aims to provide a MEMS microphone structure to solve the problem in the prior art that the junction between the back pole and the back plate of the MEMS microphone is easily affected by stress concentration and cracks are generated, resulting in device damage.

[0004] To achieve the above-mentioned and other related objectives, the present invention provides a MEMS microphone structure, comprising:

[0005] diaphragm;

[0006] a back pole, located above the diaphragm and spaced apart from the back pole by a preset distance in a vertical direction to form an air gap;

[0007] a back plate, at least a portion of which is connected to the upper surface of the back electrode to support the back electrode;

[0008] a central acoustic hole located at the center of the back pole and penetrating the back pole and the back plate in a vertical direction;

[0009] A plurality of peripheral sound holes are distributed around the central sound hole and are arranged in concentric circles with the central sound hole as the center. The edge of the back pole does not pass through any of the peripheral sound holes.

[0010] Optionally, the projection of at least one of the peripheral sound holes on the horizontal plane is located in the area where the back pole is located, and passes through the back pole and the back plate in the vertical direction. The projection of at least one of the peripheral sound holes on the horizontal plane is located outside the area where the back pole is located, and passes through the back plate in the vertical direction.

[0011] Optionally, in the direction from the back pole center to the back pole edge, the number of the peripheral sound holes in the i-th circle is 6i, where i is an integer greater than 0.

[0012] Optionally, the 6i peripheral sound holes in the i-th circle are located on the 6i vertices of a regular 6i-gon.

[0013] Optionally, each circle of the peripheral sound holes has two peripheral sound holes located on a first straight line, and the first straight line passes through the center of the back pole.

[0014] Optionally, the central sound hole and the peripheral sound holes do not contact each other, any two adjacent peripheral sound holes do not contact each other, and in the direction from the back pole center to the back pole edge, the distance between the peripheral sound holes and the central sound hole located on the i-th circle is i times D, where i is an integer greater than 0.

[0015] Optionally, the edge profile of the back pole is circular.

[0016] Optionally, the edge of the back pole is located between the i-th circle of peripheral sound holes and the i+1-th circle of peripheral sound holes in the direction from the center of the back pole to the edge of the back pole, and the edge contour of the back pole is a regular 6i-gon or a regular 6(i+1)-gon, where i is an integer greater than 1.

[0017] Optionally, the opening shape of the peripheral sound hole is circular or regular polygonal.

[0018] Optionally, the MEMS microphone structure further includes:

[0019] a substrate, located below the diaphragm and supporting the back plate;

[0020] a cavity located in the substrate and penetrating the substrate in a vertical direction;

[0021] The bracket is located between the substrate and the diaphragm and is used to support the diaphragm.

[0022] Optionally, the MEMS microphone structure further includes a backpole lead electrode and a diaphragm lead electrode, the backpole lead electrode is arranged on the side of the backplate facing away from the diaphragm, and penetrates the backplate to be connected to the backpole, and the diaphragm lead electrode is located on the side of the backplate facing away from the diaphragm, and penetrates the backplate to be connected to the diaphragm.

[0023] Optionally, the MEMS microphone structure further includes a blocking block, which vertically penetrates the back pole and is connected to the back plate, and a distance between the blocking block and the diaphragm is smaller than a distance between the back pole and the diaphragm.

[0024] As described above, the MEMS microphone structure of the present invention optimizes the arrangement and distribution of the sound holes, and can more easily control the back pole edge to be located between two circles of concentrically distributed peripheral sound holes, without intersecting with the back plate portion with the sound holes, thereby effectively reducing the stress concentration at the junction of the back pole edge and the back plate, avoiding cracks and damage in the portion susceptible to stress concentration, thereby improving the mechanical reliability of the MEMS microphone. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 Shown is a cross-sectional view of the MEMS microphone structure of the present invention.

[0026] Figure 2 Shown is a schematic diagram of the arrangement of the acoustic holes of the MEMS microphone of the present invention.

[0027] Figure 3 Display as Figure 2 Schematic diagram of the backplane in area B.

[0028] Figure 4 Shown is a schematic diagram of a conventional sound hole arrangement.

[0029] Figure 5 Display as Figure 4 Schematic diagram of the backplane in area C.

[0030] Figure 6 It is shown as the result of the physical field modeling and simulation software COMSOL Figure 3 Stress simulation is performed on the block.

[0031] Figure 7 It is shown as the result of the physical field modeling and simulation software COMSOL Figure 5 Stress simulation is performed on the block.

[0032] Component number description

[0033] 1 diaphragm

[0034] 2, 2' Dorsal Pole

[0035] 3. 3' backboard

[0036] 4 center sound hole

[0037] 5 peripheral sound holes

[0038] 5' sound hole

[0039] 6 Air Gap

[0040] 7 Back electrode lead-out electrode

[0041] 8 Diaphragm lead-out electrode

[0042] 9 substrate

[0043] 10 Cavity

[0044] 11 Bracket

[0045] 12 Blocks

[0046] 13 Diaphragm stopper

[0047] 14 vent holes

[0048] 15 Insulation layer

[0049] 16 External bracket

[0050] 17 Annular slit

[0051] L First straight line

[0052] Areas A, B, and C

[0053] S The boundary between the back pole and the back plate DETAILED DESCRIPTION

[0054] The following describes the embodiments of the present invention through specific examples. Those skilled in the art will readily understand the other advantages and benefits of the present invention from the disclosure herein. The present invention may also be implemented or applied through various other specific embodiments, and the details in this specification may be modified or altered based on different viewpoints and applications without departing from the spirit of the present invention.

[0055] See also Figures 1 to 7 It should be noted that the diagrams provided in this embodiment are merely schematic illustrations of the basic concept of the present invention. Therefore, the diagrams only show components related to the present invention and are not drawn according to the number, shape, and size of components in actual implementation. In actual implementation, the type, quantity, and proportion of each component may be changed arbitrarily, and the component layout may also be more complex.

[0056] This embodiment provides a MEMS microphone structure. Figure 1 , which shows a cross-sectional view of the MEMS microphone structure, including a diaphragm 1, a backpole 2, a backplate 3, a central sound hole 4 and a plurality of peripheral sound holes 5, wherein the backpole 2 is located above the diaphragm 1 and is spaced a preset distance from the backpole 2 in the vertical direction to form an air gap 6; at least a portion of the backplate 3 is connected to the upper surface of the backpole 2 to support the backpole 2; the central sound hole 4 is located at the center of the backpole 2 and penetrates the backpole 2 and the backplate 3 in the vertical direction; the plurality of peripheral sound holes 5 are distributed around the central sound hole 4 and are distributed in concentric circles with the central sound hole 4 as the center, and the edge of the backpole 2 does not pass through any of the peripheral sound holes 5.

[0057] As an example, the opening area of each acoustic hole in the back plate 3 is larger than the opening area in the back pole 2 .

[0058] As an example, the MEMS microphone structure further includes a backpole lead-out electrode 7 and a diaphragm lead-out electrode 8. The backpole lead-out electrode 7 is provided on the side of the backplate 3 facing away from the diaphragm 1 and penetrates the backplate 3 to connect with the backpole 2. The diaphragm lead-out electrode 8 is located on the side of the backplate 3 facing away from the diaphragm 1 and penetrates the backplate 3 to connect with the diaphragm 1. The backpole lead-out electrode 7 and the diaphragm lead-out electrode 8 are made of a conductive material, such as a conductive metal.

[0059] As an example, the projection of at least one of the peripheral sound holes on the horizontal plane is located in the area where the back pole 2 is located, and vertically passes through the back pole 2 and the back plate 3. The projection of at least one of the peripheral sound holes on the horizontal plane is located outside the area where the back pole 2 is located, and vertically passes through the back plate 3. It should be noted that Figure 1 The cross section shown passes through the back electrode lead electrode 7 and the diaphragm lead electrode 8. The cross section path does not pass through the peripheral sound holes outside the area where the back electrode 2 is located. Therefore, the peripheral sound holes outside the area where the back electrode 2 is located are not included in the cross section. Figure 1 Presented in.

[0060] As an example, see Figure 2 , which is a schematic diagram showing the arrangement of the acoustic holes of the MEMS microphone of the present invention, wherein, Figure 2 The figure also shows the periphery of the back plate 3 and the edge of the back pole 2. In this embodiment, in the direction from the center of the back pole 2 to the edge of the back pole 2, the number of the peripheral sound holes 5 in the i-th circle is 6i, where i is an integer greater than 0. For example, Figure 2 The figure shows six concentric circles of peripheral sound holes 5. The first circle contains 6 peripheral sound holes, the second circle contains 12 peripheral sound holes, the third circle contains 18 peripheral sound holes, the fourth circle contains 24 peripheral sound holes, the fifth circle contains 30 peripheral sound holes, and the sixth circle contains 36 peripheral sound holes. It should be noted that the number of peripheral sound holes can be adjusted according to the size of the back electrode and back plate, as well as the performance requirements of the microphone. This is only an example and should not unduly limit the scope of protection of the present invention.

[0061] As an example, the 6i peripheral sound holes 5 of the i-th circle are located at the 6i vertices of a regular 6i-gon. For example, the 6 peripheral sound holes of the first circle are located at the six vertices of a regular hexagon, the 12 peripheral sound holes of the second circle are located at the 12 vertices of a regular 12-gon, the 18 peripheral sound holes of the third circle are located at the 18 vertices of a regular 18-gon, the 24 peripheral sound holes of the fourth circle are located at the 24 vertices of a regular 24-gon, the 30 peripheral sound holes of the fifth circle are located at the 30 vertices of a regular 30-gon, and the 36 peripheral sound holes of the sixth circle are located at the 36 vertices of a regular 36-gon. The same applies to more circles of peripheral sound holes. Evenly distributed sound holes facilitate uniform transmission of sound waves.

[0062] As an example, each circle of peripheral sound holes has two peripheral sound holes located on a first straight line L that passes through the center of the back plate 2, resulting in the following arrangement: For example, using 1 / 6 of the back plate area as an example, starting with the central sound hole, the remaining sound holes are arranged outward along two sides of a 60° central angle. The second sound hole, as the vertex, is located on the bisector of the 60° central angle, and the remaining sound holes are then arranged along lines parallel to the two sides of the first 60° central angle, also with the second vertex.

[0063] As an example, the central sound hole and the peripheral sound holes do not touch each other, and any two adjacent peripheral sound holes do not touch each other. In the direction from the center of the back pole 2 to the edge of the back pole 2, the distance between the peripheral sound holes 5 and the central sound hole 4 located on the i-th circle is i times D, where i is an integer greater than 0. That is to say, the distance between two adjacent circles of peripheral sound holes is equal, and is equal to the distance between the first circle of peripheral sound holes and the central sound hole. For example, in the above description based on 1 / 6 of the back plate area, the distance between the second sound hole as the vertex and the central sound hole is equal to the distance between the third sound hole on the horizontal line of the central sound hole ( Figure 2 The distance from the third sound hole as the vertex to the center sound hole is equal to the distance from the fifth sound hole on the horizontal line of the center sound hole to the center, and the subsequent sound holes are arranged in this order.

[0064] As an example, the edge of the back pole 2 is located between the i-th circle of peripheral sound holes and the i+1-th circle of peripheral sound holes in the direction from the center of the back pole 2 to the edge of the back pole 2, wherein: Figure 2 The embodiment shows a case where the edge of the back pole 2 is located between the fifth and sixth circles of peripheral acoustic holes. In other embodiments, the number of circles of peripheral acoustic holes outside the area where the back pole 2 is located may be more than one, and this should not unduly limit the scope of protection of the present invention.

[0065] As an example, the edge profile of the back pole 2 can be a circle, a regular 6i-gon or a regular 6(i+1)-gon. Figure 2 In the illustrated embodiment, the edge profile of the back electrode 2 may be a circle, a regular 30-gon, or a regular 36-gon. In this embodiment, the edge profile of the back electrode 2 is preferably a circle.

[0066] Since the plurality of peripheral sound holes 5 are distributed around the central sound hole 4 and are distributed in concentric circles with the central sound hole 4 as the center, by arranging the sound holes in this manner, it is easier to control the edge of the back pole 2 to be located exactly between the two circles of concentrically arranged peripheral sound holes 5 without intersecting with the portion of the back plate 3 with the sound holes.

[0067] See also Figure 3 , displayed as Figure 2 The schematic diagram of the backplane in the middle area B (close to the bottom view), it should be noted that, Figure 2 Not drawn to scale. Figure 2 In the figure, the boundary line between the back pole and the back plate in area B is a relatively obvious arc line. However, in reality, although the boundary line between the back pole and the back plate is an arc line, it tends to be like Figure 3 In the design of the present invention, the boundary line S between the back pole and the back plate does not pass through the acoustic hole on the back plate 3.

[0068] For comparison, see Figure 4 , shows a schematic diagram of a conventional sound hole arrangement. In this arrangement, with any sound hole 5' as the center, it can form a regular hexagonal arrangement with the other 6 sound holes around it. When sound holes are arranged on the back plate 3' in this way, the edge of the back pole 2' will inevitably intersect with the area where the sound holes are opened on the back plate 3'. Figure 5 , displayed as Figure 4 Schematic diagram of the back plate 3' in the middle area C (close to the bottom view).

[0069] See also Figure 6 and Figure 7 , which is shown by using the physical field modeling simulation software COMSOL to Figure 3 、 Figure 5 The stress of the block is simulated. Under the same pressure conditions, the location of stress concentration can be seen ( Figure 6 、 Figure 7 The dark area corresponds to Figure 3 、 Figure 5 The area shown in the dotted box.

[0070] like Figure 6 As shown, when the acoustic hole arrangement of this embodiment is adopted, the maximum stress in the stress concentration area is about 3.6 MPa. Figure 7As shown, when the conventional sound hole arrangement is adopted, the maximum stress in the stress concentration area is about 4.4 MPa. It can be seen that the present invention reduces the structural stress by 22% compared with the comparative structure by optimizing the sound hole arrangement.

[0071] Specifically, such as Figure 6 As shown, if a pressure is applied to the bottom surface of the back plate 3 (the side with the height difference), the generated stress will be more evenly distributed in the right-angle area where the "step" and the back edge intersect (on both sides of the opening area), which can effectively reduce the stress magnitude in the stress concentration area and improve the mechanical reliability of the back plate.

[0072] It should be pointed out that, in other embodiments, the opening shape of the peripheral sound hole 5 is not limited to a circle, for example, it can also be a regular polygon, such as a regular hexagon, a regular octagon, and other shapes, which should not overly limit the scope of protection of the present invention.

[0073] As an example, refer back to Figure 1 The MEMS microphone structure also includes a substrate 9, which is located below the diaphragm 1 and supports the backplate 3; a cavity 10 is provided in the substrate 9, and the cavity 10 passes through the substrate 9 in the vertical direction; a bracket 11 is provided between the substrate 9 and the diaphragm 1 to support the diaphragm 1.

[0074] Specifically, the substrate 9 is used to provide a process platform for forming the MEMS microphone structure, and may include but is not limited to a silicon substrate, a germanium substrate, a silicon-germanium substrate, a silicon carbide substrate, a silicon-on-insulator substrate, a germanium-on-insulator substrate, a glass substrate, or a III-V compound substrate (such as a gallium nitride substrate or a gallium arsenide substrate). In this embodiment, the substrate 9 is exemplified by a silicon substrate.

[0075] Specifically, the diaphragm 1, the air gap 6 and the back pole 2 are used to form a capacitor structure. When the microphone is working, the sound signal can enter the capacitor structure (inside the air gap) through the sound hole, and can also enter the capacitor structure through the cavity 10, so that the diaphragm 1 vibrates under the air pressure generated by the sound, and the distance between it and the back pole 2 changes, thereby causing the capacitance value of the capacitor structure to change accordingly, and then converting the sound signal into an electrical signal.

[0076] As an example, the material of the diaphragm 1 includes but is not limited to polysilicon, the material of the back electrode 1 includes but is not limited to polysilicon, the material of the back plate 3 includes but is not limited to silicon nitride, and the material of the bracket 11 includes but is not limited to silicon oxide.

[0077] As an example, the MEMS microphone structure also includes a blocking block 12, which penetrates the back pole 2 in the vertical direction and is connected to the back plate 3, and the distance between the blocking block 12 and the diaphragm 1 is smaller than the distance between the back pole 2 and the diaphragm 1 to prevent the diaphragm 1 from adhering to the back pole 2.

[0078] As an example, the MEMS microphone structure further includes a diaphragm stopper 13 , which is located on the lower surface of the diaphragm 1 to prevent the diaphragm 1 from adhering to the substrate 9 .

[0079] As an example, the MEMS microphone structure further includes air vents 14 extending vertically through the diaphragm. These vents are used to release air through the air vents 14 when the diaphragm 1 is subjected to high pressure, thereby reducing the pressure on the diaphragm 1. The number and distribution of the air vents 14 can be adjusted as needed.

[0080] It should be noted that, depending on different manufacturing processes, the specific form of the diaphragm 1 and the specific form of the back plate 3 may vary. For example, in this embodiment (eg Figure 1 As shown), a portion of the backplate 3 is located on the upper surface of the diaphragm 1. The backplate 3 may be wrapped with an insulating layer 15 in the area outside the diaphragm 1. The insulating layer 15 is a sacrificial layer remaining in the process of forming the air gap 6. An external bracket 16 is provided below the area of the diaphragm 1 pressed by the backplate 3. An annular slit 17 is also provided in the diaphragm 1. The annular slit 17 passes through the diaphragm 1 in the vertical direction to divide the diaphragm 1 from the inside to the outside into a functional part and a non-functional part. The functional part is connected to the substrate 9 via the bracket 11. The vibration of the diaphragm 1 is realized in the functional part, and the non-functional part is connected to the substrate 9 via the external bracket 16. The external bracket 16 and the bracket 11 are made of the same material. In other embodiments, the backplate 3 may not be in contact with the diaphragm 1, and the MEMS microphone structure may not be provided with the external bracket 16, the insulating layer 15, and the annular slit 17. This should not unduly limit the scope of protection of the present invention.

[0081] In summary, the MEMS microphone structure of the present invention optimizes the arrangement and distribution of the acoustic holes, making it easier to control the backplate edge to be located between two concentric circles of peripheral acoustic holes, rather than intersecting the backplate portion with the acoustic holes. This effectively reduces stress concentration at the junction of the backplate edge and the backplate, preventing cracks and damage in areas susceptible to stress concentration, thereby improving the mechanical reliability of the MEMS microphone. Therefore, the present invention effectively overcomes the shortcomings of the prior art and has high industrial application value.

[0082] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the present invention. Anyone skilled in the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by one of ordinary skill in the art without departing from the spirit and technical principles disclosed herein are intended to be covered by the claims of the present invention.

Claims

1. A MEMS microphone structure, characterized in that: include: diaphragm; a back pole, located above the diaphragm and spaced apart from the diaphragm at a preset distance in a vertical direction to form an air gap; a back plate, at least a portion of which is connected to the upper surface of the back electrode to support the back electrode; a central acoustic hole located at the center of the back pole and penetrating the back pole and the back plate in a vertical direction; Multiple peripheral sound holes are distributed around the central sound hole and in concentric circles with the central sound hole as the center. The projection of at least one of the peripheral sound holes on the horizontal plane is located in the area where the back pole is located, and passes through the back pole and the back plate in the vertical direction. The projection of at least one of the peripheral sound holes on the horizontal plane is located outside the area where the back pole is located, and passes through the back plate in the vertical direction. The edge of the back pole and the junction of the back plate do not pass through any of the peripheral sound holes.

2. The MEMS microphone structure according to claim 1, wherein: In the direction from the back pole center to the back pole edge, the number of the peripheral sound holes in the i-th circle is 6i, where i is an integer greater than 0.

3. The MEMS microphone structure according to claim 2, wherein: The 6i peripheral sound holes in the i-th circle are located at the 6i vertices of the regular 6i-gon.

4. The MEMS microphone structure according to claim 3, wherein: In each circle of the peripheral sound holes, two of the peripheral sound holes are located on a first straight line, and the first straight line passes through the center of the back pole.

5. The MEMS microphone structure according to claim 1, wherein: The central sound hole and the peripheral sound holes do not touch each other, and any two adjacent peripheral sound holes do not touch each other. In the direction from the center of the back pole to the edge of the back pole, the distance between the peripheral sound holes and the central sound hole located on the i-th circle is i times D, where D is the distance between the peripheral sound holes and the central sound hole in the first circle, and i is an integer greater than 0.

6. The MEMS microphone structure according to claim 1, wherein: The edge profile of the back pole is circular.

7. The MEMS microphone structure according to claim 1, wherein: The edge of the back pole is located between the i-th circle of peripheral sound holes and the i+1-th circle of peripheral sound holes in the direction from the center of the back pole to the edge of the back pole, and the edge contour of the back pole is a regular 6i-gon or a regular 6(i+1)-gon, where i is an integer greater than 1.

8. The MEMS microphone structure according to claim 1, wherein: The opening shape of the peripheral sound hole is circular or regular polygonal.

9. The MEMS microphone structure according to claim 1, wherein: The MEMS microphone structure further includes: a substrate, located below the diaphragm and supporting the back plate; a cavity located in the substrate and penetrating the substrate in a vertical direction; The bracket is located between the substrate and the diaphragm and is used to support the diaphragm.

10. The MEMS microphone structure according to claim 9, wherein: The MEMS microphone structure also includes a backpole lead-out electrode and a diaphragm lead-out electrode. The backpole lead-out electrode is arranged on the side of the backplate facing away from the diaphragm and penetrates the backplate to connect with the backpole. The diaphragm lead-out electrode is located on the side of the backplate facing away from the diaphragm and penetrates the backplate to connect with the diaphragm.

11. The MEMS microphone structure according to claim 9, wherein: The MEMS microphone structure further includes a blocking block, which vertically penetrates the back pole and is connected to the back plate, and a distance between the blocking block and the diaphragm is smaller than a distance between the back pole and the diaphragm.

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