Vibrating diaphragm and MEMS microphone

Abstract

The embodiment of the invention relates to the technical field of microphones, and discloses a vibrating diaphragm and an MEMS microphone. The vibrating diaphragm comprises a vibrating part and a connecting part arranged around the vibrating part. The vibration part comprises a first flat part located at the middle position, a corrugated part arranged around the first flat part and a second flat part arranged around the corrugated part. The corrugated portion extends in a direction from a center to an edge of the first flat portion. The flexural rigidity of the corrugated part is greater than that of the first flat part and that of the second flat part, and the corrugated part is made of a material at least comprising silicon nitride. According to the vibrating diaphragm and the MEMS microphone provided by the embodiment of the invention, the structural strength of the vibrating diaphragm can be improved.

Description

Technical Field

[0001] The embodiments of the present invention relate to the technical field of microphones, and in particular to a diaphragm and a MEMS microphone. Background Art

[0002] With the continuous development of electronic technology, various electronic devices are becoming more and more functional while becoming smaller and thinner overall. This also means that the space left for the layout of various components in electronic devices is getting smaller and smaller. As an important component in electronic devices, microphones also need to be designed to be small in size to achieve the purpose of occupying less space in view of the limited layout space in electronic devices. MEMS (Micro Electro Mechanical System) microphones are small microphones made using micromachining technology, and have the characteristics of good frequency response characteristics and low noise. At present, MEMS microphones are being widely used in different electronic devices.

[0003] A MEMS microphone includes a substrate, a diaphragm and a back plate, of which the diaphragm is an important component of the MEMS microphone. The structural strength of the diaphragm affects the normal operation of the MEMS microphone. Therefore, how to improve the structural strength of the diaphragm is an important issue. Summary of the invention

[0004] The purpose of the embodiments of the present invention is to provide a diaphragm and a MEMS microphone, which can improve the structural strength of the diaphragm.

[0005] In order to solve the above technical problems, an embodiment of the present invention provides a diaphragm. The diaphragm includes a vibrating portion and a connecting portion arranged around the vibrating portion. The vibrating portion includes a first flat portion located in the middle, a corrugated portion arranged around the first flat portion, and a second flat portion arranged around the corrugated portion. The corrugated portion extends from the center to the edge of the first flat portion. The bending stiffness of the corrugated portion is greater than the bending stiffness of the first flat portion and the second flat portion, and the corrugated portion is made of a material including at least silicon nitride.

[0006] The embodiment of the present invention further provides a MEMS microphone, which includes a substrate having a back cavity and a capacitor structure disposed on the substrate. The capacitor structure includes a diaphragm and a back plate spaced apart from the diaphragm, and the diaphragm is the above-mentioned diaphragm.

[0007] The diaphragm and MEMS microphone provided by the embodiments of the present invention are made of a material including at least silicon nitride at the corrugated structure, so that the bending stiffness of the corrugated part is greater than the bending stiffness of other parts. By using a material with higher bending stiffness than other parts at the corrugated structure, the corrugated part has a higher structural strength than other parts, thereby reducing the risk of diaphragm rupture failure.

[0008] In some embodiments, the first flat portion and the second flat portion are made of polysilicon material, and the corrugated portion is made of silicon nitride material. In this way, the structural strength of the corrugated portion can be effectively improved by using silicon nitride, which has better bending stiffness than polysilicon, to make the corrugated portion.

[0009] In some embodiments, the corrugated portion includes a base layer connected to the first flat portion at one end and to the second flat portion at the other end, and a reinforcing layer covering the base layer, wherein the reinforcing layer is made of silicon nitride material. In this way, a reinforcing layer with higher bending stiffness is used at the corrugated structure to adhere to the corrugated structure, so that the corrugated portion has a higher structural strength than other parts.

[0010] In some embodiments, the substrate layer is made of polysilicon or silicon nitride. In this way, the material of the substrate layer of the corrugated portion can be selected according to actual needs.

[0011] In some embodiments, the reinforcing layer completely covers the substrate layer in the direction from the center to the edge of the first flat portion. In this way, the structural strength of any position of the substrate layer can be improved by making the reinforcing layer completely cover the substrate layer.

[0012] In some embodiments, the substrate layer includes concave portions and convex portions alternately arranged along the direction from the center to the edge of the first flat portion, and there are multiple reinforcing layers in the direction from the center to the edge of the first flat portion, each reinforcing layer completely covers a concave portion and a portion of the convex portion adjacent to the concave portion, and there is a gap between the edges of adjacent reinforcing layers located on the same convex portion. In this way, the reinforcing layer can be arranged at the weak position of the substrate layer to improve the structural strength of the weak position of the substrate layer.

[0013] In some embodiments, a protrusion extends from one side of the first flat portion and the second flat portion near the end of the corrugated portion, and the protrusion covers the edge of the corrugated portion. In this way, the connection reliability between the flat portion and the corrugated portion can be enhanced by the protrusion.

[0014] In some embodiments, the thickness of the corrugated portion is less than the thickness of the flat portion. In this way, the mechanical sensitivity of the corrugated portion can be ensured by reducing the thickness of the corrugated portion while providing the corrugated portion with sufficient bending rigidity.

[0015] In some embodiments, the reinforcement layer of the diaphragm is disposed on a side of the corrugated portion close to the back plate and / or a side of the corrugated portion away from the back plate. In this way, the bending rigidity of the corrugated portion can be improved by disposing the reinforcement layer on one side of the corrugated portion or on both sides of the corrugated portion. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] One or more embodiments are exemplarily described by pictures in the corresponding drawings, and these exemplified descriptions do not constitute limitations on the embodiments. Elements with the same reference numerals in the drawings represent similar elements, and unless otherwise stated, the figures in the drawings do not constitute proportional limitations.

[0017] Figure 1 is a schematic diagram of a partial structure of a diaphragm provided in some embodiments of the present invention;

[0018] Figure 2 is along Figure 1 Schematic diagram of the cross-sectional structure along the AA direction;

[0019] Figure 3 is a schematic diagram of a partial structure of a diaphragm provided in some other embodiments of the present invention;

[0020] Figure 4 is along Figure 3 Schematic diagram of the cross-sectional structure along the middle BB direction;

[0021] Figure 5 Schematic diagrams of cross-sectional structures of diaphragms provided in some other embodiments of the present invention;

[0022] Figure 6 is a schematic diagram of the structure of a MEMS microphone provided by some embodiments of the present invention;

[0023] Figure 7 It is a schematic diagram of the local structure of the diaphragm and the back plate in the MEMS microphone provided by some embodiments of the present invention when they cooperate with each other. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical scheme and advantages of the embodiments of the present invention clearer, the embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings. However, it can be understood by those skilled in the art that in the embodiments of the present invention, many technical details are proposed in order to enable readers to better understand the present invention. However, even without these technical details and various changes and modifications based on the following embodiments, the technical scheme claimed in the present invention can also be implemented. The division of the following embodiments is for the convenience of description and should not constitute any limitation on the specific implementation of the present invention. The various embodiments can be combined and referenced with each other without contradiction.

[0025] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by technicians in the technical field to which the present invention belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention; the terms "including" and "having" in the specification and claims of the present invention and the above-mentioned figure descriptions and any variations thereof are intended to cover non-exclusive inclusions.

[0026] In the description of the embodiments of the present invention, unless otherwise clearly specified and limited, technical terms such as "installed", "connected", "connected" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the embodiments of the present invention can be understood according to specific circumstances.

[0027] A MEMS microphone includes a diaphragm and a backplate, which are processed on a silicon substrate through a micromachining process. The backplate has perforations, and there is an air gap between the diaphragm and the backplate, forming a variable air gap capacitor. When the diaphragm vibrates in response to external sound waves or sound pressure shocks, the capacitor can convert the sound energy into electrical energy for detection.

[0028] MEMS microphones are easy to integrate into various electronic devices due to their small size. However, the sensitivity of the microphone will be sacrificed when the size is reduced. In actual situations, the sensitivity of the MEMS microphone can be improved by controlling the low stress of the diaphragm in the MEMS microphone. In addition, the power consumption can be greatly reduced.

[0029] Generally, residual stress may form on the diaphragm during the manufacturing or operation process. The residual stress of the diaphragm is an important factor leading to reduced sensitivity. Excessive residual stress will lead to a decrease in the flexibility of the diaphragm and affect the vibration characteristics of the diaphragm. In order to reduce the residual stress of the diaphragm and improve the compliance of the diaphragm, a corrugated diaphragm has emerged, that is, the diaphragm is provided with a corrugated structure. The corrugated structure can improve the mechanical sensitivity of the diaphragm. The number and depth of the corrugations can be set according to actual conditions. When the diaphragm is actually processed, as the depth of the corrugations increases, the diaphragm will be damaged during the process.

[0030] When a corrugated structure is provided on the diaphragm, high stress will be concentrated on the edge of the corrugation, resulting in insufficient strength at the corrugated structure, making the diaphragm prone to rupture and failure. In order to improve the strength of the diaphragm, some embodiments of the present invention provide a diaphragm. The corrugated structure of the diaphragm is replaced with a material with a higher bending stiffness than the bending stiffness of the diaphragm body, or a reinforcing layer with a higher bending stiffness than the bending stiffness of the diaphragm body is attached to the corrugated structure of the diaphragm. In this way, the strength of the corrugated structure of the diaphragm can be improved, and the ability of the corrugated structure to resist deformation can be improved. The phenomenon of easy bending and rupture of the corrugated structure of the diaphragm is avoided, thereby improving the structural strength of the diaphragm.

[0031] Combine the following Figures 1 to 5 The diaphragms provided by some embodiments of the present invention are described.

[0032] like Figures 1 to 5 As shown, the diaphragm 11 provided in some embodiments of the present invention includes a vibration portion 111 and a connection portion 112 arranged around the vibration portion 111. The vibration portion 111 includes a first flat portion 1111 located in the middle, a corrugated portion 1112 arranged around the first flat portion 1111, and a second flat portion 1113 arranged around the corrugated portion. The corrugated portion 1112 extends from the center to the edge of the first flat portion 1111. The bending stiffness of the corrugated portion 1112 is greater than the bending stiffness of the first flat portion 1111 and the second flat portion 1113, and the corrugated portion 1112 is made of a material including at least silicon nitride.

[0033] The vibration part 111 is the part of the diaphragm 11 that vibrates in response to sound waves, and the connection part 112 is the part of the diaphragm 11 that is connected to the substrate and fixed on the substrate. The vibration part 111 of the diaphragm 11 is opposite to the back plate, one side of the vibration part 111 faces the back plate, and the other side of the vibration part 111 faces the back cavity of the substrate. Usually the back plate does not deform, so the vibration displacement of the diaphragm 11 affects the capacitance value, thereby affecting the sensitivity of the microphone. The corrugated structure formed by the corrugated part 1112 improves the sensitivity of the diaphragm 11.

[0034] The corrugated portion 1112 is arranged around the first flat portion 1111, and the first flat portion 1111 occupies the central position of the vibration portion 111, and can respond promptly under the action of sound pressure. The corrugated portion 1112 can be located near the edge of the vibration portion 111. A relatively flat portion can also be arranged on the side of the corrugated portion 1112 away from the flat portion 1111, that is, the corrugated portion 1112 is arranged on the edge of the vibration portion 111, and has a certain interval with the connecting portion 112, and the connecting portion 112 is connected to the second flat portion 1113. In order to balance the air pressure on both sides of the diaphragm 11, a through hole is arranged on the vibration portion 111, and the through hole can make the air flow flow relatively on both sides of the diaphragm 11, so that the air pressure on both sides of the diaphragm 11 is balanced to a certain extent.

[0035] The corrugated structure formed by the corrugated portion 1112 makes the corrugated portion 1112 have a shape different from the first flat portion 1111 and the second flat portion 1113, which is beneficial to reduce the stress across the diaphragm 11. The arrangement of the corrugated structure can improve compliance. At the same time, the corrugated portion 1112 is also prone to the risk of rupture failure due to the presence of corrugations, or folds. The deeper the folds and the sharper the shape, the higher the risk of rupture failure of the diaphragm 11.

[0036] In view of the relative fragility of the corrugated portion 1112 due to the presence of wrinkles, the diaphragm 11 provided in some embodiments of the present invention is made of a material including at least silicon nitride at the corrugated structure, so that the bending rigidity of the corrugated portion is greater than the bending rigidity of other parts. By using a material with higher bending rigidity at the corrugated structure than other parts, the corrugated structure formed by the corrugated portion 1112 has a higher structural strength than other parts, thereby reducing the risk of rupture and failure of the diaphragm 11.

[0037] In actual situations, other parts of the diaphragm 11 can be made of polysilicon, while the corrugated structure can be made of silicon nitride, that is, the first flat portion 1111 and the second flat portion 1113 can be made of polysilicon material, and the corrugated portion 1112 can be made of silicon nitride material. Alternatively, graphene can be used as a reinforcing material to improve the bending stiffness of the corrugated structure of the diaphragm 11. Alternatively, other materials with higher bending stiffness can be used as the manufacturing material of the corrugated portion 1112. In addition, during the manufacturing process of the diaphragm 11, deposition and etching processes can be used for a variety of materials, so that materials with different bending stiffness can be integrated in different parts.

[0038] like Figure 1 and Figure 2 As shown, the corrugated portion 1112 of the diaphragm 11 can be made of a material with higher bending stiffness to replace the material with the same bending stiffness as other parts in the prior art.

[0039] Continue reading Figure 1 and Figure 2 A protruding portion 1114 may extend from one side of the end of the first flat portion 1111 and the second flat portion 1113 close to the corrugated portion 1112 , and the protruding portion 1114 covers the edge of the corrugated portion 1112 .

[0040] The protrusion 1114 provided at the edge of the first flat portion 1111 and the second flat portion 1113 can be integrally formed with the first flat portion 1111 and the second flat portion 1113 to constitute a part of the first flat portion 1111 and the second flat portion 1113. At the same time, the protrusion 1114 covers the edge of the corrugated portion 1112. Through the covering of the corrugated portion 1112 by the protrusion 1114, an additional connection portion is formed at the connection between the edge of the first flat portion 1111 and the edge of the corrugated portion 1112, and at the connection between the edge of the second flat portion 1113 and the edge of the corrugated portion 1112. That is, the protrusion 1114 establishes a new connection form between the first flat portion 1111 and the corrugated portion 1112, and between the second flat portion 1113 and the corrugated portion 1112, so that the protrusion 1114 is attached to the corrugated portion 1112. In this way, when the first flat portion 1111 and the second flat portion 1113 are made of a material different from that of the corrugated portion 1112, the connection between the first flat portion 1111 and the corrugated portion 1112, and the connection between the second flat portion 1113 and the corrugated portion 1112 can be strengthened by forming relatively protruding portions at the edges of the first flat portion 1111 and the second flat portion 1113.

[0041] In actual situations, the protrusions 1114 may be formed on both sides of the end of the first flat portion 1111 close to the corrugated portion 1113 or the end of the second flat portion 1113 close to the corrugated portion 1112, so as to wrap the edge of the corrugated portion 1112. Thus, the edge of the corrugated portion 1112 is inserted into the first flat portion 1111 or the second flat portion 1113. The connection between the corrugated portion 1112 and the first flat portion 1111 or the connection between the corrugated portion 1112 and the second flat portion 1113 may also be overlapped, which can also increase the connection and matching area between the corrugated portion 1112 and the first flat portion 1111 or between the corrugated portion 1112 and the second flat portion 1113.

[0042] In some embodiments, the thickness of the corrugated portion 1112 is less than the thickness of the first flat portion 1111 .

[0043] When the entire corrugated portion 1112 is made of a material with higher bending rigidity, the thickness of the corrugated portion 1112 can be reduced to improve the mechanical sensitivity.

[0044] like Figures 3 to 5As shown, when the corrugated structure of the diaphragm 11 is reinforced, a reinforcing layer 102 may also be provided in the corrugated portion 1112. By providing a reinforcing layer 102 having a higher bending stiffness, the bending stiffness of the corrugated portion 1112 is reinforced. The reinforcing layer 102 may be provided at the top of the corrugated portion 1112. In actual situations, the reinforcing layer 102 may also be provided at the bottom of the corrugated portion 1112, or at the top and bottom of the corrugated portion 1112 at the same time. That is, the reinforcing layer 102 may be provided on one side of the corrugated portion 1112 close to the back plate and / or on one side of the corrugated portion 1112 away from the back plate.

[0045] When the reinforcing layer 102 is attached, the corrugated portion 1112 may include a substrate layer 101 connected to the first flat portion 1111 at one end and to the second flat portion 1113 at the other end, and a reinforcing layer 102 covering the substrate layer 101 , wherein the reinforcing layer 102 is made of silicon nitride material.

[0046] The base layer 101 can be made of polysilicon material, and when the base layer 101 of the corrugated structure has the same bending stiffness as other parts, the reinforcing layer 102 with higher bending stiffness is used to adhere the corrugated structure, so that the corrugated part 1112 has a higher structural strength than other parts.

[0047] When the corrugated portion 1112 forms a multi-layer structure, the adverse effects of the substrate layer 101 with lower bending stiffness due to high stress concentration can be offset or partially eliminated by the reinforcing layer 102 with higher bending stiffness. By attaching the reinforcing layer 102 with higher bending stiffness, the anti-deformation ability of the corrugated portion 1112 is improved, and the risk of rupture failure is reduced.

[0048] In actual situations, the substrate layer 101 may also be made of silicon nitride material, thereby forming a multi-layer silicon nitride structure including the substrate layer 101 and the reinforcement layer 102 , which effectively ensures the structural strength of the corrugated structure.

[0049] like Figure 4 As shown, in some embodiments, the reinforcement layer 102 may completely cover the substrate layer 101 in a direction from the center to the edge of the first flat portion 1111 .

[0050] That is, the reinforcing layer 102 can completely cover the base layer 101, which can facilitate the molding and manufacturing of the reinforcing layer 102 and ensure the overall structural strength of the reinforcing layer 102. When attaching the reinforcing layer 102, the reinforcing layer 102 can cover only one side of the base layer 101, or cover both sides of the base layer 101 at the same time.

[0051] In addition, the reinforcement layer 102 may also cover only a portion of the base layer 101. Figure 5As shown, in some embodiments, the substrate layer 101 may include concave portions 1011 and convex portions 1012 alternately arranged in a direction from the center to the edge of the first flat portion 1111, and there are multiple reinforcing layers 102 in a direction from the center to the edge of the first flat portion 1111, each reinforcing layer 102 completely covers a concave portion 1011 and a portion of the convex portion 1012 adjacent to the concave portion 1011, and there is a gap between the edges of adjacent reinforcing layers 102 located on the same convex portion 1012.

[0052] That is, the reinforcing layer 102 is attached to the base layer 101 in a dispersed manner, and each reinforcing layer 102 is arranged corresponding to the concave portion 1011 and part of the convex portion 1012 of the base layer 101. This can save the material of the reinforcing layer 102, and at the same time, can ensure the mechanical sensitivity of the base layer 101 where the reinforcing layer 102 is not attached.

[0053] In some embodiments, each concave portion 1011 and each convex portion 1012 may have a certain straight extension length, so that the curved portion does not have wrinkles formed in a sharp shape due to being directly connected together. By forming the corrugated structure with smooth edges without sharp corners, stress concentration in the corrugated structure can be avoided. The use of smooth edges reduces the failure rate of the diaphragm 11 during operation, which is conducive to increasing the product life.

[0054] In addition, the thickness of the reinforcement layer 102 may be smaller than the thickness of the base layer 101 .

[0055] The reinforcing layer 102 can be attached to the base material layer 101 in a form of relatively small thickness, which can enhance the bending rigidity of the corrugated structure without causing adverse effects on the characteristics of the corrugated portion 1112 itself.

[0056] In some embodiments, the connection between the corrugated portion 1112 and the first flat portion 1111 and the connection between the corrugated portion 1112 and the second flat portion 1113 may remain flush.

[0057] That is, the corrugated portion 1112 has the same thickness as the first flat portion 1111 and the second flat portion 1113 at the edge, and when the corrugated portion 1112 is connected to the first flat portion 1111 and the second flat portion 1113, the two side surfaces are in an aligned state (the same horizontal state). In this way, the corrugated portion 1112 and the first flat portion 1111 and the second flat portion 1113 are in the same plane at the connection, and positioning is simple. The manufacturing process of the diaphragm 11 can be simplified, which is conducive to forming a diaphragm 11 integrated with different materials through deposition and etching processes.

[0058] Some embodiments of the present invention also provide a MEMS microphone. Figure 6 and Figure 7As shown, the MEMS microphone includes a substrate 10 having a back cavity and a capacitor structure disposed on the substrate 10. The capacitor structure includes a diaphragm 11 and a back plate 12 spaced apart from the diaphragm 11, and the diaphragm 11 is the above-mentioned diaphragm 11.

[0059] A vibration gap is formed between the vibration part 111 of the diaphragm 11 and the back plate 12, and a capacitor structure is formed. When the vibration part 111 of the diaphragm 11 is affected by a sound wave signal, the diaphragm 11 vibrates, and the distance between the diaphragm 11 and the back plate 12 changes, resulting in a change in capacitance. The sound wave signal is thereby converted into an electrical signal. By using a corrugated part 1112 with higher bending stiffness, or by using a reinforcing layer 102 to increase the bending stiffness of the corrugated part 1112, the impact resistance of the diaphragm 11 is improved, and the probability of rupture and failure of the diaphragm 11 is reduced. The reinforcing layer 102 can be arranged on a side of the corrugated part 1112 close to the back plate 12 and / or a side of the corrugated part 1112 away from the back plate 12.

[0060] Those skilled in the art will appreciate that the above-mentioned embodiments are specific examples for implementing the present invention, and in actual applications, various changes may be made thereto in form and detail without departing from the spirit and scope of the present invention.

Claims

1. A diaphragm, characterized in that: The invention comprises a vibration part and a connection part arranged around the vibration part, wherein the vibration part comprises a first flat part located in the middle, a corrugated part arranged around the first flat part and a second flat part arranged around the corrugated part, wherein the corrugated part extends from the center to the edge of the first flat part, the bending stiffness of the corrugated part is greater than the bending stiffness of the first flat part and the second flat part, and the corrugated part is made of a material at least including silicon nitride.

2. The diaphragm according to claim 1, characterized in that: The first flat portion and the second flat portion are made of polysilicon material, and the corrugated portion is made of silicon nitride material.

3. The diaphragm according to claim 1, characterized in that: The corrugated portion includes a base layer having one end connected to the first flat portion and the other end connected to the second flat portion, and a reinforcement layer covering the base layer, wherein the reinforcement layer is made of silicon nitride material.

4. The diaphragm according to claim 3, characterized in that: The substrate layer is made of polysilicon or silicon nitride material.

5. The diaphragm according to claim 3, characterized in that: The reinforcement layer completely covers the base material layer in a direction from the center to the edge of the first flat portion.

6. The diaphragm according to claim 3, characterized in that: The base material layer includes concave portions and convex portions alternately arranged in the direction from the center to the edge of the first flat portion. The reinforcing layer has multiple portions in the direction from the center to the edge of the first flat portion. Each reinforcing layer completely covers one concave portion and a portion of the convex portion adjacent to the concave portion. There is a gap between the edges of two adjacent reinforcing layers located on the same convex portion.

7. The diaphragm according to claim 1, characterized in that: A protruding portion extends from one side of the first flat portion and the second flat portion close to the end of the corrugated portion, and the protruding portion covers the edge of the corrugated portion.

8. The diaphragm according to claim 7, characterized in that: The thickness of the corrugated portion is smaller than the thickness of the first flat portion.

9. A MEMS microphone, comprising a substrate having a back cavity and a capacitor structure arranged on the substrate, characterized in that: The capacitor structure includes a diaphragm and a back plate spaced apart from the diaphragm, and the diaphragm is the diaphragm according to any one of claims 1 to 8.

10. The MEMS microphone according to claim 9, characterized in that: The corrugated portion of the diaphragm includes a base layer connected to the first flat portion at one end and to the second flat portion at the other end, and a reinforcement layer covering the base layer, wherein the reinforcement layer is made of silicon nitride material and is arranged on a side of the corrugated portion close to the back plate and / or a side of the corrugated portion away from the back plate.

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