MEMS microphone
By employing a multi-layered diaphragm design in a MEMS microphone and connecting it to the substrate using an additional layer of material with high yield strength, the problem of diaphragm damage has been solved, resulting in a more robust and stable microphone performance.
Patent Information
- Application Number
- CN202511200500.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Priority Date
- 2025-07-29
- Filing Date
- 2025-08-26
- Publication Date
- 2025-10-31
AI Technical Summary
The diaphragm of existing MEMS microphones is easily damaged during vibration, leading to unstable performance and affecting the microphone's lifespan and reliability.
The diaphragm employs a multi-layer structure design, in which the yield strength of the additional material layer is higher than that of the main diaphragm. It is connected to the substrate through a beam structure to increase the overall strength of the diaphragm, and conductive parts are set on some beam structures to achieve electrical connection.
This improves the stability and robustness of MEMS microphones, reduces the possibility of diaphragm damage, and enhances the microphone's robustness and the reliability of electrical signal output.
Smart Images
Figure CN120881491A_ABST
Abstract
Description
[0001] Cross-reference to related applications
[0002] This invention claims priority to U.S. Patent Application No. 19 / 283,282, filed on July 29, 2025, entitled "MEMS Microphone," the entire contents of which are incorporated herein by reference. Technical Field
[0003] This invention relates to the field of semiconductor device technology, and in particular to a MEMS (Micro-Electro-Mechanical System) microphone. Background Technology
[0004] MEMS microphones are a type of microelectromechanical system (MEMS) microphone that, compared to traditional electret condenser microphones, offers superior acoustic performance, a higher signal-to-noise ratio, better consistent sensitivity, and lower power consumption. MEMS microphones are widely used in smartphones, laptops, and other devices to provide higher voice quality.
[0005] MEMS microphones consist of a backplate and a diaphragm positioned opposite each other, together forming a variable capacitor. The moving structure of the MEMS microphone, such as the diaphragm, bends with the air pressure change caused by sound waves, causing a change in the capacitance of the variable capacitor. This change in capacitance can be used to detect acoustic signals.
[0006] Currently, users have increasingly higher requirements for the stability of MEMS microphones, which means that new materials need to be used to manufacture MEMS microphones, or new improvements need to be made to the structure of MEMS microphones. Summary of the Invention
[0007] The purpose of this invention is to provide a MEMS microphone whose diaphragm adopts a multi-layer structure design and has a higher yield strength in the part connected to the substrate, making the diaphragm more robust and thus forming a more robust and stable MEMS microphone.
[0008] To address the aforementioned technical problems, embodiments of the present invention provide a MEMS microphone, comprising:
[0009] A substrate has a back cavity; a diaphragm is disposed above the back cavity and attached to the substrate; the diaphragm includes a main diaphragm and an additional material layer, the yield strength of the additional material layer being greater than the yield strength of the main diaphragm; the additional material layer includes a first main body portion and N beam structures connecting the first main body portion and the substrate; the main diaphragm includes a main sensing portion and M conductive portions connecting the main sensing portion, wherein the values of N and M satisfy: N > M; the main sensing portion reciprocates relative to the sound pressure direction to change the capacitance and output an electrical signal accordingly, the conductive portions being used to electrically connect the main sensing portion to an external circuit; the first main body portion is at least partially stacked and fixedly disposed with the main sensing portion to improve the strength of the main diaphragm, a single conductive portion is stacked on a single beam structure, the conductive portion being used to electrically connect the main sensing portion to an external circuit.
[0010] Optionally, the orthographic projection of the beam structure along the vibration direction of the diaphragm covers the orthographic projection of the conductive part along the vibration direction of the diaphragm.
[0011] Optionally, the first main body is an annular structure, and the main sensing part includes a second body connected to the inner edge of the first main body and a second extension superimposed on the inner edge of the first main body, wherein the outer edge of the second body is electrically connected to the inner edge of the second extension.
[0012] Optionally, the main membrane is one layer, the additional material layer is two layers, and the main membrane is sandwiched between the two additional material layers, with the two additional material layers covering the main membrane.
[0013] Optionally, the beam structure is provided with conductive vias for exposing the conductive portion.
[0014] Optionally, the conductive part is one, and the conductive part is disposed in any one of the beam structures.
[0015] Optionally, there are an even number of beam structures and two conductive parts, with the two conductive parts respectively disposed on any two symmetrically arranged beam structures.
[0016] Optionally, it also includes multiple anchors located between the diaphragm and the substrate, with each of the multiple anchors corresponding to a multiple of the beam structures, and the beam structures being fixedly connected to the substrate via the anchors.
[0017] Optionally, the anchor is integrally formed with the substrate.
[0018] Optionally, the main film is made of polycrystalline silicon, and the additional material layer is made of silicon nitride.
[0019] In embodiments of the present invention, compared to related technologies, the diaphragm includes a main diaphragm and an additional material layer, the yield strength of which is greater than that of the main diaphragm. The additional material layer includes a first main body portion and N beam structures connecting the first main body portion, the first main body portion being fixedly connected to a substrate via the multiple beam structures. The main diaphragm includes a connected main sensing portion and M conductive portions, the first main body portion being at least partially stacked and fixedly disposed with the main sensing portion, wherein N is greater than M. This configuration, where some beam structures do not have conductive portions, results in a higher yield strength than beam structures with conductive portions, making the overall diaphragm more robust and thus forming a more robust and stable MEMS microphone. Attached Figure Description
[0020] One or more embodiments are illustrated by way of example with reference numerals in the accompanying drawings. These illustrations do not constitute a limitation on the embodiments. Elements with the same reference numerals in the drawings are denoted as similar elements. Unless otherwise stated, the figures in the drawings are not to be limited by scale.
[0021] Figure 1 This is a three-dimensional structural diagram of a MEMS microphone according to an embodiment of the present invention;
[0022] Figure 2 yes Figure 1 A top view of the MEMS microphone shown;
[0023] Figure 3 yes Figure 2 A cross-sectional view along line AA';
[0024] Figure 4 This is a top view schematic diagram of another MEMS microphone according to an embodiment of the present invention;
[0025] Figure 5 yes Figure 4 A cross-sectional view along line BB';
[0026] Figure 6 This is a top view schematic diagram of another MEMS microphone according to an embodiment of the present invention;
[0027] Figure 7 yes Figure 6 A cross-sectional view along line CC';
[0028] Figure 8 This is a three-dimensional structural diagram of another MEMS microphone according to an embodiment of the present invention. Detailed Implementation
[0029] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the various embodiments of the present invention will be described in detail below with reference to the accompanying drawings. However, those skilled in the art will understand that many technical details have been presented in the various embodiments of the present invention to enable the reader to better understand the present invention. However, the technical solutions claimed in the present invention can be implemented even without these technical details and various changes and modifications based on the following embodiments.
[0030] In embodiments of the present invention, the terms "upper," "lower," "left," "right," "front," "rear," "top," "bottom," "inner," "outer," "middle," "vertical," "horizontal," "lateral," and "longitudinal" indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings. These terms are primarily for the purpose of better describing the present invention and its embodiments, and are not intended to limit the indicated devices, elements, or components to having a specific orientation, or to be constructed and operated in a specific orientation.
[0031] Furthermore, in addition to indicating direction or positional relationship, some of the aforementioned terms may also have other meanings. For example, the term "above" may also be used in certain situations to indicate a dependency or connection. Those skilled in the art can understand the specific meaning of these terms in this invention based on the specific circumstances.
[0032] Furthermore, the terms "installation," "setting," "equipped with," "opening," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral structure; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium, or an internal connection between two devices, components, or parts. Those skilled in the art can understand the specific meaning of these terms in this invention according to the specific circumstances.
[0033] Furthermore, the terms "first," "second," etc., are primarily used to distinguish different devices, elements, or components (which may be the same or different in specific type and construction), and are not intended to indicate or imply the relative importance or quantity of the indicated devices, elements, or components. Unless otherwise stated, "a plurality of" means two or more.
[0034] In some MEMS microphones, the diaphragm has a beam structure and is fixed to anchors via the beam structure, thus sealing the cavity of the substrate in the MEMS microphone. A backplate is also placed on the diaphragm, with a gap between the diaphragm and the backplate forming a variable capacitor. When the MEMS microphone is working, the diaphragm vibrates under the influence of sound pressure, bending during vibration to change the capacitance value of the variable capacitor. However, because there is no support between the beam structure and the substrate, during the vibration of the diaphragm, the beam structure not only acts as a stress concentration point for bending deformation but also repeatedly impacts the edge of the substrate, continuing to bear force. This makes the diaphragm extremely susceptible to damage, resulting in unstable performance or easy damage to the MEMS microphone.
[0035] The purpose of this invention is to provide a more robust diaphragm without changing or adding to other structures of the MEMS microphone, thereby forming a more robust and stable MEMS microphone, making the performance of the MEMS microphone more stable and less prone to damage.
[0036] An embodiment of the present invention provides a MEMS microphone, comprising: a substrate having a back cavity; a diaphragm disposed above the back cavity and attached to the substrate; the diaphragm comprising: a main diaphragm and an additional material layer, wherein the yield strength of the additional material layer is greater than the yield strength of the main diaphragm; the additional material layer comprising a first main body portion and N beam structures connecting the first main body portion and the substrate; the main diaphragm comprising a main sensing portion and a conductive portion connecting the main sensing portion, wherein the values of N and M satisfy: N > M; the first main body portion is at least partially stacked and fixedly disposed with the main sensing portion, and a single conductive portion is stacked on a single beam structure, the conductive portion being used to electrically connect the main sensing portion to an external circuit.
[0037] The implementation details of the MEMS microphone in this embodiment are described below. The following content is only for the convenience of understanding and is not necessary for implementing this solution.
[0038] See Figures 1 to 3 In this embodiment, the substrate 101 of the MEMS microphone 100 is configured as an annular shape, such as a square annular shape or a circular annular shape. Taking a square annular substrate 101 as an example, the substrate 101 forms a square back cavity 1011, which extends through the substrate 101 and serves as the vibration space of the MEMS microphone 100. Optionally, the substrate 101 can be a single-crystal silicon substrate or other substrates that meet the design requirements.
[0039] When the substrate 101 is set as a square ring structure, the edges of the outer and inner sides of the substrate 101 can be set as chamfers, especially rounded chamfers, which can reduce the sharp structures inside the MEMS microphone. This is beneficial for product assembly and can also prevent sharp structures on the substrate 101 from contacting and damaging other internal components of the MEMS microphone.
[0040] A diaphragm 102 is disposed above the back cavity 1011 and attached to the substrate 101. The diaphragm 102 includes a main diaphragm 1021 and an additional material layer 1022, the yield strength of which is greater than that of the main diaphragm 1021. The additional material layer 1022 is at least partially laminated with the main diaphragm 1021, and the overlapping portions of the additional material layer 1022 and the main diaphragm 1021 are fixedly connected to each other.
[0041] The additional material layer 1022 is also fixedly connected to the substrate 101, that is, the main film 1021 is connected to the substrate 101 through the additional material layer 1022 and covers the upper side of the back cavity 1011. The yield strength of the additional material layer 1022 is greater than the yield strength of the main film 1021. For example, the additional material layer 1022 can be silicon nitride, and the main film 1021 can be polycrystalline silicon.
[0042] Specifically, the additional material layer 1022 includes a first main body portion 1022a and a plurality of beam structures 1022b connecting the first main body portion 1022a. The first main body portion 1022a is fixedly connected to the substrate 101 through the plurality of beam structures 1022b. The main membrane 1021 includes a main sensing portion 1021a and a conductive portion 1021b connecting the main sensing portion 1021a. The first main body portion 1022a is at least partially stacked with the main sensing portion 1021a, and the stacked portions are fixedly connected to each other. There can be N beam structures 1022b and M conductive portions 1021b, where N is greater than M. In this case, some beam structures 1022b are provided with conductive portions 1021b, while other beam structures 1022b are not provided with conductive portions 1021b. Thus, the beam structure 1022b without conductive part 1021b can be made entirely of silicon nitride. The yield strength of these beam structures 1022b is higher than that of the beam structure 1022b with conductive part 1021b, which makes the overall yield strength of the diaphragm 102 significantly greater than that of existing polycrystalline silicon diaphragms, making it more robust and thus making the MEMS microphone more robust and more resistant to damage.
[0043] The conductive part 1021b and the beam structure 1022b are stacked and arranged to connect the main sensing part 1021a to an external circuit, thereby energizing the main sensing part 1021a. Here, the external circuit refers to the circuit in the MEMS microphone that is electrically connected to the conductive part 1021b, which may be a circuit that provides electrical signals to the main diaphragm 1021 or detects electrical signals from the main diaphragm 1021.
[0044] Understandably, the first main body 1022a and the multiple beam structures 1022b can be integrally formed, and the main sensing part 1021a and the conductive part 1021b can also be integrally formed. The number of beam structures 1022b can be set according to the actual situation, such as three, four or more, and is preferably set to be equally spaced.
[0045] When the conductive part 1021b is provided, the orthogonal projection of the conductive part 1021b on the substrate 101 can be located within the orthogonal projection of the beam structure 1022b on the substrate 101 on which the conductive part 1021b is provided.
[0046] Since the other beam structures 1022b do not have conductive parts 1021b, the mechanical properties of the beam structure 1022b with conductive parts 1021b may differ from those of the other beam structures 1022b. Therefore, the difference in mechanical properties between different parts of the diaphragm 102 can be reduced by designing the diaphragm 102. For example, the number of beam structures 1022b can be appropriately increased to distribute the stress changes during the vibration of the diaphragm 102 more effectively, thereby reducing the stress differences between different beam structures 1022b. Alternatively, the thickness of the conductive parts 1021b can be made smaller, i.e., the thickness of the conductive parts 1021b in the vibration direction of the diaphragm 102 can be minimized to reduce the influence of the conductive parts 1021b on the mechanical properties of the corresponding beam structure 1022b. Alternatively, the dimensions of the conductive portion 1021b in the vibration direction perpendicular to the diaphragm 102 can be reduced, i.e., the width of the conductive portion 1021b can be reduced, which can also reduce the influence of the conductive portion 1021b on the mechanical properties of the beam structure 1022b. Alternatively, identical conductive portions 1021b can be provided on two symmetrical beam structures 1022b to achieve a more balanced stress distribution. In one embodiment, the beam structure 1022b covering the conductive portion 1021b has a greater thickness than the other beam structures 1022b not covered by the conductive portion 1021b. This arrangement can further improve the uniformity of strength of all beam structures, thereby increasing the sensitivity of the main diaphragm.
[0047] See Figure 4 and Figure 5Understandably, when the side of the conductive portion 1021b facing away from the substrate 101 is covered by the beam structure 1022b, the beam structure 1022b is provided with a conductive via 1022c, which exposes the conductive portion 1021b. Thus, the conductive portion 1021b can be electrically connected to an external circuit through the conductive via 1022c. Generally, the conductive via 1022c can be processed by laser cutting, photolithography, plasma etching, or other methods. Furthermore, a material suitable for manufacturing the main film 1021, such as polycrystalline silicon, can be deposited in the conductive via 1022c and electrically connected to the conductive portion 1021b. Thus, when connecting the conductive portion 1021b, the conductive material deposited in the conductive via 1022c can be directly connected.
[0048] It should be noted that silicon nitride is only a preferred material for manufacturing the additional material layer 1022, and is not the only option. In fact, as long as the yield strength of the additional material layer 1022 is greater than that of the main film 1021 made of polycrystalline silicon, and it is an insulating material compatible with the actual manufacturing process, it is acceptable. Polycrystalline silicon is also only one option for manufacturing the main film 1021; other conductive materials that meet the requirements for manufacturing MEMS microphones can be selected depending on the specific circumstances.
[0049] Both the main film 1021 and the additional material layer 1022 can be configured as layered structures. It is understood that the specific values of the yield strength of the additional material layer 1022 and the yield strength of the main film 1021 may vary depending on process conditions, material dimensions, and testing conditions. Generally speaking, the yield strength of silicon nitride is between 3 GPa and 10 GPa, and the yield strength of polycrystalline silicon is between 1 GPa and 3 GPa.
[0050] See you again Figure 2 and Figure 3In one embodiment, the diaphragm 102 includes a two-layer structure, wherein the main diaphragm 1021 is a single layer, and the additional material layer 1022 is a single layer. The main sensing part 1021a includes a second body 1021c connected to the inner edge of the first main body 1022a, and a second extension 1021d stacked on the inner edge of the first main body 1022a, wherein the outer edge of the second body 1021c is electrically connected to the inner edge of the second extension 1021d. For example, the first main body 1022a is configured as a ring structure, and the second body 1021c is disposed in the same layer as the first main body 1022a, located in the hole formed by the first main body 1022a, and fixedly connected to the inner edge of the first main body 1022a surrounding the hole. The second extension 1021d is stacked on top of the first main body 1022a. It can be located on the side of the first main body 1022a facing the substrate 101, or on the side of the first main body 1022a away from the substrate 101. This arrangement ensures that only a portion of the main diaphragm 1021 is covered by the additional material layer 1022 with higher yield strength, maintaining the sensitivity of the diaphragm 102 at a high level. Furthermore, for ease of manufacturing, the main diaphragm 1021 is typically positioned on the same side as the second extension 1021d. It is understood that the second body 1021c and the second extension 1021d can also be disposed in the same layer.
[0051] See Figure 6 and Figure 7 In another embodiment, the diaphragm 102 is also configured with a two-layer structure: a main diaphragm 1021 and an additional material layer 1022. The main diaphragm 1021 and the additional material layer 1022 are stacked, with the orthographic projection of the main diaphragm 1021 onto the substrate 101 falling within the orthographic projection of the additional material layer 1022 onto the substrate 101. In this case, the main diaphragm 1021 can be formed on top of the additional material layer 1022, and can be positioned on the side of the additional material layer 1022 facing the substrate 101, or on the side of the additional material layer 1022 away from the substrate 101. That is, the second body 1021c and the second extension 1021d are co-layered, and in particular, can be configured as an integral structure. With this configuration, the additional material layer 1022, with its higher yield strength, completely covers the main diaphragm 1021, which has a lower yield strength, significantly improving the yield strength of the diaphragm 102 and effectively enhancing the robustness of the MEMS microphone.
[0052] See you again Figure 4 and Figure 5In another embodiment, the diaphragm 102 is configured with a three-layered structure, wherein the main diaphragm 1021 is one layer, the auxiliary material layer 1022 is two layers, and the main diaphragm 1021 is sandwiched between the two auxiliary material layers 1022, forming a sandwich structure of "auxiliary material layer-main diaphragm-auxiliary material layer", and the two auxiliary material layers 1022 cover the main diaphragm 1021. In this way, the diaphragm 102 can be made more robust, greatly enhancing the robustness of the MEMS microphone.
[0053] See Figure 1 and Figure 8 In the various embodiments described above, the edge of the additional material layer 1022 can extend beyond the edge of the back cavity 1011, meaning the diaphragm 102 completely covers the back cavity 1011, which improves the robustness of the MEMS microphone. Alternatively, the edge of the additional material layer 1022 can be within the edge of the back cavity 1011, meaning the diaphragm 102 partially exposes the back cavity 1011, which better maintains the acoustic performance of the MEMS microphone. Generally, the edge of the additional material layer 1022 can be located within the edge of the back cavity 1011, for example, by creating a gap of approximately 1μm-20μm between the edge of the additional material layer 1022 and the edge of the back cavity 1011.
[0054] When the gap width between the edge of the additional material layer 1022 and the edge of the back cavity 1011 is between 1 μm and 8 μm, the additional material layer 1022 has a large area proportion in the diaphragm 102, and the diaphragm 102 as a whole has high yield strength. When the gap width between the edge of the additional material layer 1022 and the edge of the back cavity 1011 is between 9 μm and 15 μm, the additional material layer 1022 has a moderate area proportion in the diaphragm 102, which can better coordinate the overall yield strength and acoustic sensitivity of the diaphragm 102. When the gap width between the edge of the additional material layer 1022 and the edge of the back cavity 1011 is between 16 μm and 20 μm, the additional material layer 1022 has a small area proportion in the diaphragm 102, and the diaphragm 102 has good acoustic sensitivity.
[0055] The main diaphragm 1021 should be located within the area defined by the edge of the back cavity 1011. Theoretically, in the vibration direction perpendicular to the diaphragm 102, the edge of the main diaphragm 1021 should be as far away from the edge of the back cavity 1011 as possible to improve the robustness of the MEMS microphone, but this will affect the electrical performance of the MEMS microphone. Therefore, a gap of about 1μm-50μm can be made between the edge of the main diaphragm 1021 and the edge of the back cavity 1011. In particular, it is preferable that the gap between the edge of the main diaphragm 1021 and the edge of the back cavity 1011 is larger than the gap between the edge of the additional material layer 1022 and the edge of the back cavity 1011.
[0056] See you again Figures 1 to 3In this invention, the MEMS also includes multiple anchors 103 located between the diaphragm 102 and the substrate 101. Each anchor 103 corresponds to a specific beam structure 1022b, which is fixedly connected to the substrate 101 via the anchors 103. This allows the anchors 103 to maintain a certain gap between the diaphragm 102 and the substrate 101, preventing damage to the diaphragm 102 from impact with the edge of the substrate 101 during vibration.
[0057] The anchor 103 is fixedly connected to the substrate 101. For example, it can be integrally formed, with the anchor 103 directly formed on the substrate 101. This can reduce the number of separate components inside the MEMS microphone and improve the robustness of the MEMS microphone.
[0058] The MEMS microphone provided by the embodiments of the present invention has been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only for the purpose of helping to understand the idea of the present invention. There may be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.
Claims
1. A microelectromechanical system (MEMS) microphone, characterized in that, include: The base has a dorsal cavity; A diaphragm is disposed above the back cavity and attached to the substrate; The diaphragm includes a main diaphragm and an additional material layer, wherein the yield strength of the additional material layer is greater than the yield strength of the main diaphragm; The additional material layer includes a first main body and N beam structures connecting the first main body and the substrate; the main film includes a main sensing part and M conductive parts connecting the main sensing part, wherein the values of N and M satisfy: N > M; The main sensing unit reciprocates relative to the sound pressure direction to change the capacitance and output an electrical signal accordingly; the conductive part is used to make electrical connection between the main sensing unit and an external circuit. The first main body portion is at least partially stacked and fixedly disposed with the main sensing portion to improve the strength of the main film, and a single conductive portion is stacked on a single beam structure.
2. The MEMS microphone according to claim 1, characterized in that, The orthographic projection of the conductive part along the vibration direction of the diaphragm lies within the orthographic projection of the beam structure along the vibration direction of the diaphragm.
3. The MEMS microphone according to claim 2, characterized in that, The first main body is a ring structure. The main sensing part includes a second body connected to the inner edge of the first main body and a second extension superimposed on the inner edge of the first main body. The outer edge of the second body is electrically connected to the inner edge of the second extension.
4. The MEMS microphone according to claim 2, characterized in that, The main membrane is one layer, the additional material layer is two layers, and the main membrane is sandwiched between the two additional material layers, with the additional material layer covering the main membrane.
5. The MEMS microphone according to claim 4, characterized in that, The beam structure is provided with conductive vias, which are used to expose the conductive parts.
6. The MEMS microphone according to any one of claims 1-4, characterized in that, The conductive part is one, and the conductive part is disposed in any one of the beam structures.
7. The MEMS microphone according to any one of claims 1-4, characterized in that, There are an even number of beam structures and two conductive parts, which are respectively disposed on any two symmetrically arranged beam structures.
8. The MEMS microphone according to any one of claims 1-4, characterized in that, It also includes multiple anchors located between the diaphragm and the substrate, with each of the multiple anchors and multiple beam structures corresponding to one another, and the beam structures being fixedly connected to the substrate via the anchors.
9. The MEMS microphone according to claim 8, characterized in that, The anchor is integrally formed with the substrate.
10. The MEMS microphone according to any one of claims 1-4, characterized in that, The main film is made of polycrystalline silicon, and the additional material layer is made of silicon nitride.