A MEMS diaphragm and a MEMS sensor

Abstract

The application discloses a kind of MEMS diaphragm and MEMS sensor, MEMS diaphragm includes: main diaphragm, main diaphragm includes main body sensing part and fixed part, several fixed parts annularly spaced connection on the outer edge of main body sensing part;Additional material layer, additional material layer is arranged on fixed part, or, additional material layer is arranged on the edge of main body sensing part and fixed part;Wherein, the internal stress of additional material layer is greater than the internal stress of main body sensing part.Compared with prior art, by being provided with additional material layer on main diaphragm, additional material layer mechanically reinforces the membrane area that experiences high stress in pressure pulse, and the internal stress of additional material layer is greater than the internal stress of main body sensing part, so as to guarantee the compliance of main diaphragm.

Description

Technical Field

[0001] This invention relates to the field of microelectromechanical systems (MEMS) technology, and in particular to a MEMS diaphragm and a MEMS sensor. Background Technology

[0002] The diaphragms used in MEMS devices such as MEMS microphones have many limitations in terms of performance, manufacturability, and cost.

[0003] Common constraints include limiting diaphragm size due to the correlation between mold size and cost, minimum compliance requirements to meet target sensitivity and robustness, or reliability targets that limit the maximum stress the diaphragm may withstand due to pressure shocks. These constraints are often contradictory; smaller diaphragms are inherently less compliant, and highly compliant diaphragms are inherently less robust because they deform more under a given pressure shock.

[0004] In traditional membranes, the design space is typically limited to a single-material membrane with simple anchor beams perpendicular to the membrane edge. These membranes often need to be large (e.g., 1 mm in diameter) to meet compliance requirements while maintaining robustness. Furthermore, the robustness of these membranes is often limited by several weak areas at the beam anchor points, leading to stress concentration during pressure pulses.

[0005] In traditional membranes, additional material layers can be added to reinforce areas experiencing the highest stress during pressure shocks, such as beams. However, such additional material layers can lead to a significant reduction in membrane compliance, thereby decreasing MEMS sensitivity. The additional material layers typically have similar internal stresses to the host membrane material and generally do not extend in a loop around the entire circumference of the membrane. Summary of the Invention

[0006] The purpose of this invention is to provide a MEMS diaphragm and a MEMS sensor to solve the technical problems in the prior art. It can significantly improve the robustness of the diaphragm without affecting its flexibility and diaphragm size. This is achieved by utilizing the ring stress in the additional material ring when its inherent stress is higher than that of the main diaphragm material.

[0007] In a first aspect, the present invention provides a MEMS film, comprising:

[0008] A main diaphragm, the main diaphragm including a main sensing part and a fixing part, wherein a plurality of the fixing parts are circumferentially spaced and connected to the outer edge of the main sensing part;

[0009] An additional material layer is disposed on the fixing part, or the additional material layer is disposed on the edge of the main sensing part and on the fixing part;

[0010] The internal stress of the additional material layer is greater than the internal stress of the main sensing part.

[0011] In the MEMS film described above, preferably, the additional material layer is embedded within the main sensing part.

[0012] In the MEMS film described above, preferably, the additional material is stacked on top of or at the bottom of the main sensing part.

[0013] In the MEMS film described above, preferably, the additional material layer has a plurality of through holes.

[0014] In the MEMS film described above, preferably, the additional material layer has a plurality of concentrically arranged annular grooves, and the plurality of annular grooves are arranged sequentially at intervals along the radial direction of the main sensing part.

[0015] In the MEMS film described above, preferably, the additional material layer is provided with a plurality of strip grooves, and the plurality of strip grooves are arranged in a ring with the axis of the main sensing part as the center line.

[0016] In the MEMS diaphragm described above, preferably, the fixing part includes a fixing section and a connecting section, one end of the connecting section is connected to the middle of the fixing section, and the other end of the connecting section is connected to the main sensing part.

[0017] In the MEMS diaphragm described above, preferably, arc-shaped notches are formed on both sides of the connecting segment.

[0018] In the MEMS diaphragm described above, preferably, the fixed section has anchoring portions at both ends.

[0019] In the MEMS film described above, preferably, the additional material layer is made of silicon nitride, has a stress of more than 100 MPa and no stress gradient, and the main film is made of polycrystalline silicon and has a stress gradient.

[0020] Secondly, the present invention also provides a MEMS sensor, the MEMS sensor comprising the aforementioned MEMS diaphragm.

[0021] Compared with the prior art, the present invention provides an additional material layer on the main diaphragm, which mechanically reinforces the diaphragm region that experiences high stress during pressure pulses, and the internal stress of the additional material layer is greater than the internal stress of the main sensing part, thereby ensuring the flexibility of the main diaphragm. Attached Figure Description

[0022] Figure 1This is a schematic diagram of the structure of the main diaphragm provided in an embodiment of the present invention;

[0023] Figure 2 This is a schematic diagram of the structure of the main diaphragm provided in the embodiment of the present invention, in which an additional material layer is disposed;

[0024] Figure 3 This is a schematic diagram of the structure provided in an embodiment of the present invention, in which an additional material layer is embedded within the main sensing part;

[0025] Figure 4 This is a schematic diagram of the structure provided in an embodiment of the present invention, showing the additional material layered on top of the main sensing part;

[0026] Figure 5 This is a schematic diagram of the structure provided in the embodiment of the present invention, in which the additional material is stacked at the bottom of the main sensing part;

[0027] Figure 6 This is a schematic diagram of the first type of structure with the additional material layer and the main diaphragm assembled.

[0028] Figure 7 This is a schematic diagram of the second type of structure with the additional material layer and the main diaphragm assembled.

[0029] Figure 8 This is a schematic diagram of the third type of structure with the additional material layer and the main diaphragm assembled.

[0030] Figure 9 This is a schematic diagram of the fourth type of structure with the additional material layer and the main diaphragm assembled.

[0031] Figure 10 This is a schematic diagram of the fifth type of structure with the additional material layer and the main diaphragm assembled.

[0032] Figure 11 This is a schematic diagram of the compliance curve of the main diaphragm under zero applied pressure;

[0033] Figure 12 This is a schematic diagram of the compliance curve of the main diaphragm under a pressure of 50 Pa.

[0034] Figure 13 This is a schematic diagram of the center stress curve of the main diaphragm.

[0035] Explanation of reference numerals in the attached figures:

[0036] 10-Main diaphragm, 11-Main sensing part, 12-Fixing part, 121-Fixing section, 122-Connecting section, 123-Arc-shaped notch, 13-Anchoring part;

[0037] 20 - Additional material layer, 21 - Through hole, 22 - Annular groove, 23 - Strip groove. Detailed Implementation

[0038] The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0039] like Figure 1 as well as Figure 2 As shown, the present invention provides a MEMS film, including a main film 10 and an additional material layer 20, wherein:

[0040] The main diaphragm 10 includes a main sensing part 11 and a fixing part 12. A plurality of fixing parts 12 are connected to the outer edge of the main sensing part 11 in a ring at intervals. In one feasible embodiment, the main diaphragm 10 is fixed on a substrate (not shown). A back cavity is provided through the axial direction of the substrate. Preferably, the inner contour surface of the back cavity is a circular groove structure. The fixing part 12 is used to suspend the main sensing part 11 and cover it through the back cavity. The main sensing part 11 is used to sense sound pressure. Under the action of sound pressure, the main sensing part 11 reciprocates relative to the sound pressure direction, which causes the capacitance to change and outputs an electrical signal accordingly.

[0041] Reference Figure 1 as well as Figure 2 As shown, the fixing part 12 includes a fixing section 121 and a connecting section 122. One end of the connecting section 122 is connected to the middle of the fixing section 121, and the other end of the connecting section 122 is connected to the main sensing part 11. In one feasible embodiment, the fixing section 121 is a strip structure, and anchoring parts 13 are provided at both ends of the fixing section 121. The fixing section 121 is fixed to the substrate by the anchoring parts 13. The connecting section 122 can also be a strip structure. The long axis direction of the connecting section 122 is perpendicular to the long axis direction of the fixing section 121. The fixing section 121 has a larger area, which can increase the contact area with the substrate and improve the reliability of the fixed connection. The connecting section 122 has a smaller area, which can reduce the constraint on the main sensing part 11 and improve the flexibility of the main sensing part 11.

[0042] Reference Figure 1 As shown, arc-shaped notches 123 are formed on both sides of the connecting section 122, and a smooth transition connection is formed between the fixing section 121 and the main sensing part 11, which can reduce stress concentration, improve the mechanical sensitivity of the main sensing part 11, and increase the reliability of the MEMS diaphragm.

[0043] In the embodiments provided in this application, the material of the main sensing part 11 can be polycrystalline silicon. The main sensing part 11 is circular, and six fixing parts 12 are equally spaced and arranged in a ring around the circumference of the main sensing part 11. Those skilled in the art will know that the shape of the main sensing part 11 can be other shapes, such as square, etc. The number of fixing parts 12 can also be increased or decreased. The layout of the fixing parts 12 can be determined according to the shape of the main sensing part 11, and is not limited here.

[0044] By distributing the fixing part 12 on the outer edge of the main sensing part 11, the flexibility of the main sensing part 11 is improved, making the radius of curvature of the main sensing part 11 larger, thereby generating a larger output signal. Since the deflection of the main diaphragm 10 is parabolic, the deflection of the main sensing part 11 at the center is the largest, and the deflection of the fixing part 12 at the edge is smaller. By placing the main sensing part 11 at the place where the main diaphragm 10 moves most violently, that is, at the middle of the main diaphragm 10, and not placing the main sensing part 11 at the edge of the main diaphragm 10, the sensitivity of the main diaphragm 10 can be improved.

[0045] Reference Figure 2 , Figure 6 as well as Figure 7 As shown, the additional material layer 20 is disposed on the fixing part 12, or the additional material layer 20 is disposed on the edge of the main sensing part 11 and on the fixing part 12, such as... Figure 6 As shown, when the additional material layer 20 is simultaneously located on both the edge of the main sensing part 11 and the fixing part 12, the additional material layer 20 on the main sensing part 11 is annular, and the annular additional material layer 20 is disposed in the area of ​​the main sensing part 11 where deformation is small. The shape of the additional material layer 20 on the fixing part 12 is adapted to the shape of the fixing part 12. By adding the additional material layer 20, the membrane area experiencing high stress in the pressure pulse is mechanically reinforced, and the robustness of the main diaphragm 10 is significantly improved without affecting the membrane size.

[0046] To avoid the presence of the additional material layer 20 causing the main sensing part 11 to harden and thus reduce the flexibility of the main sensing part 11, the internal stress of the additional material layer 20 is greater than the internal stress of the main sensing part 11. In the embodiments provided in this application, the internal stress of the additional material layer 20 is higher than 100 MPa. The internal stress of the additional material layer 20 is transferred to the main sensing part 11, thereby overcoming the stiffness effect caused by adding more thickness of the additional material layer 20 at the edge of the main sensing part 11, and improving the robustness of the main sensing part 11 without affecting the flexibility and film size of the main sensing part 11.

[0047] In the embodiments provided in this application, the material of the additional material layer 20 is silicon nitride, which has a stress of more than 100 MPa and no stress gradient, while the material of the main diaphragm 10 is polycrystalline silicon and has a stress gradient. Those skilled in the art will know that the materials of the additional material layer 20 and the main diaphragm 10 can be adaptively matched according to actual needs.

[0048] This influence on the compliance of the ring of the additional material layer 20 is due to the circumferential stress caused by the intrinsic tensile stress of the additional material layer 20. The effect of the circumferential stress is to reduce the perimeter of the ring cross section, thereby causing the additional material layer 20 to move radially inward. If the intrinsic stress of the additional material layer 20 is greater than that of the main sensing part 11, the circumferential stress in the additional material layer 20 will exert a significant radial compressive stress on the main sensing part at its outer edge. Figure 13 The example simulation results illustrate this effect by showing that as the width of the ring of the additional material layer 20 increases from zero, the tensile stress at the center of the main sensing element 11 decreases. This effect can be strong enough to give the main sensing element 11 a compressive stress equivalent to a larger ring width.

[0049] Reference Figure 3 As shown, the additional material layer 20 is embedded in the main sensing part 11. At the junction of the edge of the main sensing part 11 and the fixing part 12, the edge of the main sensing part 11 is folded upward to form a folded section. One end of the folded section is connected to the fixing part 12. The surface of the fixing part 12 is roughly flush with the surface of the main sensing part 11. The folded section is higher than the main sensing part 11, thus forming a groove. The additional material layer 20 is embedded in this groove. The additional material layer 20 is limited in the radial direction of the main diaphragm 10. The main sensing part 11 and the additional material layer 20 form an integral structure. Under the action of sound pressure, the main sensing part 11 deforms, and the additional material layer 20 is confined in the groove. At the same time, since the internal stress of the additional material layer 20 is greater than the internal stress of the main sensing part 11, the additional material layer 20 transfers the radial compressive stress to the main sensing part 11, thus avoiding reducing the flexibility of the main sensing part 11.

[0050] like Figures 11 to 13 As shown, under zero applied pressure, the compliance of the main sensing part 11 gradually increases with the increase of the annular width of the additional material layer 20. The radial stress transmitted by the additional material layer 20 to the center of the main sensing part 11 is greater. Under an applied pressure of 50 Pa (or other reasonable pressure values), the compliance of the main sensing part 11 increases slightly with the increase of the width of the additional material layer 20 and tends to stabilize. It can be seen that embedding an additional material layer 20 of a certain width in the main sensing part 11 can significantly improve the robustness of the main diaphragm 10 without affecting the compliance and diaphragm size.

[0051] Reference Figure 4 as well as Figure 5 The additional material layer 20 is stacked on the top or bottom of the main sensing part 11. The additional material layer 20 is not limited in the radial direction of the main diaphragm 10. Under the action of sound pressure, the main sensing part 11 deforms. The radial compressive stress of the additional material layer 20 is transferred to the main sensing part 11 less. Although the additional material layer 20 reduces the tensile stress of the main sensing part 11, the reinforcement effect of the additional material layer 20 stacked on the top or bottom of the main sensing part 11 exceeds this effect.

[0052] like Figures 11 to 12 As shown, under zero applied pressure and under an additional 50 Pa pressure (or other reasonable pressure values), as the width of the additional material layer 20 increases, the compliance of the main sensing part 11 decreases, and the robustness of the main sensing part 11 increases to a certain extent. (Refer to...) Figure 13 As shown, under zero applied pressure, as the annular width of the additional material layer 20 increases, the radial stress transmitted from the additional material layer 20 to the center of the main sensing part 11 gradually decreases.

[0053] Although not shown in the diagram, if the configuration is as follows Figure 4 and 5 As shown. Possibly due to limitations in silicon processing, the inherent tensile stress of the additional material layer 20 is higher than that of the main sensing part 11. If robustness of the additional material layer 20 is required, the strengthening effect can still be reduced.

[0054] Reference Figure 8 As shown, the additional material layer 20 is provided with several through holes 21. When the main diaphragm 10 is subjected to sound pressure, the through holes 21 can form a pressure release path to release the external pressure, thereby further ensuring the flexibility of the main sensing part 11 and improving the sensitivity and mechanical reliability of the MEMS diaphragm.

[0055] In one feasible embodiment, the through hole 21 can be a circular hole. The through holes 21 are divided into several groups, and the multiple through hole groups are spaced apart along the radial direction of the main diaphragm 10. Each through hole group is provided with multiple through holes 21. The multiple through holes 21 in the same through hole group are arranged in a ring with the axis of the main diaphragm 10 as the center line. The inner diameter of the multiple through holes 21 in the same through hole group is the same. The inner diameter of the through holes 21 in adjacent through hole groups is different. Along the radial direction of the main diaphragm 10, the inner diameter of the through holes 21 in adjacent through hole groups increases or decreases in a gradient. Those skilled in the art will know that the inner diameter of the through holes 21 in adjacent through hole groups can also be the same, which is not limited here.

[0056] Reference Figure 9As shown, the additional material layer 20 is provided with a plurality of concentric annular grooves 22. The plurality of annular grooves 22 are arranged sequentially at intervals along the radial direction of the main sensing part 11. When the main diaphragm 10 is subjected to sound pressure, the annular grooves 22 can form a pressure release path to release the external pressure, thereby further ensuring the flexibility of the main sensing part 11 and improving the sensitivity and mechanical reliability of the MEMS diaphragm.

[0057] In one feasible implementation, each annular groove 22 has the same groove width and the spacing between adjacent annular grooves 22 is also the same. The annular groove 22 that is further away from the main sensing part 11 has a larger radius. This can also increase the effective area of ​​the main sensing part 11, increase the capacitance value, and have better acoustic sensing performance.

[0058] Reference Figure 10 As shown, the additional material layer 20 is provided with a plurality of strip grooves 23. The plurality of strip grooves 23 are arranged in a ring with the axis of the main sensing part 11 as the center line. When the main diaphragm 10 is subjected to sound pressure, the strip grooves 23 can form a pressure release path to release the external pressure, thereby further ensuring the flexibility of the main sensing part 11, improving the sensitivity and mechanical reliability of the MEMS diaphragm. By setting the strip grooves 23, the effective area of ​​the main sensing part 11 can also be increased, the capacitance value can be increased, and better acoustic sensing performance can be achieved.

[0059] In one feasible implementation, each strip groove 23 has the same width and the included angle between adjacent strip grooves 23 is the same. The strip groove 23 can be a rectangular structure or a conical structure. When the strip groove 23 is a rectangular structure, the width of the strip groove 23 remains consistent as it extends radially along the main sensing part 11. When the strip groove 23 is a conical structure, the width of the strip groove 23 gradually increases as it extends radially along the main sensing part 11.

[0060] Based on the above embodiments, the present invention also provides a MEMS sensor, which includes the aforementioned MEMS diaphragm. The MEMS diaphragm has an additional material layer 20 disposed on the main diaphragm 10. The additional material layer 20 mechanically reinforces the membrane region experiencing high stress during pressure pulses, and the internal stress of the additional material layer 20 is greater than the internal stress of the main sensing part 11. This ensures the flexibility of the main diaphragm 10, improves the mechanical sensitivity of the MEMS diaphragm, and increases the reliability of the MEMS sensor.

[0061] The above description, based on the embodiments shown in the figures, details the structure, features, and effects of the present invention. The above description is only a preferred embodiment of the present invention, but the present invention is not limited to the scope of implementation shown in the figures. Any changes made in accordance with the concept of the present invention, or equivalent embodiments modified to have equivalent changes, that do not exceed the spirit covered by the specification and figures, should be within the protection scope of the present invention.

Claims

1. A MEMS diaphragm, characterized in that, include: A main diaphragm, the main diaphragm including a main sensing part and a fixing part, wherein a plurality of the fixing parts are circumferentially spaced and connected to the outer edge of the main sensing part; An additional material layer is disposed on the fixing part, or the additional material layer is disposed on the edge of the main sensing part and on the fixing part; The internal stress of the additional material layer is greater than the internal stress of the main sensing part.

2. The MEMS membrane according to claim 1, characterized in that: The additional material layer is embedded within the main sensing part.

3. The MEMS membrane according to claim 1, characterized in that: The additional material is stacked on top of or at the bottom of the main sensing part.

4. The MEMS membrane according to claim 1, characterized in that: The additional material layer has several through holes.

5. The MEMS membrane according to claim 1, characterized in that: The additional material layer is provided with a plurality of concentric annular grooves, which are arranged at intervals along the radial direction of the main sensing part.

6. The MEMS membrane according to claim 1, characterized in that: The additional material layer is provided with a plurality of strip grooves, which are arranged in a ring with the axis of the main sensing part as the center line.

7. The MEMS membrane according to claim 1, characterized in that: The fixing part includes a fixing section and a connecting section. One end of the connecting section is connected to the middle of the fixing section, and the other end of the connecting section is connected to the main sensing part.

8. The MEMS membrane according to claim 7, characterized in that: The connecting segment has arc-shaped notches on both sides.

9. The MEMS membrane according to claim 7, characterized in that: Anchoring parts are provided at both ends of the fixed section.

10. The MEMS membrane according to claim 1, characterized in that: The additional material layer is made of silicon nitride and has a stress of over 100 MPa without a stress gradient, while the main film is made of polycrystalline silicon and has a stress gradient.

11. A MEMS sensor, characterized in that, The MEMS sensor includes the MEMS diaphragm as described in any one of claims 1 to 10.

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