Membrane-based capacitive sensor

Abstract

The application discloses a MEMS capacitive sensor. The MEMS capacitive sensor comprises a substrate, a first electrode, and a second electrode. The substrate has a back cavity penetrating in a thickness direction thereof. The circumferential edge of the first electrode is connected to the substrate through a first anchor layer. The first electrode has a first sub-through hole. The first electrode and the substrate have a first gap therebetween. The circumferential edge of the second electrode is connected to the first electrode through a second anchor layer. The second electrode has a second sub-through hole. The second electrode and the first electrode have a second gap therebetween. The first sub-through hole and the second sub-through hole are communicated to form a first through hole. The first through hole is communicated to the back cavity through the first gap. In the thickness direction, the projection of the first through hole and the projection of the second gap are independent of each other. When the airflow flows through the first through hole, the airflow cannot enter the second gap, so that the accumulation of oil droplets in the second gap and the failure of the capacitive structure can be effectively avoided, and the reliability of the device can be improved.

Description

Technical Field

[0001] This application relates to the field of semiconductor technology, and in particular to a MEMS capacitive sensor. Background Technology

[0002] Devices fabricated based on Micro-Electro-Mechanical Systems (MEMS) are called MEMS devices. MEMS capacitive sensors are one of the important types of MEMS devices, widely used in consumer electronics, automotive electronics, medical devices, and other fields.

[0003] Figure 1 A schematic structural diagram of a prior art MEMS capacitive sensor is shown. (e.g.) Figure 1 As shown, the MEMS capacitive sensor 100 includes: a substrate 110, a first anchor layer 120, a diaphragm 130, a second anchor layer 140, and a back electrode 150. Specifically, the substrate 110 has a back cavity 111 that penetrates the substrate 110 in the thickness direction. The first anchor layer 120 is located between the circumferential edge of the diaphragm 130 and the substrate 110, forming a first gap between the diaphragm 130 and the substrate 110. The second anchor layer is located between the circumferential edge of the back electrode 150 and the circumferential edge of the diaphragm 130, forming a second gap between the back electrode 150 and the diaphragm 130. The back electrode 150 serves as a fixed electrode, and the diaphragm 130 serves as a vibrating electrode. When external pressure is applied to the diaphragm 130, the diaphragm 130 deforms, causing a change in the distance of the second gap in the thickness direction of the substrate 110, thereby causing a change in the capacitance value. To achieve air pressure balance on both sides of the diaphragm 130 when it is not in operation, a plurality of first through holes 131 are formed on the diaphragm 130. To form an airflow channel between the second gap and the outside, a plurality of second through holes 151 are formed on the back electrode plate 150.

[0004] In practical applications, airflow can carry water vapor, tiny particles, or tiny oil droplets. Based on Figure 1 In the MEMS capacitive sensor 100 shown, airflow sequentially flows through the second through-hole 151 and the first through-hole 131 towards the back cavity 111 or flows in the opposite direction. Since the number of first through-holes 131 is much smaller than the number of second through-holes 151, tiny oil droplets in the airflow are more likely to accumulate in and around the first through-hole 131, causing blockage of the second gap near the first through-hole 131, and / or blockage of the first through-hole 131, thus causing the MEMS capacitive sensor 100 to malfunction. Utility Model Content

[0005] In view of the above problems, the purpose of this application is to provide a MEMS capacitive sensor that can prevent device failure caused by oil droplet contamination.

[0006] According to one aspect of the present invention, a MEMS capacitive sensor is provided, comprising: a substrate having a back cavity extending through its thickness direction; a first electrode having a circumferential edge connected to the substrate via a first anchor layer, the first electrode having a first sub-via, and a first gap between the first electrode and the substrate; and a second electrode having a circumferential edge connected to the first electrode via a second anchor layer, the second electrode having a second sub-via, and a second gap between the second electrode and the first electrode, wherein the first sub-via and the second sub-via communicate to form a first through-hole, the first through-hole communicating with the back cavity via the first gap, and the projection of the first through-hole and the projection of the second gap being independent of each other in the thickness direction.

[0007] Optionally, in the thickness direction, the projection of the first through hole falls within the projection range of the back cavity.

[0008] Optionally, one of the first electrode and the second electrode is a vibrating electrode and the other is a fixed electrode. The vibrating electrode has a vibration-sensitive region, and the first through hole is located at the circumferential edge of the vibration-sensitive region. In the thickness direction, the projection of the second gap overlaps with the projection range of the vibration-sensitive region, or the projection of the vibration-sensitive region falls within the projection range of the second gap. The fixed electrode also has a second through hole, and the second gap and the second through hole are connected.

[0009] Optionally, the first electrode is a first vibration electrode, the second electrode is the fixed electrode, the first electrode and the second electrode form a first capacitor, and the MEMS capacitive sensor further includes a third electrode, the third electrode is a second vibration electrode, the third electrode and the second electrode form a second capacitor, wherein the circumferential edge of the third electrode is connected to the second electrode via a third anchor layer, there is a third gap between the third electrode and the second electrode, the third gap, the second through hole and the second gap are connected, in the thickness direction, the projections of the third gap and the second gap at least partially overlap, the third electrode has a third sub-through hole, and the connected first through hole further includes the third sub-through hole.

[0010] Optionally, the second electrode extends along the sidewall of the second sub-through hole to the first electrode, and the third electrode extends along the sidewall of the third sub-through hole to the second electrode.

[0011] Optionally, the third electrode includes: a lower portion connected to the third anchor layer, the lower portion having a release hole, wherein the projection of the release hole in the thickness direction falls within the projection range of the second gap and is independent of the projection of the second through hole, and the release hole is filled by a sealing structure; and an upper portion stacked on top of the lower portion, the upper portion covering the sealing structure and the lower portion.

[0012] Optionally, the lower layer is an insulating layer, and the upper layer is a conductive layer or a composite material layer of a conductive layer and an insulating layer.

[0013] Optionally, the MEMS capacitive sensor further includes a connecting rod that passes through the second through hole, one end of the connecting rod being connected to the first electrode and the other end being connected to the lower layer, wherein the diameter of the connecting rod is smaller than the aperture of the second through hole.

[0014] Optionally, the connecting rod is insulated from the contact surface between the first electrode and the lower portion.

[0015] Optionally, the connecting rod is made of silicon nitride or a multilayer composite material of silicon nitride stacked with polycrystalline silicon and / or amorphous silicon.

[0016] According to the MEMS capacitive sensor disclosed in this application, a first through-hole forms an airflow channel through the MEMS capacitive sensor. Since the projection of the first through-hole and the projection of the second gap are independent of each other in the substrate thickness direction, the airflow will not enter the second gap when flowing through the first through-hole. This effectively avoids the accumulation of oil droplets in the second gap, which could lead to capacitor structure failure and improve device reliability. Attached Figure Description

[0017] The above and other objects, features and advantages of this application will become clearer from the following description of embodiments with reference to the accompanying drawings, in which:

[0018] Figure 1 A schematic structural diagram of a MEMS capacitive sensor in the prior art is shown;

[0019] Figure 2 The diagram shows a schematic structural diagram of a MEMS capacitive sensor in some embodiments of this application;

[0020] Figure 3 Schematic structural diagrams of MEMS capacitive sensors in some embodiments of this application are shown;

[0021] Figure 4 This paper presents schematic structural diagrams of MEMS capacitive sensors in some embodiments of this application. Detailed Implementation

[0022] Various embodiments of the present application will now be described in more detail with reference to the accompanying drawings. In the various drawings, the same elements are indicated by the same or similar reference numerals. For clarity, the various parts in the drawings are not drawn to scale.

[0023] Furthermore, certain terms are used in this specification and claims to refer to specific components. Those skilled in the art will understand that manufacturers may use different names to refer to the same component. This specification and claims do not distinguish components based on differences in name, but rather on differences in function.

[0024] It should be understood that, in the following description, "circuit" may include single or combined hardware circuits, programmable circuits, state machine circuits, and / or elements capable of storing instructions executed by the programmable circuit. When an element or circuit is said to be "connected" to another element or "connected" between two nodes, it may be directly coupled or connected to the other element, or there may be intermediate elements; the connection between elements may be physical, logical, or a combination thereof. Conversely, when an element is said to be "directly coupled to" or "directly connected" to another element, it means that there are no intermediate elements between them.

[0025] Furthermore, it should be noted that in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0026] It should also be noted that in the various methods and processes of this application, the order of the steps does not imply the order of execution, nor does it constitute any limitation on the implementation process of the embodiments of this application.

[0027] This application discloses a MEMS capacitive sensor, comprising a substrate, a first electrode, and a second electrode. The substrate has a back cavity extending through its thickness direction. The circumferential edge of the first electrode is connected to the substrate via a first anchor layer and is suspended above the substrate. A first gap exists between the first electrode and the substrate. The circumferential edge of the second electrode is connected to the first electrode via a second anchor layer and is suspended above the first electrode. A second gap exists between the second electrode and the first electrode. The first electrode has a first sub-through hole, and the second electrode has a second sub-through hole. In the thickness direction, the projections of the first and second sub-through holes at least partially overlap and are independent of the projection of the second gap. The first and second sub-through holes communicate to form a first through hole, which also communicates with the back cavity via the first gap, for balancing the pressure on both sides of the MEMS capacitive sensor in a non-operating state. When the sensor is operating, airflow passes through the first through hole, and oil droplets in the airflow only deposit in or around the first through hole, without entering the second gap. This helps to avoid the influence of oil droplets on the capacitance performance and improves the reliability of the device.

[0028] For ease of understanding this application, Figure 2 Schematic structural diagrams of a MEMS capacitive sensor 200 in some embodiments of this application are shown. Figure 2 As shown, the MEMS capacitive sensor 200 includes a substrate 210, a first electrode 230, and a second electrode 250.

[0029] The substrate 210 has a back cavity 211 extending through the thickness direction. Figure 2 In the accompanying drawings, the first direction is the Z direction shown in the figure, which is the thickness direction of the substrate 210, and the second direction is the X direction shown in the figure, which is the width direction of the substrate 210.

[0030] The circumferential edge of the first electrode 230 is connected to the substrate 210 via the first anchor layer 220 and is suspended above the substrate 210. A first gap 221 exists between the first electrode 230 and the substrate 210. The first electrode 230 also has a first sub-through hole 270a. In the thickness direction Z, the first sub-through hole 270a penetrates the first electrode 230 and connects the first gap 221 and the back cavity 211. Figure 2 In the illustrated embodiment, the first electrode 230 serves as a vibration electrode and has a vibration-sensitive region. For example, this vibration-sensitive region is located in the central region of the first electrode 230, and a first sub-through hole 270a is disposed at the peripheral circumferential edge of the vibration-sensitive region. That is, the first sub-through hole 270a is located on the periphery of the vibration-sensitive region. Figure 2 Specifically, in the width direction X, the vibration-sensitive area is located between the two first sub-through holes 270a. In a preferred embodiment, in the thickness direction Z, the projections of the first sub-through holes 270a and the vibration-sensitive area both fall within the projection range of the back cavity 211.

[0031] The circumferential edge of the second electrode 250 is connected to the first electrode 230 via the second anchor layer 240 and is suspended above the first electrode 230. A second gap 241 exists between the second electrode 250 and the first electrode 230. Figure 2 In this configuration, the second electrode 250 is a fixed electrode, and the second electrode 250 and the vibration-sensitive region of the first electrode 230 form a capacitor. In the thickness direction Z, the projection of the second gap 241 may overlap with the projection of the vibration-sensitive region, or the projection of the vibration-sensitive region may fall within the projection range of the second gap 241.

[0032] The second electrode 250 has a second sub-through hole 270b. In the thickness direction Z, the second sub-through hole 270b penetrates the second electrode 250, and the projection of the second sub-through hole 270b at least partially overlaps with the projection of the first sub-through hole 270a, preferably completely overlapping. The second electrode 250 extends downward along the sidewall of the second sub-through hole 270b to the first electrode 230, connecting the first sub-through hole 270a and the second sub-through hole 270b to form the first through hole 270. In the non-working state, the first through hole 270 connects the back cavity 211 to the outside, achieving pressure balance on both sides and preventing deformation of the first electrode 230 due to pressure difference. The second electrode 250 also has a second through hole 251, which penetrates the second electrode 250 and communicates with the second gap 241. The second through hole 251 can expose the vibration-sensitive area on the first electrode 230.

[0033] In a preferred embodiment, such as Figure 2 As shown, the projection of the first through-hole 270 in the thickness direction Z falls within the projection range of the back cavity 211, ensuring smooth communication between the back cavity 211 and the external airflow through the first through-hole 270 during device operation, effectively reducing the interference of ambient air pressure changes on device performance. Simultaneously, oil droplets carried in the airflow can also directly pass through the first through-hole 270 into the back cavity 211, reducing the risk of oil droplet accumulation.

[0034] When the MEMS capacitive sensor is working, since the airflow only flows through the first through hole 270, the oil droplets carried in the airflow will only accumulate in the first through hole 270 and its surrounding area, without affecting the second through hole 251 and the second gap 241, thus ensuring the long-term stability and sensitivity of the capacitor structure.

[0035] The diameter and number of the first through-hole 270 can be set according to the actual working conditions. For example, in scenarios with heavy oil fumes, the diameter can be increased and the number reduced to improve flow capacity and reduce the risk of blockage; in scenarios with light oil fumes, the diameter can be reduced and the number increased to enhance the uniformity of airflow distribution and the response speed of pressure balance.

[0036] It should be understood that this application does not limit the relative positions of the second anchor layer 240 and the first through hole 270. For example, in some embodiments, the first through hole 270 is disposed adjacent to the second anchor layer 240. In still other embodiments, such as Figure 2 As shown, the first through-hole 270 is located in the second anchor layer 240 and penetrates the second anchor layer 240 in the thickness direction Z. That is, in the thickness direction Z, the projection of the first through-hole 270 falls within the projection range of the second anchor layer 240. Correspondingly, in the width direction X, the second anchor layer 240 is cut into two parts, 240a and 240b, by the first through-hole 270. Among them, 240a is partially surrounded by the first electrode 230 and the second electrode 250, forming an embedded support structure. 240b is located at the circumferential edge of the second gap 241. By adjusting the relative position of the first through-hole 270 and the second anchor layer 240 in the width direction X, the constraint condition of the first electrode 230 can be adjusted, that is, the range of the vibration-sensitive area can be adjusted, thereby adjusting the sensitivity of the MEMS capacitive sensor 200.

[0037] Furthermore, this application does not limit the materials used for each part. For example, the substrate 210 can be silicon, and the first anchor layer 220 and the second anchor layer 240 can be a single material selected from silicon oxide, borosilicate glass, phosphosilicate glass, or borosilicate-phosphosilicate glass, or a composite material of at least two randomly stacked materials. The first electrode 230 can be polycrystalline silicon or amorphous silicon. The second electrode 250 can be a multilayer composite electrode, including a conductive layer and an insulating layer. The conductive layer can be made of polycrystalline silicon or amorphous silicon, and the insulating layer is made of silicon nitride. In particular, the portion of the second electrode 250 extending along the sidewall of the second sub-via 270b can be made of silicon nitride, thereby achieving insulation between the first electrode 230 and the second electrode 250.

[0038] Figure 3 Schematic structural diagrams of MEMS capacitive sensors in some embodiments of this application are shown. For example... Figure 3 As shown, the MEMS capacitive sensor 300 includes a substrate 310, a first electrode 330, and a second electrode 350.

[0039] The substrate 310 has a back cavity 311 that extends through the thickness direction.

[0040] The circumferential edge of the first electrode 330 is connected to the substrate 310 via a first anchor layer 320 and is suspended above the substrate 310. A first gap 321 exists between the first electrode 330 and the substrate 310. The first electrode 330 also has a first sub-via 370a. The circumferential edge of the second electrode 350 is connected to the first electrode 330 via a second anchor layer 340 and is suspended above the first electrode 330. A second gap 341 exists between the second electrode 350 and the first electrode 330. The second electrode 350 also has a second sub-via 370b. The first sub-via 370a and the second sub-via 370b communicate to form a first through-hole 370.

[0041] and Figure 2 The embodiment shown differs from the one described above in that... Figure 3 In this configuration, the first electrode 330 is a fixed electrode, and the second electrode 350 is a vibrating electrode. Therefore, the second through hole is disposed on the first electrode 330. Figure 3 In the middle, the second through hole is marked as 331.

[0042] Figure 4 Schematic structural diagrams of MEMS capacitive sensors in some embodiments of this application are shown. For example... Figure 4 As shown, the MEMS capacitive sensor 400 includes a substrate 410, a first electrode 430, a second electrode 450, and a third electrode 470. The first electrode 430 is a first vibrating electrode, the second electrode 450 is a fixed electrode, and the third electrode 470 is a second vibrating electrode. The first electrode 430 and the second electrode 450 form a first capacitor, and the third electrode 470 and the second electrode 450 form a second capacitor.

[0043] The substrate 410 has a back cavity 411 that extends through the thickness direction.

[0044] The circumferential edge of the first electrode 430 is connected to the substrate 410 via a first anchor layer 420 and is suspended above the substrate 410. A first gap 421 exists between the first electrode 430 and the substrate 410. A first sub-through hole 480a is also provided on the first electrode 430. In the thickness direction Z, the first sub-through hole 480a penetrates the first electrode 430 and connects the first gap 421 and the back cavity 411. Figure 4 In the illustrated embodiment, the first electrode 430 serves as the first vibration electrode, and its vibration-sensitive region can be located in the central region of the first electrode 430. The first sub-through hole 480a is disposed at the peripheral circumferential edge of the vibration-sensitive region. Figure 4 Specifically, in the width direction X, the vibration-sensitive area of ​​the first electrode 430 is located between the two first sub-through holes 480a. In a preferred embodiment, in the thickness direction Z, the projection of the first sub-through hole 480a and the projection of the vibration-sensitive area both fall within the projection range of the back cavity 411.

[0045] The circumferential edge of the second electrode 450 is connected to the first electrode 430 via the second anchor layer 440 and is suspended above the first electrode 430. A second gap 441 exists between the second electrode 450 and the first electrode 430. Figure 4 In this configuration, the second electrode 450 is a fixed electrode, and the second electrode 450 and the vibration-sensitive region of the first electrode 430 form a first capacitor. In the thickness direction Z, the projection of the second gap 441 may overlap with the projection of the vibration-sensitive region of the first electrode 430, or the projection of the vibration-sensitive region of the first electrode 430 may fall within the projection range of the second gap 441.

[0046] The second electrode 450 is provided with a second sub-through hole 480b. In the thickness direction Z, the second sub-through hole 480b penetrates the second electrode 450, and the projection of the second sub-through hole 480b at least partially overlaps with the projection of the first sub-through hole 480a, preferably completely overlapping. The second electrode 450 extends downward along the sidewall of the second sub-through hole 480b to the first electrode 430, so that the first sub-through hole 480a communicates with the second sub-through hole 480b. The second electrode 450 is also provided with a second through hole 451, which penetrates the second electrode 450 and communicates with the second gap 441.

[0047] The circumferential edge of the third electrode 470 is connected to the second electrode 450 via the third anchor layer 460 and is suspended above the second electrode 450. There is a third gap 461 between the second electrode 450 and the third electrode 470.

[0048] A third sub-through hole 480c is provided on the third electrode 470. In the thickness direction Z, the third sub-through hole 480c penetrates the third electrode 470, and the projection of the third sub-through hole 480c at least partially overlaps, preferably completely overlaps, with the projections of the first sub-through hole 480a and the second sub-through hole 480b. The third electrode 470 extends downward along the sidewall of the third sub-through hole 480c to the second electrode 450, so that the third sub-through hole 480c communicates with the second sub-through hole 480b and the first sub-through hole 480a. Figure 4 In the illustrated embodiment, the third electrode 470 serves as the second vibration electrode, and its vibration-sensitive region can be located in the central region of the third electrode 470. The second electrode 450 and the vibration-sensitive region of the third electrode 470 form a second capacitor. In the thickness direction Z, the projections of the vibration-sensitive regions of the first electrode 430 and the third electrode 470 can completely overlap, and the projection of the third gap 461 can completely overlap with the projection of the second gap 441.

[0049] The first sub-through hole 480a, the second sub-through hole 480b, and the third sub-through hole 480c are connected to form the first through hole 480, which is connected to the back cavity 411 through the first gap 421. In the non-working state, the first through hole 480 connects the back cavity 411 to the outside, realizes the air pressure balance on both sides, and avoids the deformation of the capacitor structure due to pressure difference.

[0050] When the MEMS capacitive sensor is working, the airflow will only flow through the first through hole 480, and the oil droplets carried by the airflow will only accumulate in and around the first through hole 480, thus ensuring the long-term stability and sensitivity of the capacitor structure.

[0051] Furthermore, the MEMS capacitive sensor 400 also includes a connecting rod 490. The connecting rod 490 passes through the second through hole 451. One end of the connecting rod 490 is connected to the first electrode 430, and the other end is connected to the third electrode 470. The connecting rod 490 is used to synchronize the movement of the first electrode 430 and the third electrode 470. The connecting rod 490 is made of silicon nitride as a single material or a multilayer composite material of silicon nitride and polycrystalline silicon and / or amorphous silicon randomly stacked. The connecting rod 490 is insulated from the contact surfaces of the first electrode 430 and the third electrode 470. The diameter of the connecting rod 490 is smaller than the aperture of the second through hole 451.

[0052] like Figure 4 As shown, a portion of the third electrode 470 and its extension along the sidewall of the third sub-through hole 480c, the extension of the second electrode 450 along the sidewall of the second sub-through hole 480b, and a portion of the first electrode 430 form a sealed structure. The second gap 441 and the third gap 461 are both located within this sealed structure, which is close to a vacuum. When the MEMS capacitive sensor 400 is operating, airflow cannot enter this sealed structure, effectively preventing oil droplets from being carried into the second and third gaps.

[0053] The MEMS capacitive sensor 400 also includes a release hole 471a. The release hole 471a provides etching paths for the second gap 441 and the third gap 461 during the fabrication process. Correspondingly, after etching, the release hole 471a is filled with a sealing structure 471b. In other words, in the fabricated MEMS capacitive sensor 400, the release hole 471a and the sealing structure 471b are different morphologies of the same location at different fabrication stages.

[0054] like Figure 4 As shown, a release hole 471a is disposed in the lower portion 471 of the third electrode 470. The lower portion 471 is connected to the third anchor layer 460. In the thickness direction, the projection of the release hole 471a falls within the projection range of the second gap 441 and is independent of the projection of the second through hole 451. The third electrode 470 also includes an upper portion 472, which is stacked with the lower portion 471, and the upper portion 472 covers the sealing structure and the lower portion 471. Preferably, the lower portion 471 is an insulating layer, and the lower portion 471 also extends along the sidewall of the third sub-through hole 480c to the second electrode 450. The upper portion 472 is a conductive layer or a composite structure of a conductive layer and an insulating layer. The contact surface between the connecting rod 490 and the third electrode 470 is an insulating material, specifically, the connecting rod 490 is connected to the insulating lower portion 471.

[0055] It should be understood that in actual working conditions, the signal of the first capacitor or the signal of the second capacitor can be acquired separately, that is, the MEMS capacitive sensor operates in single capacitor mode, or the signals of the first capacitor and the second capacitor can be acquired simultaneously, that is, the MEMS capacitive sensor operates in differential mode.

[0056] According to the MEMS capacitive sensor disclosed in this application, a first through-hole forms an airflow channel through the MEMS capacitive sensor. Since the projection of the first through-hole and the projection of the second gap are independent of each other in the substrate thickness direction, the airflow will not enter the second gap when flowing through the first through-hole. This effectively avoids the accumulation of oil droplets in the second gap, which could lead to capacitor structure failure and improve device reliability.

[0057] The embodiments described above, as per the examples of this application, do not exhaustively describe all details, nor do they limit this application to the specific embodiments described above. Clearly, many modifications and variations can be made based on the above description. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of this application, thereby enabling those skilled in the art to effectively utilize this application and its modifications. The scope of protection of this application should be determined by the scope defined in the claims of this application.

Claims

1. A MEMS capacitive sensor, characterized in that, include: The substrate has a back cavity extending through its thickness direction; A first electrode, the circumferential edge of the first electrode being connected to the substrate via a first anchor layer, the first electrode having a first sub-via, and a first gap between the first electrode and the substrate; as well as A second electrode is connected to the first electrode via a second anchor layer at its circumferential edge. The second electrode has a second sub-through hole, and a second gap exists between the second electrode and the first electrode. The first sub-through hole and the second sub-through hole are connected to form a first through hole, which is connected to the back cavity through the first gap. In the thickness direction, the projection of the first through hole and the projection of the second gap are independent of each other.

2. The MEMS capacitive sensor according to claim 1, characterized in that, In the thickness direction, the projection of the first through hole falls within the projection range of the back cavity.

3. The MEMS capacitive sensor according to claim 1, characterized in that, One of the first electrode and the second electrode is a vibrating electrode, and the other is a fixed electrode. The vibrating electrode has a vibration-sensitive region, and the first through hole is located at the circumferential edge of the vibration-sensitive region. In the thickness direction, the projection of the second gap overlaps with the projection range of the vibration-sensitive region, or the projection of the vibration-sensitive region falls within the projection range of the second gap. The fixed electrode also has a second through hole, and the second gap and the second through hole are connected.

4. The MEMS capacitive sensor according to claim 3, characterized in that, The first electrode is a first vibrating electrode, and the second electrode is the fixed electrode. The first electrode and the second electrode form a first capacitor. The MEMS capacitive sensor also includes a third electrode, which is a second vibration electrode. The third electrode and the second electrode form a second capacitor. The third electrode has its circumferential edge connected to the second electrode via a third anchor layer. A third gap exists between the third electrode and the second electrode. The third gap, the second through hole, and the second gap are interconnected. In the thickness direction, the projections of the third gap and the second gap at least partially overlap. The third electrode has a third sub-through hole, and the first through hole connected to it also includes the third sub-through hole.

5. The MEMS capacitive sensor according to claim 4, characterized in that, The second electrode extends along the sidewall of the second sub-through hole to the first electrode, and the third electrode extends along the sidewall of the third sub-through hole to the second electrode.

6. The MEMS capacitive sensor according to claim 4, characterized in that, The third electrode includes: The lower layer, connected to the third anchor layer, is provided with a release hole. In the thickness direction, the projection of the release hole falls within the projection range of the second gap and is independent of the projection of the second through hole. The release hole is filled with a sealing structure. The upper layer is stacked on top of the lower layer, and the upper layer covers the sealing structure and the lower layer.

7. The MEMS capacitive sensor according to claim 6, characterized in that, The lower layer is an insulating layer, and the upper layer is a conductive layer or a composite material layer of a conductive layer and an insulating layer.

8. The MEMS capacitive sensor according to claim 6, characterized in that, The MEMS capacitive sensor also includes: A connecting rod passes through the second through hole, one end of which is connected to the first electrode, and the other end is connected to the lower layer. The diameter of the connecting rod is smaller than the diameter of the second through hole.

9. The MEMS capacitive sensor according to claim 8, characterized in that, The connecting rod is insulated from the contact surface between the first electrode and the lower layer.

10. The MEMS capacitive sensor according to claim 8, characterized in that, The connecting rod is made of silicon nitride or a multilayer composite material consisting of silicon nitride stacked with polycrystalline silicon and / or amorphous silicon.

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