MEMS capacitive sensor and preparation method thereof

Abstract

The invention discloses an MEMS capacitive sensor and a preparation method thereof. The MEMS capacitive sensor comprises a substrate which is provided with a back cavity penetrating in the thickness direction of the substrate; the circumferential edge of the first electrode is connected with the substrate through a first anchor layer, the first electrode is provided with a first sub through hole, and a first gap is formed between the first electrode and the substrate; the circumferential edge of the second electrode is connected with the first electrode through a second anchor layer, the second electrode is provided with a second sub-through hole, a second gap is formed between the second electrode and the first electrode, 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 with the back cavity through the first gap, and in the thickness direction, the thickness of the back cavity is larger than that of the second anchor layer. The projection of the first through hole and the projection of the second gap are mutually independent. When flowing through the first through hole, airflow does not enter the second gap, so that the capacitor structure failure caused by accumulation of oil drops in the second gap 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 and its fabrication method. 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. Summary of the Invention

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

[0006] According to an aspect of the present application, there is provided a MEMS capacitive sensor, comprising: a substrate having a back cavity passing through in a thickness direction thereof; a first electrode having a circumferential edge connected to the substrate via a first anchor layer, the first electrode having a first sub-through hole, and a first gap being formed 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-through hole, and a second gap being formed between the second electrode and the first electrode, wherein 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 via the first gap, and a projection of the first through hole and a projection of the second gap are independent of each other in the thickness direction.

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

[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 vibrating sensitive region, the first through hole is located at a circumferential edge of the vibrating sensitive region, the projection of the second gap and a projection of the vibrating sensitive region overlap, or the projection of the vibrating sensitive region falls within a projection range of the second gap in the thickness direction, and the fixed electrode further has a second through hole, and the second gap and the second through hole are communicated.

[0009] Optionally, the first electrode is a first vibrating 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 comprises a third electrode, the third electrode is a second vibrating electrode, and the third electrode and the second electrode form a second capacitor, wherein a circumferential edge of the third electrode is connected to the second electrode via a third anchor layer, a third gap is formed between the third electrode and the second electrode, the third gap, the second through hole and the second gap are communicated, the projection of the third gap and the projection of the second gap at least partially overlap in the thickness direction, the third electrode has a third sub-through hole, and the communicated first through hole further comprises the third sub-through hole.

[0010] Optionally, the third electrode comprises: a lower portion connected to the third anchor layer, the lower portion being provided with a release hole, a projection of the release hole falls within a projection range of the second gap and is independent of the projection of the second through hole in the thickness direction, and the release hole is filled with a sealing structure; and an upper portion stacked with the lower portion, the upper portion covering the sealing structure and the lower portion.

[0011] Optionally, the MEMS capacitive sensor further comprises a connecting rod, the connecting rod passing through the second through hole, one end of the connecting rod being connected to the first electrode, the other end of the connecting rod being connected to the lower layer, wherein a diameter of the connecting rod is less than a hole diameter of the second through hole.

[0012] According to another aspect of the present application, a method for manufacturing a MEMS capacitive sensor is provided, comprising: providing a substrate; forming a first sacrificial layer on the substrate; forming a first electrode on the first sacrificial layer, the first electrode having a first sub-through hole; forming a second sacrificial layer on the first electrode; forming a second electrode on the second sacrificial layer, the second electrode having a second sub-through hole; forming a back cavity passing through the substrate in a thickness direction; and releasing the sacrificial layers to form a first gap between the first electrode and the substrate, a second gap between the second electrode and the first electrode, the first sacrificial layer connected to a circumferential edge of the first electrode being reserved to form a first anchor layer, the second sacrificial layer connected to a circumferential edge of the second electrode being reserved to form a second anchor layer, wherein after the releasing of the sacrificial layers, the first sub-through hole and the second sub-through hole are communicated to form a first through hole, the first through hole being communicated to the back cavity via the first gap, in the thickness direction, a projection of the first through hole and a projection of the second gap being independent of each other.

[0013] Optionally, in the thickness direction, the projection of the first through hole falls within the projection range of the back cavity.

[0014] Optionally, the second sacrificial layer formed has a fourth sub-through hole, in the thickness direction, a projection of the fourth sub-through hole is adjacent to and surrounds an outer periphery of a projection of the first sub-through hole, the step of forming the second electrode comprises: depositing a material layer of the second electrode, the material layer of the second electrode filling the fourth sub-through hole and covering the second sacrificial layer; patterning the material layer to form the second sub-through hole, the second sub-through hole exposing the second sacrificial layer, wherein in the thickness direction, the projection of the second sub-through hole overlaps the projection of the first sub-through hole, the exposed second sacrificial layer filling and exceeding the first sub-through hole.

[0015] Optionally, the second sacrificial layer formed has a fourth sub-via hole, a projection of the first sub-via hole falls within a projection range of the fourth sub-via hole in the thickness direction, and the step of forming the second electrode includes: depositing a material layer of the second electrode, the material layer of the second electrode filling the fourth sub-via hole and covering the second sacrificial layer; and patterning the material layer to form the second sub-via hole, the second sub-via hole exposing the second sacrificial layer, wherein a projection of the second sub-via hole overlaps with a projection of the first sub-via hole in the thickness direction, and the exposed second sacrificial layer is located in the first sub-via hole.

[0016] 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, the first via hole is located at a circumferential edge of the vibration sensitive region, a projection of the second gap overlaps with a projection range of the vibration sensitive region or the projection of the vibration sensitive region falls within the projection range of the second gap in the thickness direction, and the preparation method further includes: forming a second via hole on the fixed electrode, the second gap and the second via hole being communicated.

[0017] Optionally, the first electrode is a first vibrating electrode, the second electrode is the fixed electrode, and the first electrode and the second electrode form a first capacitor, after the second electrode is formed, the preparation method further includes: forming a third sacrificial layer on the second electrode; and forming a third electrode on the third sacrificial layer, the third electrode having a third sub-via hole, wherein, after the sacrificial layer is released, a third gap is formed between the second electrode and the third electrode, a projection of the third gap at least partially overlaps with a projection of the second gap in the thickness direction, the third sacrificial layer connected to a circumferential edge of the third electrode is reserved to form a third anchor layer, and the communicated first via hole further includes the third sub-via hole.

[0018] Optionally, the third sacrificial layer formed has a fifth sub-via hole, a projection of the fifth sub-via hole is adjacent to a projection of the first sub-via hole and surrounds an outer periphery of the first sub-via hole in the thickness direction, and the step of forming the third electrode includes: depositing a lower layer material of the third electrode, the lower layer material filling the fifth sub-via hole and covering the third sacrificial layer; depositing an upper layer material of the third electrode, the upper layer material covering the lower layer material; and patterning the upper layer material and the lower layer material to form the third sub-via hole, a projection of the third sub-via hole overlaps with a projection of the first sub-via hole in the thickness direction, and the third sacrificial layer exposed by the third sub-via hole fills and exceeds the second sub-via hole.

[0019] Optionally, the third sacrificial layer formed has a fifth sub-via hole, in the thickness direction, a projection of the first sub-via hole falls within a projection range of the fifth sub-via hole, the step of forming the third electrode comprises: depositing a lower layer material of the third electrode, the lower layer material fills the fifth sub-via hole and covers the third sacrificial layer; depositing an upper layer material of the third electrode, the upper layer material covers the lower layer material; and patterning the upper layer material and the lower layer material to form the third sub-via hole, in the thickness direction, a projection of the third sub-via hole and a projection of the first sub-via hole overlap, and the third sacrificial layer exposed by the third sub-via hole is located in the second sub-via hole.

[0020] Optionally, before depositing the lower layer material, the preparation method further comprises: forming a connecting rod, the connecting rod passes through the second via hole and connects the first electrode, a diameter of the connecting rod is smaller than a hole diameter of the second via hole, and after depositing the lower layer material, the connecting rod also connects the lower layer material.

[0021] Optionally, between depositing the lower layer material and depositing the upper layer material, the preparation method further comprises: patterning the lower layer material to form a release hole, in the thickness direction, a projection of the release hole falls within a projection range of the second gap and is independent of a projection of the second via hole; and forming a hole sealing structure filling the release hole.

[0022] Optionally, the step of forming the hole sealing structure filling the release hole comprises: depositing a film layer material, the film layer material fills the release hole and covers the lower layer material; and removing the film layer material on a surface of the lower layer material, the film layer material remaining in the release hole forms the hole sealing structure, wherein, in the case that the projection of the first sub-via hole falls within the projection range of the fifth sub-via hole, a surface of the deposited lower layer material has a groove, and the deposited film layer material also fills the groove.

[0023] Optionally, the release sacrificial layer comprises: between forming the release hole and forming the hole sealing structure, removing part of the third sacrificial layer and the second sacrificial layer through the release hole to form the second gap and the third gap; and after forming the back cavity, removing part of the first sacrificial layer to form the first gap, and removing the second sacrificial layer and the third sacrificial layer in the first via hole.

[0024] According to the MEMS capacitive sensor and the preparation method thereof disclosed in the present application, the first through hole penetrates the MEMS capacitive sensor to form an airflow channel. Since the projection of the first through hole and the projection of the second gap are independent of each other in the thickness direction of the substrate, when the airflow flows through the first through hole, the airflow will not enter the second gap, which can effectively avoid the accumulation of oil droplets in the second gap and cause the failure of the capacitive structure, thereby improving the reliability of the device. BRIEF DESCRIPTION OF DRAWINGS

[0025] The above and other objects, features and advantages of the present application will become more apparent from the following description when taken in conjunction with the accompanying drawings, in which:

[0026] Figure 1 A schematic structural diagram of a MEMS capacitive sensor in the prior art is shown;

[0027] Figure 2 A schematic structural diagram of a MEMS capacitive sensor in some embodiments of the present application is shown;

[0028] Figure 3 A schematic structural diagram of a MEMS capacitive sensor in some other embodiments of the present application is shown;

[0029] Figure 4 A schematic structural diagram of a MEMS capacitive sensor in some other embodiments of the present application is shown;

[0030] Figure 5 A schematic flow diagram of a preparation method of a MEMS capacitive sensor in the present application is shown;

[0031] Figures 6A-6E A schematic sectional view of each stage of a preparation method of a MEMS capacitive sensor in some embodiments of the present application is shown;

[0032] Figures 7A-7F A schematic sectional view of each stage of a preparation method of a MEMS capacitive sensor in some other embodiments of the present application is shown. DETAILED DESCRIPTION

[0033] Various embodiments of the present application will be described in detail with reference to the drawings, below. In each of the drawings, the same elements are denoted by the same or similar reference numerals to indicate the same or similar elements. For the sake of clarity, each portion in the drawings is not drawn to scale.

[0034] Meanwhile, certain terms have been used throughout this application in describing particular embodiments. Those of ordinary skill in the art will recognize that different names can be used to refer to the same component. Regardless of the terminology used, the description in this application should not be construed to limit the scope of the disclosure to only the explicitly described components. Instead, the description should be understood to encompass the components defined by the language of the claims.

[0035] It should be understood that, in the following description, "circuitry" can include a single or multiple components of hardware, programmable circuitry, state machine circuitry, and / or elements storing instructions for execution by programmable circuitry. When an element or circuitry is referred to as being "connected to" another element or "between" two nodes, it can be directly coupled or connected to the other element or there can be intervening elements between the elements, the connection between elements can be physical, logical, or a combination thereof. In contrast, when an element is referred to as being "directly coupled to" or "directly connected to" another element, it implies that there are no intervening elements between the two.

[0036] In addition, it should also be noted that, in this document, the relationship terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between the entities or operations. Moreover, the terms "include", "contain" or any other variant thereof are intended to cover non-exclusive inclusion, so that the process, method, article or device including a series of elements not only includes those elements, but also includes other elements not explicitly listed or inherent to such process, method, article or device. Without more limitations, the element defined by the statement "including a" does not exclude the presence of additional identical elements in the process, method, article or device including the element.

[0037] It should also be noted that in the methods and processes of the present application, the size of the step number does not mean the order of execution, nor does it constitute any limitation on the implementation process of the embodiments of the present application.

[0038] The present application discloses a MEMS capacitive sensor, which comprises a substrate, a first electrode and a second electrode. The substrate has a back cavity through it in the thickness direction. The circumferential edge of the first electrode is connected to the substrate through a first anchor layer and is suspended above the substrate. There is a first gap between the first electrode and the substrate. The circumferential edge of the second electrode is connected to the first electrode through a second anchor layer and is suspended above the first electrode, and there is a second gap between the second electrode and the first electrode. The first electrode has a first sub-via hole, and the second electrode has a second sub-via hole. In the thickness direction, the projection of the first sub-via hole and the projection of the second sub-via hole at least partially overlap and are independent of the projection of the second gap. The first sub-via hole and the second sub-via hole are connected to form a first via hole, and the first via hole is also connected to the back cavity through the first gap, for balancing the pressure on both sides of the MEMS capacitive sensor in the non-working state. When the sensor is working, the airflow flows through the first via hole, and the oil droplets in the airflow will only deposit in the first via hole or around it, and will not enter the second gap, which is conducive to avoiding the influence of oil droplets on the capacitance performance and improving the reliability of the device.

[0039] For the purpose of facilitating understanding of the present application, Figure 2 A schematic structural diagram of the MEMS capacitive sensor 200 in some embodiments of the present application is shown. As shown, the MEMS capacitive sensor 200 comprises a substrate 210, a first electrode 230 and a second electrode 250. Figure 2

[0040] The substrate 210 has a back cavity 211 through in the thickness direction. In Figure 2 In the drawings and subsequent drawings, the first direction is the Z direction shown, i.e. the thickness direction of the substrate 210, and the second direction is the X direction shown, i.e. the width direction of the substrate 210.

[0041] The circumferential edge of the first electrode 230 is connected to the substrate 210 through the first anchor layer 220 and suspended above the substrate 210, and the first electrode 230 has a first gap 221 with the substrate 210. The first electrode 230 is also provided with a first sub-via hole 270a. In the thickness direction Z, the first sub-via hole 270a penetrates the first electrode 230 and communicates the first gap 221 and the back cavity 211. In Figure 2 In the embodiment shown, the first electrode 230 serves as a vibration electrode and has a vibration sensitive region. For example, the vibration sensitive region is located in the central region of the first electrode 230, and the first sub-via hole 270a is arranged at the peripheral circumferential edge of the vibration sensitive region. That is, the first sub-via hole 270a is located at the periphery of the vibration sensitive region. In Figure 2 In particular, in the width direction X, the vibration sensitive region is located between the two first sub-via holes 270a. In a preferred embodiment, in the thickness direction Z, the projection of the first sub-via hole 270a and the projection of the vibration sensitive region both fall within the projection range of the back cavity 211.

[0042] The circumferential edge of the second electrode 250 is connected to the first electrode 230 through the second anchor layer 240 and suspended above the first electrode 230, and the second electrode 250 has a second gap 241 with the first electrode 230. In Figure 2 In particular, the second electrode 250 is a fixed electrode, and the second electrode 250 forms a capacitance with the vibration sensitive region of the first electrode 230. In the thickness direction Z, the projection of the second gap 241 can overlap the projection of the vibration sensitive region, or the projection of the vibration sensitive region falls within the projection range of the second gap 241.

[0043] ​The second electrode 250 is provided with a second sub-hole 270b. In the thickness direction Z, the second sub-hole 270b penetrates the second electrode 250, and the projection of the second sub-hole 270b at least partially overlaps, preferably completely overlaps, the projection of the first sub-hole 270a. The second electrode 250 extends downward along the side wall of the second sub-hole 270b to the first electrode 230, so that the first sub-hole 270a and the second sub-hole 270b are in communication to form a first hole 270. The first hole 270 is in communication with the outside in the non-working state, so as to balance the air pressure on both sides and avoid deformation of the first electrode 230 due to pressure difference. The second electrode 250 is also provided with a second hole 251, which penetrates the second electrode 250 and is in communication with the second gap 241. The second hole 251 can expose the vibration-sensitive area on the first electrode 230.

[0044] In a preferred embodiment, as shown in Figure 2 The projection of the first hole 270 in the thickness direction Z falls within the projection range of the back cavity 211, ensuring that the back cavity 211 is in smooth communication with the outside airflow through the first hole 270 during device operation, effectively reducing the interference of environmental air pressure changes on device performance. At the same time, oil droplets carried in the airflow can also directly pass through the first hole 270 into the back cavity 211, reducing the risk of oil droplet accumulation.

[0045] When the MEMS capacitive sensor is working, since the airflow only flows through the first hole 270, the oil droplets carried in the airflow will only accumulate around the first hole 270, and will not affect the second hole 251 and the second gap 241, thereby ensuring the long-term stability and sensitivity of the capacitive structure.

[0046] The aperture and number of the first hole 270 can be set according to the actual working condition. For example, in a heavy oil smoke scene, the aperture can be increased and the number can be reduced to improve the flow capacity and reduce the risk of blockage; in a light oil smoke scene, the aperture can be reduced and the number can be increased to enhance the uniformity of airflow distribution and the response speed of pressure balance.

[0047] It should be understood that the present application does not limit the relative position of the second anchor layer 240 and the first hole 270. For example, in some embodiments, the first hole 270 is provided adjacent to the second anchor layer 240. In yet other embodiments, as shown in Figure 2As 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.

[0048] 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.

[0049] 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.

[0050] The substrate 310 has a back cavity 311 that extends through the thickness direction.

[0051] 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.

[0052] and Figure 2 The embodiment shown differs from the one described above in that... Figure 3In the embodiment shown in FIG. 3, the first electrode 330 is a fixed electrode, and the second electrode 350 is a vibrating electrode. Therefore, the second through-hole is arranged on the first electrode 330, and the first through-hole is arranged on the second electrode 350. Figure 3 In the embodiment shown in FIG. 3, the first electrode 330 is a fixed electrode, and the second electrode 350 is a vibrating electrode. Therefore, the second through-hole is arranged on the first electrode 330, and the first through-hole is arranged on the second electrode 350.

[0053] Figure 4 A schematic structural diagram of a MEMS capacitive sensor in yet another embodiment of the present application is shown. As shown in FIG. 4, 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. Figure 4

[0054] The substrate 410 has a back cavity 411 that penetrates through in the thickness direction Z.

[0055] The circumferential edge of the first electrode 430 is connected to the substrate 410 through the first anchor layer 420 and is suspended above the substrate 410, and the first electrode 430 has a first gap 421 with the substrate 410. The first electrode 430 is further provided with a first sub-through-hole 480a. In the thickness direction Z, the first sub-through-hole 480a penetrates through the first electrode 430 and communicates the first gap 421 and the back cavity 411. In the embodiment shown in FIG. 4, the first electrode 430 is a first vibrating electrode, and its vibrating sensitive region can be a central region of the first electrode 430. The first sub-through-hole 480a is arranged at the peripheral circumferential edge of the vibrating sensitive region. Figure 4 Figure 4 In the embodiment shown in FIG. 4, the first electrode 430 is a first vibrating electrode, and its vibrating sensitive region can be a central region of the first electrode 430. The first sub-through-hole 480a is arranged at the peripheral circumferential edge of the vibrating sensitive region.

[0056] The circumferential edge of the second electrode 450 is connected to the first electrode 430 through the second anchor layer 440 and is suspended above the first electrode 430, and the second electrode 450 has a second gap 441 with the first electrode 430. In the embodiment shown in FIG. 4, the second electrode 450 is a fixed electrode, and the second electrode 450 forms a first capacitor with the vibrating sensitive region of the first electrode 430. In the thickness direction Z, the projection of the second gap 441 can overlap the projection of the vibrating sensitive region of the first electrode 430, or the projection of the vibrating sensitive region of the first electrode 430 falls within the projection range of the second gap 441. Figure 4

[0057] ​​​The second electrode 450 is provided with a second sub-via hole 480b. In the thickness direction Z, the second sub-via hole 480b penetrates the second electrode 450, and a projection of the second sub-via hole 480b at least partially overlaps, preferably completely overlaps, a projection of the first sub-via hole 480a. The second electrode 450 extends downward along a side wall of the second sub-via hole 480b to the first electrode 430, so that the first sub-via hole 480a and the second sub-via hole 480b are in communication. The second electrode 450 is further provided with a second via hole 451, which penetrates the second electrode 450 and is in communication with the second gap 441.

[0058] The circumferential edge of the third electrode 470 is connected to the second electrode 450 through the third anchor layer 460, and is suspended above the second electrode 450, with a third gap 461 between the second electrode 450 and the third electrode 470.

[0059] The third electrode 470 is provided with a third sub-via hole 480c. In the thickness direction Z, the third sub-via hole 480c penetrates the third electrode 470, and a projection of the third sub-via hole 480c at least partially overlaps, preferably completely overlaps, an overlapping region of projections of the first sub-via hole 480a and the second sub-via hole 480b. The third electrode 470 extends downward along a side wall of the third sub-via hole 480c to the second electrode 450, so that the third sub-via hole 480c, the second sub-via hole 480b, and the first sub-via hole 480a are in communication. In Figure 4 In the illustrated embodiment, the third electrode 470 serves as a second vibration electrode, and its vibration-sensitive region can be located in a central region of the third electrode 470. The vibration-sensitive regions of the second electrode 450 and the third electrode 470 form a second capacitor. In the thickness direction Z, a projection of the vibration-sensitive region of the first electrode 430 and a projection of the vibration-sensitive region of the third electrode 470 can completely overlap, and a projection of the third gap 461 and a projection of the second gap 441 can completely overlap.

[0060] The first sub-via hole 480a, the second sub-via hole 480b, and the third sub-via hole 480c form a first via hole 480, which is in communication with the back cavity 411 through the first gap 421. In a non-working state, the first via hole 480 allows the back cavity 411 to communicate with the outside, achieving pressure balance on both sides and avoiding deformation of the capacitor structure due to pressure difference.

[0061] When the MEMS capacitive sensor is in operation, the airflow only flows through the first via hole 480, and the oil droplets carried in the airflow only accumulate around the first via hole 480, thereby ensuring the long-term stability and sensitivity of the capacitor structure.

[0062] Further, the MEMS capacitive sensor 400 further comprises 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 of the connecting rod 490 is connected to the third electrode 470, and the connecting rod 490 is used to synchronize the movement of the first electrode 430 and the third electrode 470. The material of the connecting rod 490 is a single material of silicon nitride or a multi-layer composite material randomly stacked by silicon nitride, polysilicon or / and amorphous silicon. The contact surface of the connecting rod 490 and the first electrode 430 and the third electrode 470 is insulated. The diameter of the connecting rod 490 is smaller than the hole diameter of the second through-hole 451.

[0063] As shown in FIG. 4, the third electrode 470 is partially exposed to the second gap 441 and the third gap 461. The third electrode 470 is partially exposed to the second gap 441 through the second sub-through-hole 480b. The third electrode 470 is partially exposed to the third gap 461 through the third sub-through-hole 480c. Figure 4 As shown in FIG. 4, the third electrode 470 is partially exposed to the second gap 441 and the third gap 461. The third electrode 470 is partially exposed to the second gap 441 through the second sub-through-hole 480b. The third electrode 470 is partially exposed to the third gap 461 through the third sub-through-hole 480c.

[0064] The MEMS capacitive sensor 400 further comprises a release hole 471a. The release hole 471a is used to provide an etching path of the second gap 441 and the third gap 461 during the preparation process. Accordingly, after etching, the release hole 471a is filled by the hole sealing structure 471b. That is, in the prepared MEMS capacitive sensor 400, the release hole 471a and the hole sealing structure 471b are different manifestations of the same position at different preparation stages.

[0065] As shown in FIG. 4, the third electrode 470 is partially exposed to the second gap 441 and the third gap 461. The third electrode 470 is partially exposed to the second gap 441 through the second sub-through-hole 480b. The third electrode 470 is partially exposed to the third gap 461 through the third sub-through-hole 480c. Figure 4 As shown in FIG. 4, the release hole 471a is arranged 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 further comprises an upper portion 472, which is arranged in a stacked manner with the lower portion 471, and the upper portion 472 covers the hole sealing structure and the lower portion 471. Preferably, the lower portion 471 is an insulating layer, and the lower portion 471 further 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 of the connecting rod 490 and the third electrode 470 is an insulating material, which can be specifically referred to as the connection of the connecting rod 490 and the insulating lower portion 471.

[0066] It should be understood that in actual working conditions, the signal of the first capacitor or the signal of the second capacitor can be collected alone, that is, the MEMS capacitive sensor works in a single-capacitor mode, or the signal of the first capacitor and the signal of the second capacitor can be collected simultaneously, that is, the MEMS capacitive sensor works in a differential mode.

[0067] According to the MEMS capacitive sensor disclosed in the present application, the first through hole forms an air flow 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 thickness direction of the substrate, when the air flow flows through the first through hole, it will not enter the second gap, which can effectively avoid the accumulation of oil droplets in the second gap and cause the failure of the capacitive structure, thereby improving the reliability of the device.

[0068] The present application also discloses a manufacturing method of a MEMS capacitive sensor, which can be used to manufacture the MEMS capacitive sensor structure of any of the above embodiments. As shown in the figure, the method comprises the following steps: Figure 5

[0069] Step S11, providing a substrate;

[0070] Step S12, forming a first sacrificial layer on the substrate;

[0071] Step S13, forming a first electrode on the first sacrificial layer, the first electrode having a first sub-through hole;

[0072] Step S14, forming a second sacrificial layer on the first electrode;

[0073] Step S15, forming a second electrode on the second sacrificial layer, the second electrode having a second sub-through hole;

[0074] Step S16, forming a back cavity penetrating through the substrate in the thickness direction; and

[0075] Step S17, releasing the sacrificial layer to form a first gap between the first electrode and the substrate, a second gap between the second electrode and the first electrode, the first sacrificial layer connected to the circumferential edge of the first electrode is reserved to form a first anchor layer, and the second sacrificial layer connected to the circumferential edge of the second electrode is reserved to form a second anchor layer. After releasing the sacrificial layer, 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 with the back cavity through the first gap, and in the thickness direction, the projection of the first through hole and the projection of the second gap are independent of each other.

[0076] ​According to the preparation method of the MEMS capacitive sensor disclosed in the present application, the first through hole penetrates the MEMS capacitive sensor to form an airflow channel. Since the projection of the first through hole and the projection of the second gap are independent of each other in the thickness direction of the substrate, when the airflow flows through the first through hole, it will not enter the second gap, which can effectively avoid the accumulation of oil droplets in the second gap and cause the failure of the capacitive structure, thereby improving the reliability of the device.

[0077] In order to facilitate the understanding of the preparation method disclosed in the present application, Figures 6A-6E In some embodiments, the schematic cross-sectional views of each stage of the preparation method of the MEMS capacitive sensor according to the present application are shown. Specifically, in Figures 6A-6E Specifically, the preparation of the MEMS capacitive sensor 200 as shown Figure 2 is taken as an example, the preparation method disclosed in the present application will be described in detail below in combination with Figures 6A-6E .

[0078] As shown in Figure 6A , the substrate 210 provided in step S11 is, for example, a silicon substrate. The first sacrificial layer 220 formed in step S12 covers the substrate 210, and the first sacrificial layer 220 is, for example, a single material in silicon oxide, borosilicate glass, phosphosilicate glass or borophosphosilicate glass, or at least two randomly stacked composite materials. The first electrode 230 formed in step S13 has a first sub-through hole 270a. The first electrode 230 is, for example, polycrystalline silicon or amorphous silicon. The first sub-through hole 270a penetrates the first electrode 230 in the thickness direction Z. In Figure 6A the embodiment shown, the first electrode 230 serves as a vibrating electrode in the formed capacitive sensor, and the vibration sensitive region thereof can be located at the central region of the first electrode 230, and the first sub-through hole 270a is arranged at the peripheral edge of the vibration sensitive region. In Figure 6A , the vibration sensitive region of the first electrode 230 is located between the two first sub-through holes 270a in the width direction X.

[0079] In combination with Figure 6A and Figure 6B , in step S14, the second sacrificial layer 240 is formed on the first electrode 230 and covers the first sub-through hole 270a. The second sacrificial layer 240 is, for example, a single material in silicon oxide, borosilicate glass, phosphosilicate glass or borophosphosilicate glass, or at least two randomly stacked composite materials. The second sacrificial layer 240 has a fourth sub-through hole 240a. In some embodiments, as shown in Figure 6B (a) of FIG. 1, the projection of the fourth sub-through hole 240a and the projection of the first sub-through hole 270a are adjacent and surround the outer periphery of the first sub-through hole 270a in the thickness direction Z. In still other embodiments, as shown in Figure 6BAs shown in Figure (b), in the thickness direction Z, the projection of the first sub-through hole 270a falls within the projection range of the fourth sub-through hole 240a. In the following text, the two are taken as concentric projections as an example.

[0080] like Figure 6C and Figure 6D As shown, in step S15, the second electrode 250 is formed on the second sacrificial layer 240. Specifically, the material layer of the second electrode is first deposited, and then the material layer of the second electrode is patterned to obtain the second electrode 250.

[0081] Furthermore, when the fourth sub-hole 240a has a different shape, the structural morphology of the second electrode 250 changes accordingly. Figure 6C and Figure 6D Figure (a) corresponds to the projection of the fourth sub-through hole 240a being adjacent to and surrounding the projection of the first sub-through hole 270a, while Figure (b) corresponds to the case of concentric projection.

[0082] Combination Figures 6B-6D In each of Figures (a), when the projection of the fourth sub-via 240a is adjacent to and surrounds the projection of the first sub-via 270a, step S15 specifically includes: depositing a material layer for the second electrode. The material layer of the second electrode can be a multilayer composite material, 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 insulating layer can be deposited first to at least fill the fourth sub-via 240a, and then the remaining portion of the composite material can be deposited to achieve insulation between the first electrode 230 and the second electrode 250. The material layer of the second electrode also covers the second sacrificial layer 240. In a preferred embodiment, the surface of the material layer of the second electrode is planarized after deposition. A patterning process is then performed to form the second sub-via 270b. In the thickness direction Z, the projection of the second sub-via 270b at least partially overlaps with the projection of the first sub-via 270a, preferably completely overlaps. The material layer of the second electrode deposited in the fourth sub-via 240a is retained during the patterning process, such that the material layer of the second electrode extends along the sidewall of the second sub-via 270b to the first electrode 230. The second sacrificial layer 240 exposed by the second sub-via 270b fills the first sub-via 270a and extends beyond the first sub-via 270a.

[0083] because Figures 6A-6E The embodiments correspond to Figure 2The illustrated MEMS capacitive sensor 200, therefore, also forms a second via 251 in step S15. The second via 251 penetrates the second electrode 250 and exposes the second sacrificial layer 240. In the thickness direction Z, the projection of the second via 251 falls within the projected range of the vibration-sensitive area of the first electrode 230. After subsequent release of the second sacrificial layer 240, the second via 251 exposes the vibration-sensitive area of the first electrode 230.

[0084] In combination with Figures 6B-6D In the case of the fourth sub-via 240a and the first sub-via 270a being concentric projections, step S15 specifically comprises depositing a material layer of the second electrode. The material layer of the second electrode can be a multi-layer composite material, which includes a conductive layer and an insulating layer. The conductive layer can be polysilicon or amorphous silicon, and the insulating layer can be silicon nitride. In particular, the insulating layer can be deposited to at least fill the fourth sub-via 240a, and the remaining part of the composite material can be deposited to achieve insulation between the first electrode 230 and the second electrode 250. The material layer of the second electrode also covers the second sacrificial layer 240. It should be understood that, as in Figure 6C In the case of the fourth sub-via 240a and the first sub-via 270a being concentric projections, step S15 specifically comprises depositing a material layer of the second electrode. The material layer of the second electrode can be a multi-layer composite material, which includes a conductive layer and an insulating layer. The conductive layer can be polysilicon or amorphous silicon, and the insulating layer can be silicon nitride. In particular, the insulating layer can be deposited to at least fill the fourth sub-via 240a, and the remaining part of the composite material can be deposited to achieve insulation between the first electrode 230 and the second electrode 250. The material layer of the second electrode also covers the second sacrificial layer 240. It should be understood that, as in

[0085] In the case of the fourth sub-via 240a and the first sub-via 270a being concentric projections, step S15 specifically comprises depositing a material layer of the second electrode. The material layer of the second electrode can be a multi-layer composite material, which includes a conductive layer and an insulating layer. The conductive layer can be polysilicon or amorphous silicon, and the insulating layer can be silicon nitride. In particular, the insulating layer can be deposited to at least fill the fourth sub-via 240a, and the remaining part of the composite material can be deposited to achieve insulation between the first electrode 230 and the second electrode 250. The material layer of the second electrode also covers the second sacrificial layer 240. It should be understood that, as in Figures 6A-6E Figure 2 The illustrated MEMS capacitive sensor 200, therefore, also forms a second via 251 in step S15. The second via 251 penetrates the second electrode 250 and exposes the second sacrificial layer 240. In the thickness direction Z, the projection of the second via 251 falls within the projected range of the vibration-sensitive area of the first electrode 230. After subsequent release of the second sacrificial layer 240, the second via 251 exposes the vibration-sensitive area of the first electrode 230.

[0086] As in Figure 6E ​As shown, the (a) figure corresponds to the case where the projection of the fourth sub-via hole 240a is adjacent to and surrounds the outer periphery of the projection of the first sub-via hole 270a, and the (b) figure corresponds to the case where the projection of the fourth sub-via hole 240a is concentric with the projection of the first sub-via hole 270a. In both cases, the projection of the first sub-via hole 270a and the projection of the vibration sensitive region both fall within the projection range of the back cavity 211 in the thickness direction Z.

[0087] It should be understood that, for the case where the first electrode is a fixed electrode and the second electrode is a vibrating electrode, the above-mentioned preparation method is also applicable to forming a MEMS capacitive sensor structure as shown in FIG. 4. Figures 6B-6E In the two cases corresponding to the (a) figure and the (b) figure in FIG. 2, after releasing the first sacrificial layer 220 and the second sacrificial layer 240 in step S17, a first gap 221 can be formed between the first electrode 230 and the substrate 210, and a second gap 241 can be formed between the second electrode 250 and the first electrode 230. Figure 2 As shown, the MEMS capacitive sensor structure 200 is formed.

[0088] Specifically, the portion of the first sacrificial layer 220 between the first electrode 230 and the substrate 210 is removed to form the first gap 221, and the portion of the second sacrificial layer 240 between the second electrode 250 and the first electrode 230 is removed to form the second gap 241. In the thickness direction Z, the projection of the vibration sensitive region of the first electrode 230 overlaps with the projection range of the second gap 241, or the projection of the vibration sensitive region falls within the projection range of the second gap 241.

[0089] The first sacrificial layer 220 connected to the circumferential edge of the first electrode 230 is retained to form a first anchor layer, and the second sacrificial layer 240 connected to the circumferential edge of the second electrode is retained to form a second anchor layer. After releasing the sacrificial layer, the first sub-via hole 270a and the second sub-via hole 270b are connected to form a first via hole 270, and the first via hole 270 is connected to the back cavity 211 through the first gap 221. In the thickness direction, the projection of the first via hole 270 and the projection of the second gap 241 are independent of each other.

[0090] It should be understood that, in yet other embodiments, for the case where the first electrode is a fixed electrode and the second electrode is a vibrating electrode, the above-mentioned second via hole can be formed when the first electrode is formed. Accordingly, after releasing the sacrificial layer, the second via hole exposes the vibration sensitive region on the second electrode.

[0091] In yet other embodiments, the above-mentioned preparation method is also applicable to forming a MEMS capacitive sensor structure as shown in FIG. 4. Figure 4 As shown, the MEMS capacitive sensor structure 400 is formed. Figures 6A-6D The steps of forming the second electrode and before can refer to the description of the above-mentioned MEMS capacitive sensor structure 200, and will not be described here. Between the formation of the second electrode and the formation of the back cavity, the corresponding preparation method further comprises: forming a third sacrificial layer on the second electrode; forming a third electrode on the third sacrificial layer, the third electrode having a third sub-via hole. For ease of understanding,Figures 7A-7F The schematic cross-sectional views of the added stages are shown.

[0092] In the preparation of the MEMS capacitive sensor 400 as shown, Figure 4 after the formation of the second electrode 450, a third sacrificial layer 460 is deposited. As shown, Figure 7A The third sacrificial layer 460, the second electrode 450, the second sacrificial layer 440, the first electrode 430, the first sacrificial layer 420 and the substrate 410 are stacked.

[0093] As shown, Figure 7B The third sacrificial layer 460 is patterned to form a fifth sub-via 460a. Similarly, the projection of the fifth sub-via 460a can be contiguous to and surround the outer periphery of the projection of the first sub-via 480a, i.e. as shown in (a) of FIG. 4B; or the projection of the first sub-via 480a can fall within the projection of the fifth sub-via 460a, e.g. as a concentric projection, i.e. as shown in (b) of FIG. 4B. Figure 7B Figure 7B

[0094] Further, in the patterning of the third sacrificial layer 460, a sixth sub-via 460b is also formed. The sixth sub-via 460b passes through the second via 451 and exposes the first electrode 430. The aperture of the sixth sub-via 460b is smaller than that of the second via 451. Thereafter, a connecting rod 490 is formed in the sixth sub-via 460b. One end of the connecting rod 490 is connected to and insulated from the first electrode 430.

[0095] It should be understood that since the first connecting rod 490 passes through the third sacrificial layer 460, the second electrode layer 450 and the second sacrificial layer 440. Therefore, in some embodiments, the respective portions of the connecting rod 490 can also be formed in the process of forming the second sacrificial layer 440, the second electrode layer 450 and the third sacrificial layer 460 respectively. The present application does not make too many limitations in this regard, as long as the connecting rod 490 is formed before the formation of the third electrode, particularly the lower portion of the third electrode.

[0096] The material of the connecting rod 490 is a single material of silicon nitride or a multi-layer composite material randomly stacked by silicon nitride and polycrystalline silicon or / and amorphous silicon. The contact surface of the connecting rod 490 and the first electrode 430 is an insulating material.

[0097] After the formation of the connecting rod 490, as shown, Figure 7C a lower material 471 of the third electrode is deposited. The lower material 471 that is retained after the preparation is completed is Figure 4 ​​The lower portion 471 of the MEMS capacitive sensor 400 shown. The lower material fills the fifth sub-via 460a and covers the top of the third sacrificial layer 460 and the connecting rod 490. The contact surface between the connecting rod 490 and the lower material 471 is an insulating material. Similarly, when the projection of the fifth sub-via 460a is adjacent to and surrounds the projection of the first sub-via 480a, as... Figure 7C As shown in Figure (a), the deposited lower layer material 471 has a relatively flat surface. When the projection of the fifth sub-via 460a is concentric with the projection of the first sub-via 480a, as... Figure 7C As shown in Figure (b), the deposited lower layer material 471 has a second groove 460c above the fifth sub-through hole 460a.

[0098] After depositing the lower layer material 471, the lower layer material 471 is patterned to form a release hole 471a. Subsequently, a portion of the second sacrificial layer 440 and a portion of the third sacrificial layer 460 are removed through this release hole to form a second gap 441 between the second electrode 450 and the first electrode 430, and a third gap 461 between the third electrode 470 and the second electrode 450. The second gap 441 and the third gap 461 are connected via a second through-hole. Specifically, in the thickness direction Z, the projection of the vibration-sensitive region of the first electrode 430 overlaps with the projection range of the second gap 441, or the projection of the vibration-sensitive region falls within the projection range of the second gap 441; the projections of the third gap 461 and the second gap 441 at least partially overlap.

[0099] After the second gap 441 and the third gap 461 are formed, a sealing structure 471b is formed to fill the release hole 471a, thereby sealing the second gap 441 and the third gap 461 and preventing oil droplets from contaminating the second gap 441 and the third gap 461. In other words, the release hole 471a and the sealing structure 471b can be different forms of the same location at different preparation stages.

[0100] In some embodiments, for Figure 7C In the example of concentric projection shown in Figure (b), while forming the sealing structure 471b that fills the release hole 471a, the film material of the sealing structure 471b is also deposited in the second groove 460c. Specifically, the film material of the sealing structure 471b can fill the release hole 471a and the second groove 460c and cover the underlying material 471. Subsequently, the film material on the surface of the underlying material 471 is removed by a process such as chemical mechanical polishing (CMP), and the upper surface of the remaining film material of the sealing structure 471b is flush with or at the same height as the upper surface of the underlying material 471 in the thickness direction Z. Completing the filling of the second groove 460c simultaneously with the formation of the sealing structure 471b simplifies the preparation process and saves production costs.

[0101] like Figure 7D As shown, after sealing the second and third gaps, an upper layer material 472 of the third electrode is deposited, covering the lower layer material 471 and the film material of the sealing structure 471b. After fabrication, the retained upper layer material 472 constitutes the upper portion 472 of the third electrode 470. The upper portion 472 and the lower portion 471 together form the complete third electrode 470. Figure 7D Figure (a) shows the structure after depositing the upper material 472 when the projection of the fifth sub-via 460a is adjacent to and surrounds the projection of the first sub-via 480a. Figure 7D Figure (b) shows the structure after depositing the upper layer material 472 when the projection of the fifth sub-through hole 460a and the projection of the first sub-through hole 480a are concentric.

[0102] After the third electrode 470 is formed, it is patterned to form the third sub-via 480c. Figure 7E Figure (a) shows the structure after the third sub-via 480c is formed when the projection of the fifth sub-via 460a is adjacent to and surrounds the projection of the first sub-via 480a. In this figure, the third sacrificial layer 460 exposed by the third sub-via 480c fills and extends beyond the second sub-via 480b. Figure 7E Figure (b) shows the structure after the formation of the third sub-via 480c when the projections of the fifth sub-via 460a and the first sub-via 480a are concentric. The third sacrificial layer 460 exposed by the third sub-via 480c is located within the second sub-via 480b. Furthermore, as... Figure 7E As shown in Figure (b), the third sub-through hole 480c also passes through and exposes the membrane material of the filling sealing structure 471b in the second groove 460c.

[0103] After forming the third sub-via 480c, a back cavity 411 penetrating the substrate 410 is formed. Subsequently, a portion of the first sacrificial layer 420, as well as the second sacrificial layer 440 and the third sacrificial layer 460 in the first via 480, are released, forming a through-structure of the first gap 421 and the first via 480. The retained first sacrificial layer 420 forms the first anchor region, the retained second sacrificial layer 440 forms the second anchor region, and the retained third sacrificial layer 460 forms the third anchor region.

[0104] It should be understood that, for the case that the projection of the fourth sub-via 240a and / or the fifth sub-via 460a in the thickness direction Z is adjacent to and surrounds the periphery of the projection of the first sub-via, it is more beneficial to make the corresponding sacrificial layer have a planarized surface, thereby reducing the process difficulty and complexity of subsequent steps. For the above-mentioned related case of concentric projection, since the third sub-via 480c also passes through and exposes the film layer material in the second recess 460c. Therefore, when the sacrificial layer is released, if the film layer material is not released, a structure as shown in FIG. 8A will be formed, and if the film layer material is also released, a structure as shown in FIG. 8B will be formed. The corresponding film layer material can be selected according to the actual working condition to obtain the two structures. Figure 7F Figure 7F

[0105] In a preferred embodiment, as shown in FIG. 7, the projection of the first via 270 and the first via 480 in the thickness direction Z falls within the projection range of the corresponding back cavity, ensuring that the back cavity is in smooth communication with the external airflow through the first via 270 or 480 during device operation, effectively reducing the interference of environmental air pressure changes on device performance. At the same time, the oil droplets carried in the airflow can also directly pass through the first via into the back cavity, reducing the risk of oil droplet accumulation. Figures 6A-7E

[0106] The embodiments of the present application described above are not exhaustive in describing all details, nor limit the present application to only the specific embodiments described above. It is obvious that, according to the above description, many modifications and changes can be made. The present description selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present application, so that those skilled in the art can well utilize the present application and make modifications and uses on the basis of the present application. The scope of protection of the present application should be subject to the scope defined by the claims of the present application.​​​

Claims

1. A MEMS capacitive sensor, wherein, 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, wherein, 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, wherein, 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, wherein, 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, wherein, 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.

6. The MEMS capacitive sensor according to claim 5, wherein, 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.

7. A method for fabricating a MEMS capacitive sensor, wherein, include: Provide substrate; A first sacrificial layer is formed on the substrate; A first electrode is formed on the first sacrificial layer, and the first electrode has a first sub-through hole; A second sacrificial layer is formed on the first electrode; A second electrode is formed on the second sacrificial layer, and the second electrode has a second sub-through hole; A back cavity is formed that extends through the substrate in the thickness direction; as well as The sacrificial layer is released to form a first gap between the first electrode and the substrate, and a second gap between the second electrode and the first electrode. The first sacrificial layer connected to the circumferential edge of the first electrode is retained to form a first anchor layer, and the second sacrificial layer connected to the circumferential edge of the second electrode is retained to form a second anchor layer. Wherein, after the sacrificial layer is released, the first sub-through hole and the second sub-through hole are connected to form a first through hole, the first through hole is connected to the back cavity through the first gap, and in the thickness direction, the projection of the first through hole and the projection of the second gap are independent of each other.

8. The preparation method according to claim 7, wherein, In the thickness direction, the projection of the first through hole falls within the projection range of the back cavity.

9. The preparation method according to claim 7, wherein, The formed second sacrificial layer has a fourth sub-via, the projection of which, in the thickness direction, is adjacent to and surrounds the outer periphery of the first sub-via. The steps for forming the second electrode include: A material layer for the second electrode is deposited, which fills the fourth sub-via and covers the second sacrificial layer. The material layer is patterned to form the second sub-via, which exposes the second sacrificial layer. In the thickness direction, the projection of the second sub-via overlaps with the projection of the first sub-via, and the exposed second sacrificial layer fills and extends beyond the first sub-via.

10. The preparation method according to claim 7, wherein, The formed second sacrificial layer has a fourth sub-via, and in the thickness direction, the projection of the first sub-via falls within the projection range of the fourth sub-via. The steps for forming the second electrode include: A material layer for the second electrode is deposited, which fills the fourth sub-via and covers the second sacrificial layer. The material layer is patterned to form the second sub-via, which exposes the second sacrificial layer. In the thickness direction, the projection of the second sub-via overlaps with the projection of the first sub-via, and the exposed second sacrificial layer is located in the first sub-via.

11. The preparation method according to claim 7, wherein, 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 preparation method further includes: A second through hole is formed on the fixed electrode, and the second gap and the second through hole are connected.

12. The preparation method according to claim 11, wherein, 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. After forming the second electrode, the preparation method further includes: A third sacrificial layer is formed on the second electrode; A third electrode is formed on the third sacrificial layer, and the third electrode has a third sub-via. Wherein, after the sacrificial layer is released, a third gap is formed between the second electrode and the third electrode, and in the thickness direction, the projection of the third gap at least partially overlaps with the projection of the second gap. The third sacrificial layer connected to the circumferential edge of the third electrode is retained to form a third anchor layer, and the first through hole also includes the third sub-through hole.

13. The preparation method according to claim 12, wherein, The formed third sacrificial layer has a fifth sub-via, the projection of which, in the thickness direction, is adjacent to and surrounds the outer periphery of the first sub-via. The steps for forming the third electrode include: A lower layer material is deposited for the third electrode, the lower layer material filling the fifth sub-via and covering the third sacrificial layer; Depositing an upper layer material of the third electrode, the upper layer material covering the lower layer material; and The upper and lower materials are patterned to form the third sub-via, wherein the projection of the third sub-via overlaps with the projection of the first sub-via in the thickness direction, and the third sacrificial layer exposed by the third sub-via fills and extends beyond the second sub-via.

14. The preparation method according to claim 12, wherein, The formed third sacrificial layer has a fifth sub-via, and in the thickness direction, the projection of the first sub-via falls within the projection range of the fifth sub-via. The steps for forming the third electrode include: A lower layer material is deposited for the third electrode, the lower layer material filling the fifth sub-via and covering the third sacrificial layer; Depositing an upper layer material of the third electrode, the upper layer material covering the lower layer material; and The upper and lower materials are patterned to form the third sub-via, wherein the projection of the third sub-via overlaps with the projection of the first sub-via in the thickness direction, and the third sacrificial layer exposed by the third sub-via is located in the second sub-via.

15. The preparation method according to claim 13 or 14, wherein, Before depositing the underlying material, the preparation method further includes: A connecting rod is formed, which passes through the second through hole and connects to the first electrode. The diameter of the connecting rod is smaller than the diameter of the second through hole. After the underlying material is deposited, the connecting rod is also connected to the underlying material.

16. The preparation method according to claim 15, wherein, Between depositing the lower layer material and depositing the upper layer material, the preparation method further includes: The underlying material is patterned to form 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 A sealing structure is formed to fill the release hole.

17. The preparation method according to claim 16, wherein, The step of forming a sealing structure that fills the release hole includes: A deposited film material is formed, which fills the release pores and covers the underlying material; and The film material on the surface of the lower material is removed, and the film material remaining in the release hole forms the sealing structure. Wherein, when the projection of the first sub-through hole falls within the projection range of the fifth sub-through hole, the surface of the deposited lower layer material has a groove, and the deposited film material also fills the groove.

18. The preparation method according to claim 16, wherein, The release sacrificial layer includes: Between forming the release hole and forming the sealing structure, a portion of the third sacrificial layer and the second sacrificial layer are removed through the release hole to form the second gap and the third gap; and After forming the back cavity, a portion of the first sacrificial layer is removed to form the first gap, and the second and third sacrificial layers within the first through hole are removed.

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