Membrane-based capacitive sensor

Abstract

The application discloses a MEMS capacitive sensor. The MEMS capacitive sensor comprises a substrate with a back cavity of a first shape, and a structure layer with a movable capacitive structure of a second shape and a first through hole, wherein, in the projection in the thickness direction, the movable capacitive structure covers part of the back cavity, and the uncovered back cavity is located between the first through hole and the movable capacitive structure. By optimizing the shape matching relationship between the back cavity and the movable capacitive structure, the first through hole is closer to the back cavity and farther from the movable capacitive structure, so that a larger safety margin can be left while ensuring the smoothness of the airflow channel, and the accumulated oil droplets can be prevented from causing the movable capacitive structure to fail.

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] Capacitive sensors fabricated using micromachining methods in the Z-direction are often used in exposed air and may be contaminated by oil droplets. Due to the oleophilic and hydrophobic properties of the materials used in capacitive sensors, especially silicon nitride and polycrystalline silicon, oil droplets can easily adhere to and penetrate into the gaps in the microstructure. This is especially true in areas with submicron-level pores, where oil droplets can easily intrude and accumulate between the movable capacitor plates, leading to adhesion or short circuits, and ultimately causing device failure.

[0004] To address this issue, existing technologies employ airtight capacitor electrodes. While this effectively blocks oil droplet penetration, the solution requires special processes to match the airtight electrode structure during wafer-level CP testing and packaging. This results in the inability to reuse existing mass production testing and packaging processes, significantly increasing manufacturing costs and process complexity. Utility Model Content

[0005] In view of the above problems, the purpose of this application is to provide a MEMS capacitive sensor.

[0006] According to one aspect of this application, a MEMS capacitive sensor is disclosed, characterized in that it comprises: a substrate having a back cavity with a first shape; and a structural layer having a movable capacitor structure with a second shape and a first through hole, wherein, in a projection along the thickness direction, the movable capacitor structure covers a portion of the back cavity, and the uncovered portion of the back cavity is located between the first through hole and the movable capacitor structure.

[0007] Optionally, the first shape is a polygon and the second shape is a circle.

[0008] Optionally, the polygon is a square.

[0009] Optionally, the first through hole is located at the outer periphery of the apex corner of the square, and the uncovered back cavity is triangular in shape.

[0010] Optionally, on the projection in the thickness direction, the first through hole has a first distance between itself and the corresponding apex corner, and at least a second distance between itself and the movable capacitor structure, wherein the first distance is less than the second distance.

[0011] Optionally, the movable capacitor structure also has an area not covering the back cavity in the projection along the thickness direction.

[0012] Optionally, the structural layer comprises: a first electrode connected to the substrate via a first anchor layer, wherein a first gap exists between the first electrode and the substrate; and a second electrode connected to the first electrode via a second anchor layer, wherein a second gap exists between the second electrode and the first electrode, wherein, in the projection along the thickness direction, the movable capacitor structure is surrounded by the second anchor layer and / or the first anchor layer.

[0013] Optionally, one of the first electrode and the second electrode is a fixed electrode, and the other is a vibrating electrode.

[0014] Optionally, the fixed electrode further has a second through hole that exposes the vibrating electrode.

[0015] Optionally, the first through hole connects to the back cavity via the first gap.

[0016] According to the MEMS capacitive sensor provided in this application, by optimizing the shape matching relationship between the back cavity and the movable capacitor structure, the first through hole is closer to the back cavity and farther from the movable capacitor structure. Therefore, while ensuring the smooth flow of air, a larger safety margin can be provided to avoid the failure of the movable capacitor structure due to the accumulation of oil droplets, which is conducive to improving the reliability and service life of the device. 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 top view of a MEMS capacitive sensor is shown.

[0019] Figure 2 Show Figure 1 The cross-sectional view of the MEMS capacitive sensor shown is shown.

[0020] Figure 3 A top view of a MEMS capacitive sensor according to an embodiment of this application is shown;

[0021] Figure 4 Show Figure 3 The image shows a cross-sectional view of a MEMS capacitive sensor. 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] Figure 1 A top view of a MEMS capacitive sensor is shown. Figure 2 Show Figure 1 The diagram shows a cross-sectional view of a MEMS capacitive sensor. Wherein, Figure 2 Figure (a) is along Figure 1 A cross-sectional view taken from line A-A'. Figure 2 Figure (b) is along Figure 1 A cross-sectional view taken from line B-B'.

[0027] Combination Figure 1 and Figure 2The MEMS capacitive sensor 100 includes a substrate 110 and a structural layer. The structural layer includes a first anchor layer 120, a first electrode 130, a second anchor layer 140, and a second electrode 150. The functional area of ​​the MEMS capacitive sensor is formed in the structural layer. The functional area mainly includes the movable capacitor structure of the MEMS capacitive sensor.

[0028] The substrate 110 has a back cavity 111, which extends through the substrate 110 in the thickness direction. Figure 1 In the accompanying figures, the first direction is the X direction, the second direction is the Y direction, and the top view of the MEMS capacitive sensor is also its projection onto the XY plane. The third direction is the Z direction, which is the thickness direction of the substrate.

[0029] The first anchor layer 120 is located between the circumferential edge of the first electrode 130 and the substrate 110, for fixing the first electrode 130 and forming a first gap between the first electrode 130 and the substrate 110. The second anchor layer 140 is located between the circumferential edge of the second electrode 150 and the circumferential edge of the first electrode 130, for fixing the second electrode 150 and forming a second gap between the second electrode 150 and the first electrode 130.

[0030] exist Figure 1 and Figure 2 In the example, the first electrode 130 is a vibrating electrode, and the second electrode 150 is a fixed electrode. The connection position between the first anchor layer 120 or the second anchor layer 140 and the first electrode 130 defines the vibration-sensitive area on the first electrode 130, that is, defines the position of the movable capacitor structure. For example, Figure 1 As shown, in the thickness direction Z of the substrate 110, the projections of both the back cavity 111 and the movable capacitor structure are circular, and the projection of the back cavity 111 is covered by the projection of the movable capacitor structure. Specifically, in some embodiments, such as Figure 2 As shown in Figure (a), since the width of the portion of the first electrode 130 surrounded by the second anchor layer 140 is smaller than the width of the portion surrounded by the first anchor layer 120, the position range of the movable capacitor structure is constrained by the second anchor layer 140.

[0031] When the first electrode 130 deforms under external pressure, the distance of the second gap in the thickness direction Z of the substrate 110 changes, thereby causing a change in the capacitance value. To achieve pressure balance on both sides of the first electrode 130 in the non-operating state, multiple first through-holes 131 are formed on the first electrode 130. To form an airflow channel between the second gap and the outside, multiple second through-holes 151 are formed on the second electrode 150. It should be understood that the second anchor layer 140 can also be an irregular structure, for example, in... Figure 2(b) In the figure, the second anchor layer 140 at the corresponding position is removed to avoid the first through hole 131 being blocked, thus ensuring airflow. Furthermore, in this embodiment, the first through hole 131 can be formed at any relevant position in the prior art, and this application does not impose excessive restrictions.

[0032] 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 in the opposite direction. Since the number of first through-holes 131 is far less 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. Therefore, in Figure 1 and Figure 2 In one example, a groove 112 is also provided on the substrate 110 for collecting oil droplets carried in the airflow. In other embodiments, the groove 112 may extend through the substrate 110 in the thickness direction, that is, expand the range of the back cavity 111 so that the projection of the first through hole 131 in the thickness direction Z falls within the projection range of the back cavity 111.

[0033] However, due to the limited area of ​​the MEMS capacitive sensor 100, a larger vibration-sensitive area is needed to improve the device's sensitivity. This means that the distance between the groove 112 and the movable capacitor structure in the X direction is limited, and the safety margin between the first through-hole 131 and the vibration-sensitive area, i.e. Figure 1 The area S shown is relatively small, and accumulated oil droplets may still intrude into the vibration-sensitive area. Furthermore, forming this groove 112 separately would make the fabrication process of the MEMS capacitive sensor 100 more complex and costly.

[0034] Figure 3 This is a top view of a MEMS capacitive sensor according to an embodiment of this application. Figure 4 Show Figure 3 The diagram shows a cross-sectional view of a MEMS capacitive sensor. Wherein, Figure 4 Figure (a) is along Figure 3 A cross-sectional view taken from line A-A'. Figure 4 Figure (b) is along Figure 3 A cross-sectional view taken from line B-B'.

[0035] Combination Figure 3 and Figure 4 The MEMS capacitive sensor 200 includes a substrate 210 and a structural layer. The structural layer includes a first anchor layer 220, a first electrode 230, a second anchor layer 240, and a second electrode 250. The movable capacitor structure of the MEMS capacitive sensor is formed in the structural layer.

[0036] The substrate 210 has a back cavity 211 that extends through the substrate 210 in the thickness direction Z. The back cavity 211 has, for example, a first shape, which can be embodied as the back cavity 211 having a first shape on its projection in the thickness direction Z. The first shape can be polygonal. Figure 3 and Figure 4 For example, a square.

[0037] The first anchor layer 220 is located between the circumferential edge of the first electrode 230 and the substrate 210, for fixing the first electrode 230 and forming a first gap between the first electrode 230 and the substrate 210. The second anchor layer 240 is located between the circumferential edge of the second electrode 250 and the circumferential edge of the first electrode 230, for fixing the second electrode 250 and forming a second gap between the second electrode 250 and the first electrode 230.

[0038] For example, the first electrode 230 is a vibrating electrode, and the second electrode 250 is a fixed electrode. The connection position between the first anchor layer 220 or the second anchor layer 240 and the first electrode 230 defines the vibration-sensitive area on the first electrode 230, that is, defines the position of the movable capacitor structure.

[0039] exist Figure 4 In the example, the second anchor layer 240 is closer to the center of the MEMS capacitive sensor 200 than the first anchor layer 220. This is exemplified, for instance, by... Figure 4 In Figure (a), the boundary FA is closer to the center of the MEMS capacitive sensor than the first anchor layer 220, and in Figure (b), the boundary FC is closer to the center of the MEMS capacitive sensor than the first anchor layer 220. The second anchor layer 240 has a stronger constraint capability, and therefore the position of the movable capacitor structure is constrained by the second anchor layer 240. That is, in the thickness direction Z, the projection of the second anchor layer 240 is adjacent to and surrounds the position of the movable capacitor structure, while the projection of the first anchor layer 220 is located on the periphery of the movable capacitor structure.

[0040] The movable capacitor structure may have a second shape, for example, as manifested in its projection along the thickness direction Z. This second shape may be circular and intersect with the projection of the back cavity 211. Specifically, the projection along the thickness direction Z includes a first type of region, a second type of region, and a third type of region. The first type of region is the area where the movable capacitor structure and the back cavity 211 overlap; the second type of region is a single back cavity region not covered by the movable capacitor structure; and the third type of region is a single movable capacitor structure region not covered by the back cavity. Figure 3 In this context, a single back cavity region is, for example, a triangular shape between boundaries FC and FD, while a single movable capacitor structure region is, for example, an arc shape between boundaries FA and FB. Furthermore, as... Figure 4As shown in Figure (a), boundary FA is closer to the boundary of MEMS capacitive sensor 200 than boundary FB, and in Figure (b), boundary FC is closer to the center of MEMS capacitive sensor 200 than boundary FD.

[0041] When the first electrode 230 deforms under external pressure, the distance of the second gap in the thickness direction Z of the substrate 210 changes, thereby causing a change in the capacitance value. To achieve pressure balance on both sides of the first electrode 230 in the non-operating state, multiple first through holes 231 are formed on the first electrode 230. To form an airflow channel between the second gap and the outside, multiple second through holes 251 are formed on the second electrode 250, exposing the first electrode 230.

[0042] The first through hole 231 communicates with the back cavity 211 via the first gap. For example, the second electrode 250 may extend along the sidewall of the first through hole 231 to the first electrode 230 to prevent the first through hole 231 from being blocked. Accordingly, as... Figure 4 As shown in Figure (b), the second anchor layer 240 is also penetrated by the first through hole 231.

[0043] exist Figure 3 and Figure 4 In the example, the first through-hole 231 is located at the outer periphery of the apex corner of the square back cavity 211. On the same plane, for example, in the projection along the thickness direction Z, the first through-hole 231 is at least a second distance h2 from the corresponding apex corner and at least a second distance h1 from the movable capacitor structure, where h1 < h2. Because the first through-hole 231 is closer to the back cavity 211, it facilitates gas flow. Simultaneously, the first through-hole 231 is farther from the movable capacitor structure, thus allowing for a larger safety margin (e.g., ...). Figure 3 (In the S region), to avoid the accumulation of oil droplets that could cause the movable capacitor structure to fail.

[0044] Furthermore, in the portion without the first through-hole 231, the projection along the thickness direction Z can be a single movable capacitor structure area, meaning the movable capacitor structure extends beyond the back cavity 211. This facilitates increasing the area of ​​the movable capacitor structure, thereby improving the sensitivity of the MEMS capacitive sensor.

[0045] It should be noted that, Figure 4In the example shown in Figure (a), the movable capacitor structure extends beyond the back cavity 211 specifically because the boundary FA is farther from the central axis of the MEMS capacitive sensor 200 and closer to the boundary of the MEMS capacitive sensor 200 compared to the boundary FB. That is, in the thickness direction Z, the projection range of the back cavity 211 is surrounded by the projection range of the second anchor layer 240, but is not adjacent to the projection of the second anchor layer 240. However, in this example, the range of the movable capacitor structure is still limited by the boundary FA of the second anchor layer 240, which is closer to the central axis of the MEMS capacitive sensor than the boundary FE. That is, in the thickness direction Z, the projection range of the first anchor layer 220 falls within the projection range of the second anchor layer 240.

[0046] In some other embodiments, the distance between the boundaries FA and FE and the central axis of the MEMS capacitive sensor in the X direction can be made equal by adjusting the etching process duration. That is, in the thickness direction Z, the projection range of the first anchor layer 220 and the projection range of the second anchor layer 240 completely overlap.

[0047] In some other embodiments, the boundary FA can be positioned further away from the central axis of the MEMS capacitive sensor than the boundary FE, i.e., in the thickness direction Z, the projection range of the second anchor layer 240 falls within the projection range of the first anchor layer 220. It should be understood that, at least in the cross-section along line A-A', the range of the movable capacitor structure is limited by the first anchor layer 220.

[0048] In other words, this application does not impose specific restrictions on the area of ​​the single capacitor structure region. Therefore, the area of ​​the movable capacitor region can be expanded in the direction where the first through hole 231 is not provided, according to the actual working conditions, thereby improving the sensitivity of the MEMS capacitive sensor.

[0049] It is understood that in some embodiments, the first electrode may be a fixed electrode and the second electrode may be a vibrating electrode. Accordingly, the first electrode may also have a second through hole, and the second electrode may also have a vibration-sensitive area.

[0050] According to the MEMS capacitive sensor provided in this application, by optimizing the shape matching relationship between the back cavity and the movable capacitor structure, the first through hole is closer to the back cavity and farther from the movable capacitor structure. Therefore, while ensuring the smooth flow of air, a larger safety margin can be provided to avoid the failure of the movable capacitor structure due to the accumulation of oil droplets, which is conducive to improving the reliability and service life of the device.

[0051] 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: Substrate having a back cavity of a first shape; as well as The structural layer has a movable capacitor structure of a second shape and a first through-hole. In the thickness direction projection, the movable capacitor structure covers part of the back cavity, and the uncovered back cavity is located between the first through hole and the movable capacitor structure.

2. The MEMS capacitive sensor according to claim 1, characterized in that, The first shape is a polygon, and the second shape is a circle.

3. The MEMS capacitive sensor according to claim 2, characterized in that, The polygon is a square.

4. The MEMS capacitive sensor according to claim 3, characterized in that, The first through hole is located at the outer perimeter of the top corner of the square, and the uncovered back cavity is triangular in shape.

5. The MEMS capacitive sensor according to claim 4, characterized in that, On the projection along the thickness direction, the first through hole has a first distance between itself and the corresponding apex corner, and at least a second distance between itself and the movable capacitor structure, wherein the first distance is less than the second distance.

6. The MEMS capacitive sensor according to claim 3, characterized in that, On the projection along the thickness direction, the movable capacitor structure also has an area that does not cover the back cavity.

7. The MEMS capacitive sensor according to any one of claims 1-6, characterized in that, The structural layer includes: A first electrode is connected to the substrate via a first anchor layer, and a first gap exists between the first electrode and the substrate; and The second electrode is connected to the first electrode via a second anchor layer, and a second gap exists between the second electrode and the first electrode. In the projection along the thickness direction, the movable capacitor structure is surrounded by the second anchor layer and / or the first anchor layer.

8. The MEMS capacitive sensor according to claim 7, characterized in that, One of the first electrode and the second electrode is a fixed electrode, and the other is a vibrating electrode.

9. The MEMS capacitive sensor according to claim 8, characterized in that, The fixed electrode also has a second through hole, which exposes the vibrating electrode.

10. The MEMS capacitive sensor according to claim 7, characterized in that, The first through hole connects to the back cavity via the first gap.

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