MEMS capacitive pressure sensor and preparation method thereof

Abstract

The invention relates to an MEMS capacitive pressure sensor and a preparation method thereof, and relates to the technical field of microelectronics. The pressure sensor includes a conductive substrate; the pressure sensor comprises a cavity area and an edge area surrounding the cavity area in the direction of the plane where the conductive substrate is located; the first electrode layer is formed on the surface of the conductive substrate and located in the cavity area; the first electrode layer comprises a plurality of annular first electrodes which are arranged in an insulating manner; the pressure strain diaphragm is positioned on one side, far away from the conductive substrate, of the first electrode layer; the second electrode layer is formed on the side, facing the first electrode layer, of the pressure strain diaphragm and located in the cavity area; the second electrode layer comprises a plurality of annular second electrodes which are arranged in an insulating manner; the insulating layer is formed between the conductive substrate and the pressure strain diaphragm and is positioned in the edge region; the first electrodes and the second electrodes are alternately arranged at intervals in the direction from the center point in the plane where the conductive substrate is located to the edge area. The problem that the first electrode and the second electrode are contacted by mistake when the pressure sensor is used is avoided.

Description

Technical Field

[0001] The present application relates to the field of microelectronics technology, and in particular to a MEMS capacitive pressure sensor and a method for preparing the same. Background Art

[0002] Social production has a huge demand for pressure monitoring, especially in the fields of industry and automobiles. Micro-Electro-Mechanical System (MEMS) pressure sensors have been widely used in consumer electronics, industrial measurement and control, aerospace, medical equipment, and automobile manufacturing due to their small size, high performance, high reliability, low cost, easy mass production, and strong portability. They are the most successful case of MEMS sensor marketization.

[0003] At present, the mainstream technologies of MEMS pressure sensors can be divided into piezoresistive and capacitive. Piezoresistive uses the piezoresistive effect. When the piezoresistive material is subjected to external pressure, its resistance will change, thereby realizing pressure detection; capacitive pressure sensors are composed of strained thin films to form capacitors. Pressure changes the capacitance of the capacitor to realize pressure detection. Piezoresistive pressure sensors have the advantage of high linearity compared to capacitive pressure sensors, but their biggest disadvantage is the temperature drift phenomenon. This is because the piezoresistors of piezoresistive pressure sensors are made of silicon doping, and their resistance value is easily affected by temperature. Capacitive pressure sensors have the advantages of low power consumption, high sensitivity, and excellent temperature characteristics. They have great advantages when working in a wide temperature range. Since the pressure strain film as the capacitor plate is not parallel to the other capacitor plate when it is deformed under pressure, the linearity of capacitive pressure sensors is worse than that of piezoresistive pressure sensors.

[0004] Therefore, there is an urgent need to provide a capacitive pressure sensor with good linearity. Summary of the invention

[0005] Based on this, it is necessary to provide a MEMS capacitive pressure sensor and a preparation method thereof that can improve the linearity of the capacitive pressure sensor in order to solve the problem of poor linearity of the capacitive pressure sensor.

[0006] In a first aspect, the present application provides a MEMS capacitive pressure sensor, comprising:

[0007] A conductive substrate; along the direction of the plane where the conductive substrate is located, the pressure sensor includes a cavity area and an edge area surrounding the cavity area;

[0008] A first electrode layer is formed on one side surface of the conductive substrate and is located in the cavity area; the first electrode layer includes a plurality of insulated annular first electrodes;

[0009] A pressure strain diaphragm, located on a side of the first electrode layer away from the conductive substrate;

[0010] A second electrode layer is formed on a side of the pressure strain diaphragm facing the first electrode layer and is located in the cavity area; the second electrode layer includes a plurality of insulated annular second electrodes;

[0011] an insulating layer formed between the conductive substrate and the pressure-strained diaphragm and located in the edge region;

[0012] In a direction from a center point in a plane where the conductive substrate is located to the edge region, the first electrodes and the second electrodes are arranged alternately and at intervals.

[0013] In one embodiment, the cavity region includes a first cavity region and a second cavity region surrounding the first cavity region;

[0014] The first electrode and the second electrode are both located in the second cavity region.

[0015] In one of the embodiments, it further includes a first metal pad and a second metal pad located in the edge region;

[0016] The first metal pad is formed on a side of the pressure strain diaphragm away from the conductive substrate, the second metal pad is formed on a side of the insulating layer away from the conductive substrate, and the second metal pad is electrically connected to the conductive substrate through the insulating layer.

[0017] In one of the embodiments, along a direction from the cavity area to the edge area, the first metal pad and the second metal pad are disposed on two sides of the cavity area.

[0018] In one embodiment, in a direction from the conductive substrate to the pressure-strained diaphragm, a sum of a size of the first electrode layer and a size of the second electrode layer is less than or equal to a size between the conductive substrate and the pressure-strained diaphragm.

[0019] In one embodiment, along a direction from the conductive substrate to the pressure-strained diaphragm, sizes of the first electrodes are all the same, and sizes of the second electrodes are all the same.

[0020] In one of the embodiments, at least one of the conductive substrate and the pressure-strained diaphragm is made of a material including low-resistance silicon.

[0021] In one embodiment, the material used to make at least one of the first electrode and the second electrode includes at least one of gold and aluminum.

[0022] In a second aspect, the present application provides a method for preparing a MEMS capacitive pressure sensor, comprising:

[0023] Providing a conductive substrate; along the direction of the plane where the conductive substrate is located, the pressure sensor includes a cavity area and an edge area surrounding the cavity area;

[0024] Depositing an insulating layer on one surface of the conductive substrate;

[0025] Etching a portion of the insulating layer in the cavity area to form a plurality of insulatingly arranged annular first grooves;

[0026] In the first groove, a first electrode is prepared to form a first electrode layer;

[0027] etching another portion of the insulating layer in the cavity region;

[0028] Depositing an insulating layer on a surface of the conductive substrate facing the first electrode layer;

[0029] Etching a portion of the insulating layer in the cavity area to form a plurality of insulatingly arranged annular second grooves; the first grooves and the second grooves are arranged alternately and at intervals in a direction from a center point in a plane where the conductive substrate is located to the edge area;

[0030] In the second groove, a second electrode is prepared to form a second electrode layer;

[0031] A pressure strain diaphragm is prepared on a surface of the second electrode layer away from the first electrode layer;

[0032] Etching a portion of the pressure-strained diaphragm in the cavity region in a direction from the pressure-strained diaphragm toward the conductive substrate to form an etching hole penetrating the pressure-strained diaphragm;

[0033] The insulating layer in the cavity area is etched based on the etched hole, and the etched hole is filled.

[0034] In one embodiment, it also includes:

[0035] Etching a portion of the pressure-strained diaphragm and the insulating layer in the edge region in a direction from the pressure-strained diaphragm toward the conductive substrate to form a through hole penetrating the pressure-strained diaphragm and the insulating layer;

[0036] A first metal pad is prepared on a surface of the pressure strain diaphragm away from the conductive substrate, and a second metal pad is prepared on a surface of the insulating layer where the through hole is located away from the conductive substrate; the second metal pad is electrically connected to the conductive substrate via the through hole where the insulating layer is located.

[0037] In the above-mentioned MEMS capacitive pressure sensor and its preparation method provided by the present application, the MEMS capacitive pressure sensor includes a conductive substrate; along the direction of the plane where the conductive substrate is located, the pressure sensor includes a cavity area and an edge area surrounding the cavity area; a first electrode layer is formed on one side surface of the conductive substrate and is located in the cavity area; the first electrode layer includes a plurality of insulating annular first electrodes; a pressure strain diaphragm is located on the side of the first electrode layer away from the conductive substrate; a second electrode layer is formed on the side of the pressure strain diaphragm facing the first electrode layer and is located in the cavity area; the second electrode layer includes a plurality of insulating annular second electrodes; an insulating layer is formed between the conductive substrate and the pressure strain diaphragm and is located in the edge area; along the center of the plane where the conductive substrate is located In the direction of the point pointing to the edge area, the first electrode and the second electrode are alternately and spaced apart; it can be seen that the present application sets a plurality of annular first electrodes and a plurality of annular second electrodes, and alternately sets them in the direction along the plane where the conductive substrate is located, which is beneficial to increase the effective area between the capacitor plates composed of the conductive substrate and the first electrodes, and the capacitor plates composed of the pressure strain diaphragm and the second electrodes, and is beneficial to increase the overall sensitivity of the pressure sensor; and the first electrode and the second electrode are spaced apart in the direction of the plane where the conductive substrate is located, which is beneficial to avoid the situation where the first electrode and the second electrode accidentally contact each other when pressure is applied to the surface of the pressure strain diaphragm, thereby helping to improve the linearity of the capacitive pressure sensor and improve the pressure detection accuracy of the capacitive sensor. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 A top view of a MEMS capacitive pressure sensor provided in an embodiment of the present application;

[0039] Figure 2 Provided for the embodiments of this application Figure 1 A cross-sectional view of AA';

[0040] Figure 3 A partial stereoscopic diagram of a MEMS capacitive pressure sensor provided in an embodiment of the present application;

[0041] Figure 4 Provided for the embodiments of this application Figure 1 A preparation flow chart of the first electrode layer;

[0042] Figure 5 Provided for the embodiments of this application Figure 1 A preparation flow chart of the second electrode layer and the pressure strain diaphragm;

[0043] Figure 6 Provided for the embodiments of this application Figure 1 A preparation flow chart of a sealed cavity;

[0044] Figure 7 Provided for the embodiments of this application Figure 1 A preparation flow chart of the first metal pad and the second metal pad. DETAILED DESCRIPTION

[0045] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are described in detail below in conjunction with the accompanying drawings. In the following description, many specific details are set forth to facilitate a full understanding of the present application. However, the present application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present application, so the present application is not limited by the specific embodiments disclosed below.

[0046] In the description of the present application, it should be understood that if the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. appear, the orientation or position relationship indicated by these terms is based on the orientation or position relationship shown in the accompanying drawings, which is only for the convenience of describing the present application and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present application.

[0047] In addition, if the terms "first" or "second" appear, these terms are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include at least one of the features. In the description of this application, if the term "plurality" appears, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0048] In this application, unless otherwise clearly specified and limited, if the terms "installed", "connected", "connected", "fixed" and the like appear, these terms should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integrated connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to the specific circumstances.

[0049] In the present application, unless otherwise clearly specified and limited, if there is a description that a first feature is "above" or "below" a second feature, etc., or similar descriptions appear, it may mean that the first and second features are in direct contact, or that the first and second features are in indirect contact through an intermediate medium. Moreover, the first feature being "above", "above" and "above" the second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. The first feature being "below", "below" and "below" the second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0050] It should be noted that if an element is referred to as being "fixed to" or "disposed on" another element, it may be directly on the other element or there may be a central element. If an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be a central element at the same time. If present, the terms "vertical", "horizontal", "upper", "lower", "left", "right" and similar expressions used in this application are for illustrative purposes only and do not represent the only implementation method.

[0051] Please refer to Figure 1-Figure 3 , a MEMS capacitive pressure sensor 100 provided in an embodiment of the present application includes:

[0052] Conductive substrate 1; along the direction of the plane where the conductive substrate 1 is located, the pressure sensor 100 includes a cavity area 11 and an edge area 10 surrounding the cavity area 11;

[0053] The first electrode layer 20 is formed on one side surface of the conductive substrate 1 and is located in the cavity area 11; the first electrode layer 20 includes a plurality of insulated annular first electrodes 12;

[0054] The pressure strain diaphragm 3 is located on a side of the first electrode layer 20 away from the conductive substrate 1;

[0055] The second electrode layer 30 is formed on the side of the pressure strain diaphragm 3 facing the first electrode layer 20 and is located in the cavity area 11; the second electrode layer 30 includes a plurality of insulated annular second electrodes 31;

[0056] An insulating layer 4 is formed between the conductive substrate 1 and the pressure strain diaphragm 3 and is located in the edge region 10;

[0057] In a direction from the center point of the plane where the conductive substrate 1 is located to the edge region 10 , the first electrodes 12 and the second electrodes 31 are arranged alternately and at intervals.

[0058] Specifically, the MEMS capacitive pressure sensor 100 provided in the present application may include a conductive substrate 1, a first electrode layer 20, a second electrode layer 30 and a pressure strain diaphragm 3 that are stacked in sequence along a direction perpendicular to the conductive substrate 1 included therein, that is, along its thickness direction, and an insulating layer 4 arranged between the conductive substrate 1 and the pressure strain diaphragm 3.

[0059] Among them, along the direction of the plane where the conductive substrate 1 is located, the pressure sensor 100 includes a cavity area 11 and an edge area 10 surrounding the cavity area 11, the conductive substrate 1 and the pressure strain diaphragm 3 of the MEMS capacitive pressure sensor 100 are arranged in the entire cavity area 11 and the entire edge area 10, the insulating layer 4 is only arranged in the edge area 10, and the first electrode 12 included in the first electrode layer 20 and the second electrode 31 included in the second electrode layer 30 are both only arranged in the cavity area 11.

[0060] The present application provides an optional arrangement of a first electrode layer 20 and a second electrode layer 30, wherein the first electrode layer 20 includes a plurality of annular first electrodes 12, and the second electrode layer 30 includes a plurality of annular second electrodes 31. The surrounding shapes of the first electrode 12 and the second electrode 31 can be arranged to be the same, for example, both are rectangular or both are circular, etc. The surrounding shape of the first electrode 12 and the second electrode 31 can be the same as the planar shape of the conductive substrate 1. Further, the arrangement of the orthographic projection of the first electrode 12 and the second electrode 31 on the plane where the conductive substrate 1 is located is that the first electrode 12 and the second electrode 31 are arranged alternately and at intervals along the direction from the center point of the plane where the conductive substrate 1 is located to the edge area 10, that is, along the direction of the plane where the conductive substrate 1 is located, there is an annular first electrode 12, an annular second electrode 31, an annular first electrode 12, and an annular second electrode 31, which are arranged in sequence from the center point of the cavity area 11 to the edge area 10; that is, along the direction from the center point of the cavity area 11 to the edge area 10, the adjacent first electrodes 12 and the second electrodes 31 are insulated, and there is a gap space between the adjacent first electrodes 12 and the second electrodes 31. The present application does not specifically limit the number of first electrodes 12 included in the first electrode layer 20, nor does it specifically limit the number of second electrodes 31 included in the second electrode layer 30. For example, the number of first electrodes 12 and the number of second electrodes 31 can be set to be the same as the number of second electrodes 31 according to needs.

[0061] In the MEMS capacitive pressure sensor 100 of the above structure provided in the present application, the conductive substrate 1 and the first electrode 12 are equivalent to constituting the first plate of the capacitor, the pressure strain diaphragm 3 and the second electrode 31 are equivalent to constituting the second plate of the capacitor, and the conductive substrate 1 and the pressure strain diaphragm 3 are arranged in parallel; when the user applies pressure to the pressure strain diaphragm 3 in the MEMS capacitive pressure sensor 100, the pressure strain diaphragm 3 is deformed and moves closer to the conductive substrate 1. Due to the reduction of the gap between the conductive substrate 1 and the pressure strain diaphragm 3, the capacitance between the two plates (the first plate and the second plate) can be increased.

[0062] In the MEMS capacitive pressure sensor 100 of the above structure provided in the present application, the conductive substrate 1, the pressure strain diaphragm 3 and the insulating layer 4 form a sealed cavity around the cavity area 11. The sealed cavity can optionally include air, or can be set to a vacuum according to needs, or filled with other gases according to needs, or filled with elastic materials according to needs. The present application does not specifically limit the substances included in the sealed cavity.

[0063] The MEMS capacitive pressure sensor 100 provided in the present application includes a conductive substrate 1; along the direction of the plane where the conductive substrate 1 is located, the pressure sensor 100 includes a cavity area 11 and an edge area 10 surrounding the cavity area 11; a first electrode layer 20 is formed on a side surface of the conductive substrate 1 and is located in the cavity area 11; the first electrode layer 20 includes a plurality of insulating annular first electrodes 12; a pressure strain diaphragm 3 is located on a side of the first electrode layer 20 away from the conductive substrate 1; a second electrode layer 30 is formed on a side of the pressure strain diaphragm 3 facing the first electrode layer 20 and is located in the cavity area 11; the second electrode layer 30 includes a plurality of insulating annular second electrodes 31; an insulating layer 4 is formed between the conductive substrate 1 and the pressure strain diaphragm 3 and is located in the edge area 10; along the center point in the plane where the conductive substrate 1 is located pointing to the edge In the direction of the area 10, the first electrode 12 and the second electrode 31 are alternately and spaced apart; it can be seen that the present application arranges a plurality of annular first electrodes 12 and a plurality of annular second electrodes 31, and alternately arranges them in the direction along the plane where the conductive substrate 1 is located, which is beneficial to increase the effective area between the capacitor plates composed of the conductive substrate 1 and the first electrode 12, and the capacitor plates composed of the pressure strain diaphragm 3 and the second electrode 31, which is beneficial to increase the overall sensitivity of the pressure sensor 100; and the first electrode 12 and the second electrode 31 are spaced apart in the direction of the plane where the conductive substrate 1 is located, which is beneficial to avoid the situation where the first electrode 12 and the second electrode 31 accidentally contact when pressure is applied to the surface of the pressure strain diaphragm 3, thereby helping to improve the linearity of the capacitive pressure sensor 100 and improve the pressure detection accuracy of the capacitive sensor.

[0064] Please continue to refer to Figure 1-Figure 3In some embodiments, the cavity region 11 includes a first cavity region 181 and a second cavity region 182 surrounding the first cavity region 181 ; the first electrode 12 and the second electrode 31 are both located in the second cavity region 182 .

[0065] Specifically, along the direction of the plane where the conductive substrate 1 is located, the cavity region 11 may specifically include a first cavity region 181 and a second cavity region 182, wherein the second cavity region 182 surrounds the first cavity region 181; based on this, the present application provides an optional implementation method in which the first electrode 12 and the second electrode 31 are both arranged in the second cavity region 182, that is, neither the first electrode 12 nor the second electrode 31 is arranged in the first cavity region 181.

[0066] Among them, the first cavity area 181 is equivalent to the central area of ​​the MEMS capacitive pressure sensor 100. The present application does not set electrodes in the central area of ​​the pressure sensor 100, but staggeredly sets annular protruding electrodes at a position far away from the central area of ​​the pressure sensor 100 (the second cavity area 182), that is, the annular first electrode 12 and the annular second electrode 31. This arrangement can increase the effective area between the capacitor plates (the first plate and the second plate) without increasing the height of the capacitor cavity (sealed cavity), thereby facilitating the improvement of the overall sensitivity of the capacitive pressure sensor 100. The height direction of the sealed cavity is the direction perpendicular to the plane where the conductive substrate 1 is located, that is, the direction in which the conductive substrate 1 points to the pressure strain diaphragm 3.

[0067] Please continue to refer to Figure 1-Figure 3 In some embodiments, it also includes a first metal pad 51 and a second metal pad 52 located in the edge area 10; the first metal pad 51 is formed on the side of the pressure strain diaphragm 3 away from the conductive substrate 1, and the second metal pad 52 is formed on the side of the insulating layer 4 away from the conductive substrate 1, and the second metal pad 52 is electrically connected to the conductive substrate 1 through the insulating layer 4.

[0068] Specifically, the MEMS capacitive pressure sensor 100 provided in the present application also includes a metal pad 5, specifically including a first metal pad 51 arranged on the side surface of the pressure strain diaphragm 3 away from the conductive substrate 1, and a second metal pad 52 arranged on the side surface of the insulating layer 4 away from the conductive substrate 1, wherein the pressure strain diaphragm 3 is not arranged in the area where the second metal pad 52 is located, so that at least one side surface of the second metal pad 52 away from the conductive substrate 1 can be exposed; further, the second metal pad 52 is electrically connected to the conductive substrate 1 via the through hole 2 in the insulating layer 4.

[0069] Based on this structure, the capacitance change between the first electrode plate and the second electrode plate can be led out through the pads (the first metal pad 51 and the second metal pad 52). When the user applies pressure to the pressure strain diaphragm 3 in the MEMS capacitive pressure sensor 100, the pressure strain diaphragm 3 is deformed and moves closer to the conductive substrate 1, and the gap between the conductive substrate 1 and the pressure strain diaphragm 3 is reduced, resulting in an increase in the capacitance between the two electrodes (the first electrode plate and the second electrode plate). The capacitance change signal is led out from the pad to detect the capacitance change using a micro capacitance detection circuit, thereby obtaining relevant pressure data after processing, and realizing the sensing of the received pressure by the MEMS capacitive pressure sensor 100.

[0070] Please continue to refer to Figure 1-Figure 3 In some embodiments, along the direction from the cavity area 11 to the edge area 10, the first metal pad 51 and the second metal pad 52 are respectively arranged on both sides of the cavity area 11. Such an arrangement is conducive to improving the accuracy of the pad for extracting the capacitance change signal sensed by the capacitive pressure sensor 100.

[0071] Please continue to refer to Figure 1-Figure 3 In some embodiments, in the direction from the conductive substrate 1 to the pressure strain diaphragm 3 , the sum of the size of the first electrode layer 20 and the size of the second electrode layer 30 is less than or equal to the size between the conductive substrate 1 and the pressure strain diaphragm 3 .

[0072] Specifically, along the thickness direction of the MEMS capacitive pressure sensor 100, that is, in the direction from the conductive substrate 1 to the pressure strain diaphragm 3, the sum of the size of the first electrode layer 20 and the size of the second electrode layer 30 can be selected to be smaller than the gap size between the conductive substrate 1 and the pressure strain diaphragm 3, or the sum of the size of the first electrode layer 20 and the size of the second electrode layer 30 can be selected to be exactly equal to the gap size between the conductive substrate 1 and the pressure strain diaphragm 3; that is, in the present application, the sum of the heights of the first electrode layer 20 and the second electrode layer 30 is not greater than the height of the sealed cavity.

[0073] Since the height of the electrode protrusion (the first electrode 12 and the second electrode 31) is too high, it will affect the deformation of the pressure strain diaphragm 3, resulting in a reduction in the range of the pressure sensor 100. Furthermore, if the electrode protrusion is too low, it will not increase the sensitivity. Therefore, in the technical solution provided in the present application, it is equivalent to a compromise to select the height of the electrode protrusion to be approximately half of the height of the sealing cavity, which is beneficial to ensure that the capacitive pressure sensor 100 has a better range and better detection sensitivity when the pressure strain diaphragm 3 in the capacitive pressure sensor 100 is subjected to pressure.

[0074] Please continue to refer to Figure 1-Figure 3In some embodiments, along the direction from the conductive substrate 1 to the pressure strain diaphragm 3 , the sizes of the first electrodes 12 are all the same, and the sizes of the second electrodes 31 are all the same.

[0075] Specifically, along the thickness direction of the capacitive pressure sensor 100, the sizes of the first electrodes 12 and the second electrodes 31 can be set to be the same; the sizes of the first electrodes 12 and the second electrodes 31 can be set to be the same along the thickness direction of the capacitive pressure sensor 100. This helps to reduce the difficulty of preparing the first electrode layer 20 and the second electrode layer 30.

[0076] In some embodiments, the material of at least one of the conductive substrate 1 and the pressure-strained diaphragm 3 includes low-resistance silicon. Specifically, low-resistance silicon can be selected to prepare the conductive substrate 1, and low-resistance silicon can also be selected to prepare the pressure-strained diaphragm 3; compared with traditional silicon wafers, low-resistance silicon wafers have lower resistivity, faster electron migration speed, and better conductivity. Therefore, the conductive substrate 1 and the pressure-strained diaphragm 3 prepared using low-resistance silicon also have good conductivity.

[0077] The use of low-resistance silicon to prepare the conductive substrate 1 and the pressure-strained diaphragm 3 is only an optional implementation provided in the present application. If necessary, other materials with good conductive properties can also be selected to prepare the conductive substrate 1 and the pressure-strained diaphragm 3.

[0078] In some embodiments, the material of at least one of the first electrode 12 and the second electrode 31 includes at least one of gold and aluminum. Specifically, metal gold or metal aluminum can be selected to prepare the first electrode 12, and metal gold or metal aluminum can be selected to prepare the second electrode 31; in addition, other metal materials with good electrical conductivity can also be selected to prepare the first electrode 12 and the second electrode 31. That is. The electrode material is not limited to aluminum or gold, and can also be some other metal materials or alloy materials with good electrical conductivity. The first electrode 12 and the second electrode 31 can be prepared using the same material.

[0079] In addition, the present application also provides an optional implementation mode in which the first electrode 12 and the second electrode 31 can also be made of low-resistance silicon.

[0080] Based on this, for the MEMS capacitive pressure sensor 100 provided in the present application, an optional structure is provided, which includes a fixed lower plate, a metal lead-out structure and a pressure strain diaphragm 3 component; wherein the fixed lower plate includes a low-resistance silicon substrate (conductive substrate 1), a dielectric insulating layer 4, a low-resistance silicon open cavity area (sealed cavity 11) and a homogeneous silicon material annular protrusion (first electrode 12), and the low-resistance silicon substrate and the homogeneous silicon material annular protrusion constitute the first plate of the capacitor; the metal lead-out structure includes a through hole 2, a metal pad 5 (a first metal pad 51 and a second metal pad 52); wherein the "through hole" here is formed in the insulating layer 4 and is located on the side of the second metal pad 52 facing the low-resistance silicon substrate, and can be filled with a conductive material; the pressure strain diaphragm 3 component includes a silicon material (e.g., low-resistance silicon) elastic strain film (pressure strain diaphragm 3) and an annular protrusion (second electrode 31), which together constitute the second plate of the capacitor. The low-resistance silicon substrate and the annular protrusions (the first electrode 12 and the second electrode 31) on the pressure strain diaphragm 3 are arranged alternately, and the orthographic projections of the annular protrusion structures (the first electrode 12 and the second electrode 31) on the plane where the low-resistance silicon substrate is located do not overlap, and the gap between the orthographic projections of the staggered patterns is greater than zero. The thickness of the staggered annular protrusion structure in the thickness direction is approximately half of the height of the cavity (sealed cavity).

[0081] The MEMS capacitive pressure sensor 100 provided in the present application has a pressure strain diaphragm 3 that operates in a small deflection range. During operation, the pressure strain diaphragm 3 is linearly close to the low-resistance silicon substrate, thereby causing a change in the capacitance between the plates, thereby achieving pressure measurement; the annular protrusions that are staggered away from the center of the device increase the effective area between the capacitor plates without increasing the height of the capacitor cavity, thereby improving the overall sensitivity of the device.

[0082] It can be seen that the pressure strain diaphragm 3 of the present application is staggered with the annular protrusion structure on the low-resistance silicon substrate, which will not have a negative impact on the cavity height under the condition of locally reducing the distance between the capacitor plates. The upper and lower staggered annular protrusions of the present application cooperate with each other to increase the effective area between the first and second plates of the capacitor, thereby increasing the sensitivity of the device. The process of the present application is simple and easy to implement, and the electrode material is not limited to aluminum or gold, and can be some other metal materials or alloy materials.

[0083] Please combine Figure 1-Figure 3 Reference Figure 4-Figure 7 Based on the same inventive concept, the present application also provides a method for preparing a MEMS capacitive pressure sensor 100, comprising steps 101 to 111, wherein:

[0084] Step 101, providing a conductive substrate 1; along the direction of the plane where the conductive substrate 1 is located, the pressure sensor 100 includes a cavity area 11 and an edge area 10 surrounding the cavity area 11;

[0085] Step 102, depositing an insulating layer 4 on one side surface of the conductive substrate 1;

[0086] Step 103, etching a portion of the insulating layer 4 in the cavity area 11 to form a plurality of insulating annular first grooves;

[0087] Step 104, preparing a first electrode 12 in the first groove to form a first electrode layer 20;

[0088] Step 105, etching another portion of the insulating layer 4 in the cavity area 11;

[0089] Step 106, depositing an insulating layer 4 on the surface of the conductive substrate 1 facing the first electrode layer 20;

[0090] Step 107, etching a portion of the insulating layer 4 in the cavity area 11 to form a plurality of insulating annular second grooves; the first grooves and the second grooves are alternately and spaced from the center point of the plane where the conductive substrate 1 is located to the edge area 10;

[0091] Step 108, preparing a second electrode 31 in the second groove to form a second electrode layer 30;

[0092] Step 109, preparing a pressure strain diaphragm 3 on a surface of the second electrode layer 30 away from the first electrode layer 20;

[0093] Step 110, etching a portion of the pressure strain diaphragm 3 in the cavity region 11 along the direction of the pressure strain diaphragm 3 toward the conductive substrate 1 to form an etching hole 32 penetrating the pressure strain diaphragm 3;

[0094] Step 111 , etching the insulating layer 4 in the cavity area 11 based on the etched hole, and filling the etched hole 32 .

[0095] Furthermore, the method for preparing the MEMS capacitive pressure sensor 100 further includes steps 112 and 113 performed after step 111, wherein:

[0096] Step 112, etching a portion of the pressure strained diaphragm 3 and the insulating layer 4 in the edge region 10 along the direction of the pressure strained diaphragm 3 toward the conductive substrate 1, to form a through hole 49 penetrating the pressure strained diaphragm 3 and the insulating layer 4;

[0097] Step 113, prepare a first metal pad 51 on the surface of the pressure strain diaphragm 3 on the side away from the conductive substrate 1, and prepare a second metal pad 52 on the surface of the insulating layer 4 where the through hole is located on the side away from the conductive substrate 1; the second metal pad 52 is electrically connected to the conductive substrate 1 through the through hole 49 where the insulating layer 4 is located.

[0098] Before step 113 , the following step may be further included: using a conductive material to fill the portion of the through hole 2 corresponding to the insulating layer 4 in the through hole 49 .

[0099] Based on this, a method (process flow) for preparing a MEMS capacitive pressure sensor 100 is provided, which may be selected in a specific embodiment, including steps 201 to 204, wherein:

[0100] Step 201, first prepare a low-resistance silicon wafer (conductive substrate 1), vapor-deposit a dielectric insulating layer 4 such as SiO2 (silicon dioxide), the insulating layer 4 is used as a sacrificial layer, and then the insulating layer 4 is etched, and then a ring-shaped protrusion (first electrode 12) is grown on the low-resistance silicon substrate, and then the insulating layer 4 is etched to form a cavity structure, such as Figure 4 As shown, this step completes the required process processing for the substrate and completes the preparation of the first electrode plate of the capacitor.

[0101] Step 202, further, a dielectric insulating layer 4 is deposited on the substrate. After the insulating layer 4 reaches a certain thickness, a photolithography is performed to open the annular groove, and then a layer of low-resistance silicon material is deposited to realize the preparation of the convex structure (second electrode 31) on the pressure strain diaphragm 3. Figure 5 As shown, this step completes the process required for the pressure strain diaphragm 3 and completes the preparation of the second electrode plate of the capacitor.

[0102] Step 203, further, the pressure strain diaphragm 3 prepared in step 202 is etched to open an etched hole 32 on the diaphragm, and then the sacrificial layer is etched to release the capacitor cavity. After the cavity is released, it is dried, and then the etched hole 32 is filled by a deposition process. The process is as follows: Figure 6 As shown, this step completes the release of the cavity under the pressure-strained film.

[0103] Step 204, further, as Figure 7 As shown, one side of the pressure strain diaphragm 3 is etched, a window is opened in the top material, and then the dielectric insulating material is etched (to form a through hole 49). After the etching is completed, a layer of conductive material is deposited in the etched channel (through hole 2) to lead out the electrode, and finally the pad 5 is formed by metal sputtering and removing the excess metal layer. This step completes the process required for the electrode of the capacitor plate and completes the preparation of the electrode.

[0104] In the structure of the present application, the annular protrusions of the substrate and the annular protrusions of the pressure strain diaphragm 3 are staggered, that is, the first electrode 12 and the second electrode 31, which increase the effective area between the two capacitor plates. At the same time, their projections on the plane where the conductive substrate 1 is located do not overlap, and the projection gap is greater than 0, and the thickness of the annular protrusion structure is approximately half of the capacitor gap (the height of the sealed cavity). As a result, the pressure strain diaphragm 3 will not collide when it approaches the substrate (conductive substrate 1), that is, the first electrode 12 and the second electrode 31 will not collide. Therefore, when the sensitivity of the MEMS capacitive pressure sensor 100 is increased, there is no need to increase the height of the capacitor gap.

[0105] The working process of the MEMS capacitive pressure sensor 100 of the present application is: when pressure is applied to the pressure strain diaphragm 3, the diaphragm is deformed and moves closer to the substrate. The reduction in the gap leads to an increase in the capacitance between the two plates. The capacitance change signal can be drawn out from the pad, and the capacitance change is detected by a micro-capacitance detection circuit. After processing, pressure data can be obtained.

[0106] The capacitive effect utilized in this application combines the miniaturization characteristics of micro-electromechanical systems (MEMS) with the low temperature drift and low power consumption of the capacitive pressure sensor 100, and has the characteristics of high sensitivity, low temperature drift, wide temperature range operation, low power consumption, and strong portability.

[0107] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0108] The above-described embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be construed as limiting the scope of the patent application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent application shall be subject to the attached claims.

Claims

1. A MEMS capacitive pressure sensor, characterized in that: include: Conductive substrate; Along the direction of the plane where the conductive substrate is located, the pressure sensor includes a cavity area and an edge area surrounding the cavity area; A first electrode layer is formed on one side surface of the conductive substrate and is located in the cavity area; the first electrode layer includes a plurality of insulated annular first electrodes; A pressure strain diaphragm, located on a side of the first electrode layer away from the conductive substrate; A second electrode layer is formed on a side of the pressure strain diaphragm facing the first electrode layer and is located in the cavity area; the second electrode layer includes a plurality of insulated annular second electrodes; an insulating layer formed between the conductive substrate and the pressure-strained diaphragm and located in the edge region; In a direction from a center point in a plane where the conductive substrate is located to the edge region, the first electrodes and the second electrodes are arranged alternately and at intervals.

2. The MEMS capacitive pressure sensor according to claim 1, characterized in that: The cavity area includes a first cavity area and a second cavity area surrounding the first cavity area; The first electrode and the second electrode are both located in the second cavity region.

3. The MEMS capacitive pressure sensor according to claim 1 or 2, characterized in that: Also included is a first metal pad and a second metal pad located in the edge region; The first metal pad is formed on a side of the pressure strain diaphragm away from the conductive substrate, the second metal pad is formed on a side of the insulating layer away from the conductive substrate, and the second metal pad is electrically connected to the conductive substrate through the insulating layer.

4. The MEMS capacitive pressure sensor according to claim 3, characterized in that: In a direction from the cavity area to the edge area, the first metal pad and the second metal pad are respectively arranged on two sides of the cavity area.

5. The MEMS capacitive pressure sensor according to claim 1 or 2, characterized in that: In a direction from the conductive substrate to the pressure-strained diaphragm, a sum of a size of the first electrode layer and a size of the second electrode layer is less than or equal to a size between the conductive substrate and the pressure-strained diaphragm.

6. The MEMS capacitive pressure sensor according to claim 5, characterized in that: In a direction from the conductive substrate to the pressure strain diaphragm, the sizes of the first electrodes are all the same, and the sizes of the second electrodes are all the same.

7. The MEMS capacitive pressure sensor according to claim 1 or 2, characterized in that: At least one of the conductive substrate and the pressure-strained diaphragm is made of a material including low-resistance silicon.

8. The MEMS capacitive pressure sensor according to claim 1 or 2, characterized in that: The material of at least one of the first electrode and the second electrode includes at least one of gold and aluminum.

9. A method for preparing a MEMS capacitive pressure sensor, characterized in that: include: providing a conductive substrate; Along the direction of the plane where the conductive substrate is located, the pressure sensor includes a cavity area and an edge area surrounding the cavity area; Depositing an insulating layer on one surface of the conductive substrate; Etching a portion of the insulating layer in the cavity area to form a plurality of insulatingly arranged annular first grooves; In the first groove, a first electrode is prepared to form a first electrode layer; etching another portion of the insulating layer in the cavity region; Depositing an insulating layer on a surface of the conductive substrate facing the first electrode layer; Etching a portion of the insulating layer in the cavity area to form a plurality of insulating annular second grooves; the first grooves and the second grooves are alternately and spaced apart in a direction from a center point in a plane where the conductive substrate is located to the edge area; In the second groove, a second electrode is prepared to form a second electrode layer; A pressure strain diaphragm is prepared on a surface of the second electrode layer on a side away from the first electrode layer; Etching a portion of the pressure-strained diaphragm in the cavity region in a direction from the pressure-strained diaphragm toward the conductive substrate to form an etching hole penetrating the pressure-strained diaphragm; The insulating layer in the cavity area is etched based on the etched hole, and the etched hole is filled.

10. The method for preparing a MEMS capacitive pressure sensor according to claim 9, characterized in that: Also includes: Etching a portion of the pressure-strained diaphragm and the insulating layer in the edge region in a direction from the pressure-strained diaphragm toward the conductive substrate to form a through hole penetrating the pressure-strained diaphragm and the insulating layer; A first metal pad is prepared on a surface of the pressure strain diaphragm away from the conductive substrate, and a second metal pad is prepared on a surface of the insulating layer where the through hole is located away from the conductive substrate; the second metal pad is electrically connected to the conductive substrate through the through hole where the insulating layer is located.

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