Membrane-based capacitive pressure sensor and method of manufacturing the same

Abstract

The application relates to a MEMS capacitive pressure sensor and a preparation method thereof, and relates to the technical field of microelectronics; the pressure sensor comprises a conductive substrate; in the direction of the plane where the conductive substrate is located, the pressure sensor comprises a cavity region and an edge region surrounding the cavity region; a first electrode layer is formed on the surface of the conductive substrate and is located in the cavity region; the first electrode layer comprises a plurality of annular first electrodes which are insulatively arranged; 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 region; the second electrode layer comprises a plurality of annular second electrodes which are insulatively arranged; an insulating layer is formed between the conductive substrate and the pressure strain diaphragm and is located in the edge region; in the direction from the center point in the plane where the conductive substrate is located to the edge region, the first electrodes and the second electrodes are alternately and spacedly arranged; the problem that the first electrodes and the second electrodes are miscontacted when the pressure sensor is used can be avoided.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of microelectronics, in particular to a MEMS capacitive pressure sensor and a preparation method thereof. BACKGROUND

[0002] The monitoring demand for pressure in social production is very huge, especially in the fields of industry and automobile. Micro-electro-mechanical system (MEMS) pressure sensors have good industrial application due to their small size, high performance, strong reliability, low cost, easy mass production, and strong portability, and are widely used in consumer electronics, industrial control, aerospace, medical devices, and automobile manufacturing, and are the most successful case of MEMS sensor marketization.

[0003] The mainstream technology of the current MEMS pressure sensor can be divided into piezoresistive and capacitive. The piezoresistive utilizes the piezoresistive effect, and when the piezoresistive material is subjected to external pressure, the resistance thereof will change, thereby realizing the detection of pressure. The capacitive pressure sensor is composed of a strain diaphragm, and the capacitance value of the capacitor changes with pressure, thereby realizing the detection of pressure. The piezoresistive pressure sensor has the advantage of high linearity compared with the capacitive pressure sensor, but its biggest disadvantage is temperature drift, because the piezoresistive resistor of the piezoresistive pressure sensor is made of silicon doping, and the resistance value thereof is easily affected by temperature. The capacitive pressure sensor has the advantages of low power consumption, high sensitivity, and excellent temperature characteristics, and has great advantages when working in a wide temperature range. Since the pressure strain diaphragm as a capacitor plate is not parallel to the other capacitor plate when deformed under pressure, the linearity of the capacitive pressure sensor is poorer than that of the piezoresistive pressure sensor.

[0004] Therefore, it is urgent to provide a capacitive pressure sensor with good linearity. SUMMARY

[0005] Therefore, it is urgent to provide a capacitive pressure sensor with good linearity.

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

[0007] A conductive substrate; in the direction of the plane where the conductive substrate is located, the pressure sensor comprises a cavity region and an edge region surrounding the cavity region;

[0008] A first electrode layer is formed on one side surface of the conductive substrate and located in the cavity region; the first electrode layer comprises a plurality of annular first electrodes arranged in insulation;

[0009] a pressure-strained diaphragm located on a side of the first electrode layer away from the conductive substrate;

[0010] a second electrode layer formed on a side of the pressure-strained diaphragm facing the first electrode layer and located in the cavity region; the second electrode layer comprises a plurality of annular second electrodes arranged in isolation;

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

[0012] The first electrodes and the second electrodes are alternately and spacedly arranged in a direction from a center point in a plane in which the conductive substrate is located to the edge region.

[0013] In one of the embodiments, the cavity region comprises a first cavity region and a second cavity region surrounding the first cavity region.

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

[0015] In one of the embodiments, it further comprises 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-strained 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 with the conductive substrate through the insulating layer.

[0017] In one of the embodiments, the first metal pad and the second metal pad are separately arranged on two sides of the cavity region in a direction from the cavity region to the edge region.

[0018] In one of the embodiments, 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 of the embodiments, in 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, a material for preparing at least one of the conductive substrate and the pressure-strained diaphragm comprises low-resistance silicon.

[0021] In one of the embodiments, a material for preparing at least one of the first electrodes and the second electrodes comprises at least one of gold and aluminum.

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

[0023] providing a conductive substrate; the pressure sensor comprises a cavity region and an edge region surrounding the cavity region in the direction of the plane in which the conductive substrate lies;

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

[0025] etching a portion of the insulating layer of the cavity region to form a plurality of insulatively arranged annular first grooves;

[0026] manufacturing a first electrode in the first grooves to form a first electrode layer;

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

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

[0029] etching a portion of the insulating layer of the cavity region to form a plurality of insulatively arranged annular second grooves; the first grooves and the second grooves are alternately and spacedly arranged in the direction of the edge region from the center point in the plane in which the conductive substrate lies;

[0030] manufacturing a second electrode in the second grooves to form a second electrode layer;

[0031] manufacturing a pressure strain diaphragm on the side surface of the second electrode layer away from the first electrode layer;

[0032] etching a portion of the pressure strain diaphragm of the cavity region in the direction of the conductive substrate to form an etching hole penetrating through the pressure strain diaphragm;

[0033] etching the insulating layer of the cavity region based on the etching hole, and filling the etching hole.

[0034] In one embodiment, the method further comprises:

[0035] etching a portion of the pressure strain diaphragm of the edge region and the insulating layer in the direction of the conductive substrate to form a through hole penetrating through the pressure strain diaphragm and the insulating layer;

[0036] manufacturing a first metal pad on the side surface of the pressure strain diaphragm away from the conductive substrate, and manufacturing a second metal pad on the side surface of the insulating layer away from the conductive substrate at the through hole; the second metal pad is electrically connected with the conductive substrate through the through hole of the insulating layer.

[0037] The MEMS capacitive pressure sensor and the preparation method thereof provided in the application, the MEMS capacitive pressure sensor comprises a conductive substrate; in the direction of the plane where the conductive substrate is located, the pressure sensor comprises a cavity region and an edge region surrounding the cavity region; a first electrode layer is formed on one side surface of the conductive substrate and is located in the cavity region; the first electrode layer comprises a plurality of annular first electrodes which are insulated; 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 region; the second electrode layer comprises a plurality of annular second electrodes which are insulated; an insulating layer is formed between the conductive substrate and the pressure strain diaphragm and is located in the edge region; the first electrodes and the second electrodes are alternately and spacedly arranged in the direction from the center point in the plane where the conductive substrate is located to the edge region; it can be seen that, by arranging the plurality of annular first electrodes and the plurality of annular second electrodes, the effective area between the capacitor plate composed of the conductive substrate and the first electrode and the capacitor plate composed of the pressure strain diaphragm and the second electrode is increased in the direction of the plane where the conductive substrate is located, which is beneficial to increase the overall sensitivity of the pressure sensor; and the first electrodes and the second electrodes are spacedly arranged in the direction of the plane where the conductive substrate is located, which is beneficial to avoid the miscontacting of the first electrodes and the second electrodes when the pressure is applied to the surface of the pressure strain diaphragm, thereby improving the linearity of the capacitive pressure sensor and the pressure detection accuracy of the capacitive sensor. BRIEF DESCRIPTION OF DRAWINGS

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

[0039] Figure 2 A cross-sectional view of the MEMS capacitive pressure sensor provided in the embodiment of the application; Figure 1

[0040] Figure 3 A partial perspective view of the MEMS capacitive pressure sensor provided in the embodiment of the application;

[0041] Figure 4 A preparation flowchart of the first electrode layer in the MEMS capacitive pressure sensor provided in the embodiment of the application; Figure 1

[0042] A preparation flowchart of the second electrode layer and the pressure strain diaphragm in the MEMS capacitive pressure sensor provided in the embodiment of the application; Figure 5 Figure 1 A preparation flowchart of the sealed cavity in the MEMS capacitive pressure sensor provided in the embodiment of the application;

[0043] Figure 6 Figure 1 A preparation flowchart of the sealed cavity in the MEMS capacitive pressure sensor provided in the embodiment of the application;

[0044] ​​​Figure 7 A preparation flow chart of a first metal pad and a second metal pad is provided in the embodiments of the present application. Figure 1 A preparation flow chart of a first metal pad and a second metal pad is provided in the embodiments of the present application. DETAILED DESCRIPTION

[0045] In order to make the above objectives, characteristics and advantages of the present application more apparent, specific embodiments of the present application will be described in detail below with reference to the drawings. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present application. However, the present application can be practiced in a number of ways other than those specifically described herein, and the present application is not limited to the specific embodiments described below. It is to be understood that other embodiments can be employed and that structural and functional modifications can be made without departing from the scope of the present application.

[0046] In the description of the present application, it should be understood that, if there are terms such as "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. appear, these terms indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the purpose of facilitating the description of the present application and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application.

[0047] In addition, if the terms "first", "second" appear, these terms are only for the purpose of description, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features limited by "first", "second" can explicitly or implicitly include at least one of the features. In the description of the present application, if the term "multiple" appears, the meaning of "multiple" is at least two, such as two, three, etc., unless otherwise specifically limited.

[0048] In the present application, unless otherwise specifically defined and limited, if the terms "mount", "connect", "connect", "fix" and the like appear, these terms should be broadly understood. For example, it can be fixedly connected, or it can be detachably connected, or it can be integrated; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium; it can be the internal communication of two elements or the interaction relationship between two elements, unless otherwise specifically limited. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0049] In the present application, unless specifically defined and limited otherwise, if there is a description of a first feature on or above or below a second feature, it can mean that the first and second features are in direct contact, or the first and second features are indirectly in contact through an intermediate medium. Moreover, the first feature can be above or above and above the second feature, or it can only mean that the first feature is higher in horizontal height than the second feature. The first feature can be below or below and below the second feature, or it can only mean that the first feature is lower in horizontal height than the second feature.

[0050] It should be noted that if an element is referred to as being "fixed" or "set" on another element, it can be directly on the other element or there can be an intermediate element. If an element is considered to be "connected" to another element, it can be directly connected to the other element or there can be an intermediate element. If present, the terms "vertical", "horizontal", "up", "down", "left", "right" and similar expressions used in the present application are only for the purpose of illustration and do not mean the only implementation.

[0051] Please refer to Figures 1-3 An embodiment of the present application provides a MEMS capacitive pressure sensor 100, comprising:

[0052] A conductive substrate 1; in the direction of the plane in which the conductive substrate 1 is located, the pressure sensor 100 comprises a cavity region 11 and an edge region 10 surrounding the cavity region 11;

[0053] A first electrode layer 20 is formed on one side surface of the conductive substrate 1 and located in the cavity region 11; the first electrode layer 20 comprises a plurality of annular first electrodes 12 arranged in isolation;

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

[0055] A second electrode layer 30 is formed on the side of the pressure strain diaphragm 3 facing the first electrode layer 20 and located in the cavity region 11; the second electrode layer 30 comprises a plurality of annular second electrodes 31 arranged in isolation;

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

[0057] In the direction from the center point in the plane in which the conductive substrate 1 is located to the edge region 10, the first electrodes 12 and the second electrodes 31 are alternately and spacedly arranged.

[0058] Specifically, the MEMS capacitive pressure sensor 100 provided by the present application can sequentially comprise, in the direction perpendicular to the conductive substrate 1 included therein, i.e. in the thickness direction thereof, the conductive substrate 1, the first electrode layer 20, the second electrode layer 30 and the pressure strain diaphragm 3 arranged in a stacked manner, and the insulating layer 4 arranged between the conductive substrate 1 and the pressure strain diaphragm 3.

[0059] In the direction of the plane in which the conductive substrate 1 is located, the pressure sensor 100 comprises the cavity region 11 and the edge region 10 surrounding the cavity region 11, the conductive substrate 1 and the pressure strain diaphragm 3 of the MEMS capacitive pressure sensor 100 are arranged in the entire cavity region 11 and the entire edge region 10, the insulating layer 4 is arranged only in the edge region 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 arranged only in the cavity region 11.

[0060] The present application provides a selectable arrangement mode of the first electrode layer 20 and the second electrode layer 30, wherein the first electrode layer 20 comprises a plurality of annular first electrodes 12, and the second electrode layer 30 comprises a plurality of annular second electrodes 31, the annular shapes of the first electrodes 12 and the second electrodes 31 can be the same, for example, both are rectangular or both are circular, etc., and the annular shapes of the first electrodes 12 and the second electrodes 31 can be the same as the planar shape of the conductive substrate 1. Further, the arrangement mode of the orthographic projection of the first electrodes 12 and the second electrodes 31 in the plane of the conductive substrate 1 is that, in the direction of the center point of the plane of the conductive substrate 1 pointing to the edge region 10, the first electrodes 12 and the second electrodes 31 are arranged alternately and spaced apart, i.e. in the direction of the plane of the conductive substrate 1, one annular first electrode 12, one annular second electrode 31, one annular first electrode 12, one annular second electrode 31 are arranged in sequence from the center point of the cavity region 11 to the edge region 10; i.e. in the direction of the center point of the cavity region 11 pointing to the edge region 10, the first electrode 12 and the second electrode 31 arranged adjacently are insulated, and there is a gap space between the first electrode 12 and the second electrode 31 arranged adjacently. The present application does not make specific limitation on the number of the first electrodes 12 included in the first electrode layer 20, nor on the number of the second electrodes 31 included in the second electrode layer 30, for example, the number of the first electrodes 12 and the number of the second electrodes 31 can be selected to be the same according to requirements.

[0061] The MEMS capacitive pressure sensor 100 provided in the application comprises the conductive substrate 1, the cavity area 11 and the edge area 10 surrounding the cavity area 11 in the direction of the plane where the conductive substrate 1 is located, the first electrode layer 20 formed on one side surface of the conductive substrate 1 and located in the cavity area 11, the first electrode layer 20 comprising a plurality of annular first electrodes 12 insulated from each other, the pressure strain diaphragm 3 located on the side of the first electrode layer 20 away from the conductive substrate 1, the second electrode layer 30 formed on the side of the pressure strain diaphragm 3 facing the first electrode layer 20 and located in the cavity area 11, the second electrode layer 30 comprising a plurality of annular second electrodes 31 insulated from each other, and the insulating layer 4 formed between the conductive substrate 1 and the pressure strain diaphragm 3 and located in the edge area 10. In the MEMS capacitive pressure sensor 100 provided in the application, the conductive substrate 1 and the first electrode 12 constitute the first plate of the capacitor, the pressure strain diaphragm 3 and the second electrode 31 constitute the second plate of the capacitor, and the conductive substrate 1 and the pressure strain diaphragm 3 are arranged in parallel. When a user applies pressure to the pressure strain diaphragm 3 in the MEMS capacitive pressure sensor 100, the pressure strain diaphragm 3 deforms and moves closer to the conductive substrate 1, and the capacitance between the two plates (the first plate and the second plate) increases due to the decrease of the gap between the conductive substrate 1 and the pressure strain diaphragm 3.

[0062] In the MEMS capacitive pressure sensor 100 provided in the application, the conductive substrate 1, the pressure strain diaphragm 3 and the insulating layer 4 surround the cavity area 11 to form a sealed cavity. The sealed cavity can contain air, or be vacuumized according to requirements, or be filled with other gases according to requirements, or be filled with elastic materials according to requirements. The application does not make specific limitations on the substances contained in the sealed cavity.

[0063] The MEMS capacitive pressure sensor 100 provided in the application comprises the conductive substrate 1, the cavity area 11 and the edge area 10 surrounding the cavity area 11 in the direction of the plane where the conductive substrate 1 is located, the first electrode layer 20 formed on one side surface of the conductive substrate 1 and located in the cavity area 11, the first electrode layer 20 comprising a plurality of annular first electrodes 12 insulated from each other, the pressure strain diaphragm 3 located on the side of the first electrode layer 20 away from the conductive substrate 1, the second electrode layer 30 formed on the side of the pressure strain diaphragm 3 facing the first electrode layer 20 and located in the cavity area 11, the second electrode layer 30 comprising a plurality of annular second electrodes 31 insulated from each other, and the insulating layer 4 formed between the conductive substrate 1 and the pressure strain diaphragm 3 and located in the edge area 10. In the MEMS capacitive pressure sensor 100 provided in the application, the conductive substrate 1 and the first electrode 12 constitute the first plate of the capacitor, the pressure strain diaphragm 3 and the second electrode 31 constitute the second plate of the capacitor, and the conductive substrate 1 and the pressure strain diaphragm 3 are arranged in parallel. When a user applies pressure to the pressure strain diaphragm 3 in the MEMS capacitive pressure sensor 100, the pressure strain diaphragm 3 deforms and moves closer to the conductive substrate 1, and the capacitance between the two plates (the first plate and the second plate) increases due to the decrease of the gap between the conductive substrate 1 and the pressure strain diaphragm 3.

[0064] Please continue to refer to Figures 1-3In some embodiments, the cavity region 11 comprises 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, in the direction of the plane where the conductive substrate 1 is located, the cavity region 11 specifically comprises 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 application provides an alternative embodiment that 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] The first cavity region 181 is equivalent to the central region of the MEMS capacitive pressure sensor 100, and the application does not arrange electrodes in the central region of the pressure sensor 100, but arranges the annular protruding electrodes, that is, the annular first electrode 12 and the annular second electrode 31, staggered at a position (the second cavity region 182) away from the central region of the pressure sensor 100. This arrangement can increase the effective area between the capacitive plates (the first plate and the second plate) without increasing the height of the capacitive cavity (the sealed cavity), thereby facilitating the improvement of the overall sensitivity of the capacitive pressure sensor 100. The height direction of the sealed cavity, that 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 Figures 1-3 In some embodiments, the first metal pad 51 and the second metal pad 52 are arranged in the edge region 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 by the application further comprises a metal pad 5, specifically comprising 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 region where the second metal pad 52 is located is not arranged with the pressure strain diaphragm 3, so that at least the 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 through the through hole 2 in the insulating layer 4.

[0069] Based on the structure, the capacitance change between the first electrode plate and the second electrode plate can be led out through the bonding pads (the first metal bonding pad 51 and the second metal bonding pad 52). When a user applies pressure to the pressure strain diaphragm 3 in the MEMS capacitive pressure sensor 100, the pressure strain diaphragm 3 deforms to the side of the conductive substrate 1, the gap between the conductive substrate 1 and the pressure strain diaphragm 3 is reduced, the capacitance between the two electrode plates (the first electrode plate and the second electrode plate) is increased, and the capacitance change signal is led out by the bonding pads. The capacitance change is detected by a small capacitance detection circuit, and relevant pressure data is obtained through processing, so that the MEMS capacitive pressure sensor 100 senses the received pressure size.

[0070] Please continue to refer to Figures 1-3 In some embodiments, the first metal bonding pad 51 and the second metal bonding pad 52 are arranged on the two sides of the cavity area 11 in the direction of the edge area 10. In this way, the bonding pads can improve the accuracy of leading out the capacitance change signal sensed by the capacitive pressure sensor 100.

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

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

[0073] If the height of the electrode protrusion (the first electrode 12 and the second electrode 31) is too high, it will affect the deformation amount of the pressure strain diaphragm 3, resulting in a decrease in the range of the pressure sensor 100. Moreover, if the electrode protrusion is too low, it cannot increase the sensitivity. Therefore, in the technical solution provided in the present application, the height of the electrode protrusion is selected to be about half of the height of the sealed cavity, which is beneficial to ensuring that the capacitive pressure sensor 100 has good range and good detection sensitivity when the pressure strain diaphragm 3 in the capacitive pressure sensor 100 is subjected to pressure.

[0074] Please continue to refer to Figures 1-3In some embodiments, the first electrodes 12 have the same size in the direction pointing to the pressure strain diaphragm 3 along the conductive substrate 1, and the second electrodes 31 have the same size in the direction pointing to the pressure strain diaphragm 3 along the conductive substrate 1.

[0075] Specifically, in the thickness direction of the capacitive pressure sensor 100, the size of each first electrode 12 can be selected to be the same, and the size of each second electrode 31 can be selected to be the same; and further, the size of each first electrode 12 and the size of each second electrode 31 in the thickness direction of the capacitive pressure sensor 100 can be selected to be the same. In this way, the preparation difficulty of the first electrode layer 20 and the second electrode layer 30 can be reduced.

[0076] In some embodiments, the material for preparing at least one of the conductive substrate 1 and the pressure strain diaphragm 3 includes low-resistance silicon. Specifically, the conductive substrate 1 can be prepared by using low-resistance silicon, and the pressure strain diaphragm 3 can also be prepared by using low-resistance silicon; compared with a traditional silicon wafer, a low-resistance silicon wafer has a lower resistivity, a faster electron migration speed, and better conductive performance, and therefore, the conductive substrate 1 and the pressure strain diaphragm 3 prepared by using low-resistance silicon also have good conductive performance.

[0077] The conductive substrate 1 and the pressure strain diaphragm 3 prepared by using low-resistance silicon are only one optional implementation provided by the present application, and in the case of demand, other materials with good conductive performance can also be selected to prepare the conductive substrate 1 and the pressure strain diaphragm 3.

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

[0079] In addition, the present application also provides an optional implementation, in which the first electrodes 12 and the second electrodes 31 can also be prepared by using low-resistance silicon.

[0080] Based on this, for the MEMS capacitive pressure sensor 100 provided by the application, an alternative structure is provided, which comprises a fixed lower electrode plate, a metal lead-out structure and a pressure strain diaphragm 3 assembly; wherein the fixed lower electrode plate comprises a low-resistance silicon substrate (conductive substrate 1), a dielectric insulation layer 4, a low-resistance silicon cavity opening area (sealed cavity 11) and a homogenous silicon material ring-shaped protrusion (first electrode 12), and the low-resistance silicon substrate and the homogenous silicon material ring-shaped protrusion constitute a capacitive first electrode plate; the metal lead-out structure comprises a through hole 2 and a metal pad 5 (first metal pad 51 and second metal pad 52); wherein the through hole is formed in the insulation layer 4 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 assembly comprises a silicon material (for example, low-resistance silicon) elastic strain film (pressure strain diaphragm 3) and a ring-shaped protrusion (second electrode 31), which constitute a capacitive second electrode plate. Wherein the low-resistance silicon substrate and the ring-shaped protrusions (first electrode 12 and second electrode 31) on the pressure strain diaphragm 3 are staggered, the ring-shaped protrusion structures (first electrode 12 and second electrode 31) do not overlap in the orthographic projection on the plane of the low-resistance silicon substrate, and the gap between the orthographic projections is greater than zero. The thickness of the staggered ring-shaped protrusion structure in the thickness direction is about one half of the height of the cavity (sealed cavity).

[0081] The MEMS capacitive pressure sensor 100 provided by the application works in a small deflection range, and the pressure strain diaphragm 3 linearly approaches the low-resistance silicon substrate during work, thereby causing a change in the capacitance between the electrode plates and realizing the measurement of pressure; the ring-shaped protrusions staggered away from the center of the device increase the effective area between the capacitive electrode plates without increasing the height of the capacitive cavity, thereby improving the overall sensitivity of the device.

[0082] It can be seen that the pressure strain diaphragm 3 and the ring-shaped protrusion structures on the low-resistance silicon substrate are staggered, which does not negatively affect the height of the cavity under the condition of locally reducing the distance between the capacitive electrode plates. The upper and lower staggered ring-shaped protrusions of the application cooperate with each other to increase the effective area between the capacitive first electrode plate and the second electrode plate, thereby increasing the sensitivity of the device. The process of the application is simple and easy to implement, and the electrode material is not limited to aluminum or gold, but can be some other metal material or alloy material.

[0083] Please refer to Figures 1-3 Refer to Figures 4-7 Based on the same inventive concept, the application further provides a preparation method of a MEMS capacitive pressure sensor 100, comprising steps 101-111, wherein:

[0084] Step 101, providing a conductive substrate 1; in the direction of the plane of the conductive substrate 1, the pressure sensor 100 comprises 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 part of the insulating layer 4 in the cavity area 11 to form a plurality of insulatively arranged annular first grooves;

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

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

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

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

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

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

[0093] Step 110, etching a part of the pressure-strained diaphragm 3 in the cavity area 11 in a direction from the pressure-strained diaphragm 3 to the conductive substrate 1 to form an etching hole 32 through the pressure-strained diaphragm 3;

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

[0095] Further, the preparation method of the MEMS capacitive pressure sensor 100 further comprises steps 112 and 113 performed after step 111, wherein:

[0096] Step 112, etching a part of the pressure-strained diaphragm 3 and the insulating layer 4 in the edge area 10 in a direction from the pressure-strained diaphragm 3 to the conductive substrate 1 to form a through hole 49 through the pressure-strained diaphragm 3 and the insulating layer 4;

[0097] Step 113, preparing a first metal pad 51 on one side surface of the pressure-strained diaphragm 3 away from the conductive substrate 1 and a second metal pad 52 on one side surface of the insulating layer 4 away from the conductive substrate 1 where the through hole is located; 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, a step of filling the part of the through hole 2 corresponding to the insulating layer 4 in the through hole 49 with a conductive material can also be included.

[0099] Based on this, a specific embodiment of the preparation method (process flow) of the MEMS capacitive pressure sensor 100 can be provided, including steps 201-204, wherein:

[0100] Step 201, first prepare a low-resistance silicon wafer (conductive substrate 1), vapor deposit a layer of dielectric insulating layer 4 such as SiO2 (silicon dioxide), the insulating layer 4 as a sacrificial layer, then etch the insulating layer 4, and then grow a ring-shaped protrusion (first electrode 12) on the low-resistance silicon substrate, and then etch the insulating layer 4 to form a cavity structure, as shown in FIG. 2, this step completes the required process processing of the substrate, and completes the preparation of the first plate of the capacitor. Figure 4

[0101] Step 202, further, continue to deposit a dielectric insulating layer 4 on the substrate, and after the insulating layer 4 reaches a certain thickness, perform a photoetching to open a ring-shaped groove, and then deposit a layer of low-resistance silicon material to realize the preparation of the protrusion structure (second electrode 31) on the pressure strain diaphragm 3, as shown in FIG. 3, this step completes the required process processing of the pressure strain diaphragm 3, and completes the preparation of the second plate of the capacitor. Figure 5

[0102] Step 203, further, etch the pressure strain diaphragm 3 prepared in step 202 to open an etching hole 32 on the diaphragm, and then etch the sacrificial layer to release the capacitor cavity. After the cavity is released, it is dried, and then the etching hole 32 is filled by a deposition process, as shown in FIG. 4, this step completes the release of the lower cavity of the pressure strain diaphragm. Figure 6

[0103] Step 204, further, as shown in FIG. 5, etch one side of the above-mentioned pressure strain diaphragm 3, open a window on the top layer of material, and then etch the dielectric insulating material (to form a through hole 49), after the etching is completed, deposit a layer of conductive material into the etching channel (through hole 2) to lead out the electrode, and finally form a pad 5 by metal sputtering and removing the excess metal layer. This step completes the required process processing of the electrode of the capacitor plate, and completes the preparation of the electrode. Figure 7

[0104] ​​​​The structure of the application, the substrate annular protrusion and the pressure strain diaphragm 3 staggered annular protrusion, that is, the first electrode 12 and the second electrode 31, increases the effective area between the two capacitor plates, and its projection in the plane of the conductive substrate 1 does not overlap, and the projection gap is greater than 0, and the annular protrusion structure thickness is about half of the capacitor gap (sealing cavity height) and other factors, so that the pressure strain diaphragm 3 is close to the substrate (conductive substrate 1) without collision, that is, the first electrode 12 and the second electrode 31 do not collide, so that the sensitivity of the MEMS capacitive pressure sensor 100 is increased without the need to additionally increase the height of the capacitor gap.

[0105] The working process of the MEMS capacitive pressure sensor 100 of the application is: when the pressure strain diaphragm 3 is subjected to pressure, the diaphragm deforms and approaches the substrate, and the decrease of the gap leads to the increase of the capacitance between the two plates. The change signal of the capacitance can be led out by the pad, and the change of the capacitance is detected by a small capacitance detection circuit, and the pressure data can be obtained after processing.

[0106] The application utilizes the capacitance effect, combines the miniaturization characteristics of the micro-electro-mechanical system (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, low power consumption, and strong portability.

[0107] The technical features of the above-described embodiments can be combined arbitrarily. To make the description simple, all possible combinations of the technical features in the above-described embodiments are not described, but as long as the combinations of the technical features do not exist contradictory, they should be considered as the scope of the present application.

[0108] The above-described embodiments only express several implementation manners of the application, and the description is more specific and detailed, but it should not be understood as a limitation on the patent scope of the application. It should be pointed out that for ordinary skilled in the art, without departing from the concept of the application, a number of modifications and improvements can be made, which are all within the protection scope of the application. Therefore, the patent protection scope of the application should be subject to the appended claims.

Claims

1. A MEMS capacitive pressure sensor, characterized by, comprising: a conductive substrate; in a direction along a plane in which the conductive substrate lies, the pressure sensor comprises a cavity region and a peripheral region surrounding the cavity region; a first electrode layer formed on a side surface of the conductive substrate and located in the cavity region; the first electrode layer comprises a plurality of annular first electrodes arranged in isolation; a pressure strain diaphragm located on a side of the first electrode layer away from the conductive substrate; a second electrode layer formed on a side of the pressure strain diaphragm facing the first electrode layer and located in the cavity region; the second electrode layer comprises a plurality of annular second electrodes arranged in isolation; an insulating layer formed between the conductive substrate and the pressure strain diaphragm and located in the peripheral region; in a direction from a center point in the plane in which the conductive substrate lies to the peripheral region, the first electrodes and the second electrodes are arranged alternately and in isolation; projections of the first electrodes and the second electrodes on the plane in which the conductive substrate lies do not overlap and the projection gap is greater than 0.

2. The MEMS capacitive pressure sensor according to claim 1, wherein: the cavity region comprises a first cavity region and a second cavity region surrounding the first cavity region; the first electrodes and the second electrodes are both located in the second cavity region.

3. The MEMS capacitive pressure sensor according to claim 1 or 2, wherein: further comprising a first metal pad and a second metal pad located in the peripheral 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, wherein: in a direction from the cavity region to the peripheral region, the first metal pad and the second metal pad are arranged on opposite sides of the cavity region.

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

6. The MEMS capacitive pressure sensor according to claim 5, wherein: 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, wherein: the material of preparation of at least one of the conductive substrate and the pressure strain diaphragm comprises low-resistance silicon.

8. The MEMS capacitive pressure sensor according to claim 1 or 2, wherein: the material of preparation of at least one of the first electrodes and the second electrodes comprises at least one of gold and aluminum.

9. A method of manufacturing a MEMS capacitive pressure sensor for manufacturing a MEMS capacitive pressure sensor according to any one of claims 1 to 8, characterized in that, comprising: providing a conductive substrate; in a direction along a plane in which the conductive substrate lies, the pressure sensor comprises a cavity region and a peripheral region surrounding the cavity region; depositing an insulating layer on a side surface of the conductive substrate; etching a part of the insulating layer of the cavity region to form a plurality of insulatively arranged annular first grooves; preparing a first electrode in the first grooves to form a first electrode layer; etching another part of the insulating layer of the cavity region; depositing an insulating layer on a side surface of the conductive substrate facing the first electrode layer; etching a part of the insulating layer of the cavity region to form a plurality of insulatively arranged annular second grooves; the first grooves and the second grooves are alternately and spacedly arranged in a direction from a center point in a plane in which the conductive substrate lies to the edge region; preparing a second electrode in the second grooves to form a second electrode layer; preparing a pressure strain diaphragm on a side surface of the second electrode layer away from the first electrode layer; etching a part of the pressure strain diaphragm of the cavity region in a direction from the pressure strain diaphragm to the conductive substrate to form an etching hole through the pressure strain diaphragm; etching the insulating layer of the cavity region based on the etching hole and filling the etching hole.

10. The method of claim 9, wherein the MEMS capacitive pressure sensor is prepared by, Further comprising: etching a part of the pressure strain diaphragm of the edge region and the insulating layer in a direction from the pressure strain diaphragm to the conductive substrate to form a through hole through the pressure strain diaphragm and the insulating layer; preparing a first metal pad on a side surface of the pressure strain diaphragm away from the conductive substrate and a second metal pad on a side surface of the insulating layer away from the conductive substrate at the through hole; the second metal pad is electrically connected with the conductive substrate through the through hole of the insulating layer.

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