MEMS piezoresistive differential pressure sensor

Abstract

The invention provides an MEMS piezoresistive differential pressure sensor. The MEMS piezoresistive differential pressure sensor comprises a silicon substrate, first glass, second glass, a first fishbone unit, a second fishbone unit and a piezoresistor, the silicon substrate is provided with an anchoring area and a sensitive area; the first glass is fixed in the anchoring area on the first side of the silicon substrate; the second glass is fixed in the anchoring area on the second side of the silicon substrate; the four first fishbone units are arranged on four side walls in the first regular octagonal groove at intervals; the four second fishbone units are arranged on the four side walls in the second regular octagonal groove at intervals; each of the first fishbone unit and the second fishbone unit comprises a plurality of groups of fishbone subunits which are connected in sequence; each fishbone subunit comprises a pressure-sensitive area, a connecting area and a supporting area. The MEMS piezoresistive differential pressure sensor has the technical effects that the sensitivity and the precision of the MEMS piezoresistive differential pressure sensor are improved, and the reliability and the wide range of the MEMS piezoresistive differential pressure sensor under the high-sensitivity design are considered.

Description

Technical Field

[0001] The invention belongs to the technical field of differential pressure sensors, and in particular relates to a MEMS piezoresistive differential pressure sensor. Background Art

[0002] MEMS (Micro-Electro-Mechanical System) piezoresistive differential pressure sensor uses the piezoresistive effect of semiconductor materials to form a Wheatstone bridge through interconnected piezoresistors to convert ambient pressure into electrical signals to measure pressure. Compared with capacitive differential pressure sensors and piezoelectric differential pressure sensors, MEMS piezoresistive differential pressure sensors have good linearity and reliability, so they are widely used in aerospace, industrial control, medical electronics and other fields.

[0003] The sensitive film of the common MEMS piezoresistive differential pressure sensor is mainly square, and the piezoresistors are distributed on the surface of the film. High sensitivity is usually achieved by increasing the area of ​​the sensitive film and reducing the thickness of the sensitive film, but this kind of design idea will reduce the available range of the sensor on the one hand, and reduce the life and reliability of the sensor on the other hand, and the improved sensitivity is limited. In addition, due to problems such as processing technology, packaging, uneven temperature, and the introduction of impurities during use, the stress distribution on the sensitive film is not ideal, which leads to poor actual detection accuracy.

[0004] In addition, due to the influence of temperature, the MEMS piezoresistive differential pressure sensor will have additional zero-point drift, resulting in a decrease in measurement accuracy. Usually, additional stress will be generated during the packaging process of the MEMS piezoresistive differential pressure chip, causing the sensor's zero-point drift and affecting the batch calibration of the product. Summary of the invention

[0005] The present invention aims to solve at least one of the technical problems existing in the prior art and provide a new technical solution for a MEMS piezoresistive differential pressure sensor.

[0006] According to one aspect of the present invention, there is provided a MEMS piezoresistive differential pressure sensor, comprising:

[0007] A silicon substrate, wherein the silicon substrate has an anchoring area and a sensitive area, and the anchoring area is arranged around the outside of the sensitive area; the sensitive area on the first side of the silicon substrate is provided with a first regular octagonal groove, and the sensitive area on the second side of the silicon substrate is provided with a second regular octagonal groove corresponding to the first regular octagonal groove;

[0008] A first glass and a second glass, wherein the first glass is fixed to the anchoring area on the first side of the silicon substrate and forms a first cavity with the sensitive area on the first side of the silicon substrate, and a first through hole is provided at a position of the first glass corresponding to the center of the first regular octagonal groove; the second glass is fixed to the anchoring area on the second side of the silicon substrate and forms a second cavity with the sensitive area on the second side of the silicon substrate, and a second through hole is provided at a position of the second glass corresponding to the center of the second regular octagonal groove;

[0009] A first fishbone unit and a second fishbone unit, four first fishbone units are arranged at intervals on four side walls in the first regular octagonal groove, and respectively extend from the groove bottom of the first regular octagonal groove to the center of the first regular octagonal groove; four second fishbone units are arranged at intervals on four side walls in the second regular octagonal groove, and respectively extend from the groove bottom of the second regular octagonal groove to the center of the second regular octagonal groove; and the first fishbone units and the second fishbone units are staggered;

[0010] A varistor, the first fishbone unit and the second fishbone unit each include a plurality of groups of fishbone sub-units connected in sequence; each group of fishbone sub-units includes a pressure-sensitive area, a connection area and a support area, and one side of the connection area is connected to the pressure-sensitive area, and the other side is connected to the support area; adjacent fishbone sub-units are connected to the pressure-sensitive area of ​​another fishbone sub-unit through the support area of ​​one fishbone sub-unit, and the fishbone sub-unit at the end is connected to the side wall of the first regular octagonal groove or the side wall of the second regular octagonal groove through the pressure-sensitive area; wherein the pressure-sensitive area is provided with a varistor.

[0011] Optionally, adjacent side walls of the first regular octagonal groove and the second regular octagonal groove are transitioned through rounded corners.

[0012] Optionally, the projection of the pressure-sensitive area on the bottom of the first regular octagonal groove or the bottom of the second regular octagonal groove is a rectangle.

[0013] Optionally, the silicon substrate is made of single crystal silicon with a thickness of 200-1000 μm.

[0014] Optionally, the projection of the connection area on the bottom of the first regular octagonal groove or the bottom of the second regular octagonal groove is a rectangle or a plurality of rectangles distributed at intervals.

[0015] Optionally, the length of the connecting area is smaller than the length of the pressure-sensitive area.

[0016] Optionally, the projection of the support area on the groove bottom of the first regular octagonal groove or the groove bottom of the second regular octagonal groove is an isosceles trapezoid, and the upper base and the lower base of the isosceles trapezoid are respectively parallel to a side wall of the first regular octagonal groove or a side wall of the second regular octagonal groove; the included angle between the waist side and the lower base of the isosceles trapezoid is half of the inner angle of the first regular octagonal groove or the inner angle of the second regular octagonal groove;

[0017] The lower bases of the first fishbone unit or the second fishbone unit gradually decrease along a direction from close to the anchoring area to away from the anchoring area.

[0018] Optionally, the thickness of the first fishbone unit and the second fishbone unit are both 10-100 μm.

[0019] Optionally, both the first through hole and the second through hole are circular holes.

[0020] A technical effect of the present invention is:

[0021] In the embodiment of the present application, the MEMS piezoresistive differential pressure sensor utilizes a designed octagonal sensitive film, combined with four first fishbone units and four second fishbone units to form a wave-like layout design, thereby achieving stress concentration in the pressure-sensitive area; in addition, through the characteristics of the fishbone multi-appendage skeleton, multiple groups of Wheatstone bridge combination amplification are designed, and the Wheatstone bridges on both sides of the sensitive area are combined for secondary differential amplification, thereby improving the sensitivity of the MEMS piezoresistive differential pressure sensor.

[0022] Moreover, the MEMS piezoresistive differential pressure sensor adopts a design of four first fishbone units and four second fishbone units, and its appendage bones are evenly and widely distributed, which realizes the role of reinforcing ribs, greatly improves the strength of the sensitive area, and takes into account the reliability and large range of the MEMS piezoresistive differential pressure sensor under high sensitivity design.

[0023] Furthermore, the MEMS piezoresistive differential pressure sensor adopts a design of four first fishbone units and four second fishbone units, and its appendage bones are evenly and widely distributed, so more and more accurate stress data can be collected. This can weaken the influence of non-ideal film stress distribution in sensitive areas caused by processing technology, packaging, uneven temperature, impurities during use, etc., thereby improving the accuracy of actual detection.

[0024] In addition, the MEMS piezoresistive differential pressure sensor forms two Wheatstone bridge outputs above and below the pressure-sensitive area, which improves the sensitivity of the MEMS piezoresistive differential pressure sensor, and through the differential amplifier circuit, it achieves self-compensation for the additional zero-point drift caused by temperature stress and packaging stress, which is beneficial to improving the accuracy of subsequent batch calibration and conditioning of the sensor. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a schematic diagram of the overall structure of a MEMS piezoresistive differential pressure sensor according to an embodiment of the present invention;

[0026] Figure 2 A top view of a MEMS piezoresistive differential pressure sensor according to an embodiment of the present invention;

[0027] Figure 3 A bottom view of a MEMS piezoresistive differential pressure sensor according to an embodiment of the present invention;

[0028] Figure 4 A schematic structural diagram of a fishbone subunit of a first fishbone unit of a MEMS piezoresistive differential pressure sensor according to an embodiment of the present invention;

[0029] Figure 5 A schematic structural diagram of a fishbone subunit of a second fishbone unit of a MEMS piezoresistive differential pressure sensor according to an embodiment of the present invention;

[0030] Figure 6 The figure is a cross-sectional schematic diagram of a MEMS piezoresistive differential pressure sensor according to an embodiment of the present invention.

[0031] In the figure: 1, silicon substrate; 11, anchoring area; 12, sensitive area; 21, first fishbone unit; 22, second fishbone unit; 201, pressure-sensitive area; 202, connection area; 203, support area; 31, first glass; 32, second glass; 41, first through hole; 42, second through hole. DETAILED DESCRIPTION

[0032] Various exemplary embodiments of the present application will now be described in detail with reference to the accompanying drawings. It should be noted that unless otherwise specifically stated, the relative arrangement of components and steps, numerical expressions and numerical values ​​set forth in these embodiments do not limit the scope of the present application.

[0033] The embodiments of the present application will be described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present application, and should not be construed as limitations on the present application. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without making creative work are within the scope of protection of the present application.

[0034] The term "first" or "second" in the specification and claims of this application may include one or more of the features explicitly or implicitly. In the description of this application, unless otherwise specified, "plurality" means two or more. In addition, "and / or" in the specification and claims means at least one of the connected objects, and the character " / " generally means that the objects connected before and after are in an "or" relationship.

[0035] In the description of the present application, it should be understood that 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" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0036] In the description of this application, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0037] According to the first aspect of the present invention, a MEMS piezoresistive differential pressure sensor is provided, which can solve the problem that the sensitivity, range and reliability of the existing MEMS piezoresistive differential pressure sensor cannot be taken into account at the same time, and reduces the zero drift of the MEMS piezoresistive differential pressure sensor caused by temperature and packaging stress, weakens the accuracy degradation problem caused by non-ideal stress distribution of the sensitive film during processing technology, temperature unevenness, packaging, use and other processes, and improves the accuracy and reliability of the MEMS piezoresistive differential pressure sensor.

[0038] See also Figure 1 and Figure 6 , define the first direction as the X-axis direction, the second direction as the Y-axis direction, and the third direction as the Z-axis direction, and the X-axis direction, the Y-axis direction, and the Z-axis direction are perpendicular to each other.

[0039] Specifically, see Figures 1 to 6 , the MEMS piezoresistive differential pressure sensor comprises:

[0040] A silicon substrate 1, wherein the silicon substrate 1 has an anchoring region 11 and a sensitive region 12, and the anchoring region 11 is arranged around the outside of the sensitive region 12; the sensitive region 12 on the first side of the silicon substrate 1 is provided with a first regular octagonal groove, and the sensitive region 12 on the second side of the silicon substrate 1 is provided with a second regular octagonal groove corresponding to the first regular octagonal groove; it should be noted that the groove bottom of the first regular octagonal groove or the second regular octagonal groove is the bottom surface, and the side wall is the side surface;

[0041] A first glass 31 and a second glass 32, wherein the first glass 31 is fixed to the anchoring area 11 on the first side of the silicon substrate 1, and forms a first cavity with the sensitive area 12 on the first side of the silicon substrate 1, and a first through hole 41 is provided at a position of the first glass 31 corresponding to the center of the first regular octagonal groove; the second glass 32 is fixed to the anchoring area 11 on the second side of the silicon substrate 1, and forms a second cavity with the sensitive area 12 on the second side of the silicon substrate 1, and a second through hole 42 is provided at a position of the second glass 32 corresponding to the center of the second regular octagonal groove; wherein the first through hole 41 is connected to the first cavity; and the second through hole 42 is connected to the second cavity;

[0042] The first fishbone unit 21 and the second fishbone unit 22, the four first fishbone units 21 are arranged at intervals on the four side walls in the first regular octagonal groove, and respectively extend on the groove bottom of the first regular octagonal groove toward the center of the first regular octagonal groove, that is, the four first fishbone units 21 are fixedly connected to the groove bottom of the first regular octagonal groove on one side; the four second fishbone units 22 are arranged at intervals on the four side walls in the second regular octagonal groove, and respectively extend on the groove bottom of the second regular octagonal groove. The bottom of the groove extends toward the center of the second regular octagonal groove, that is, one side of the four second fishbone units 22 facing the bottom of the second regular octagonal groove is fixedly connected to the bottom of the second regular octagonal groove; and the first fishbone units 21 and the second fishbone units 22 are staggered; wherein each first fishbone unit 21 corresponds to a fishbone area on the first side of the silicon substrate 1, and each second fishbone unit 22 corresponds to a fishbone area on the second side of the silicon substrate 1, and the four first fishbone units 21 and the four second fishbone units 22 constitute eight fishbone areas in total;

[0043] Varistor, the first fishbone unit 21 and the second fishbone unit 22 each include a plurality of groups of fishbone sub-units connected in sequence; each group of fishbone sub-units includes a pressure-sensitive area 201, a connection area 202 and a support area 203, and one side of the connection area 202 is connected to the pressure-sensitive area 201, and the other side is connected to the support area 203; adjacent fishbone sub-units are connected to the pressure-sensitive area 201 of another fishbone sub-unit through the support area 203 of one fishbone sub-unit, and the fishbone sub-unit at the end is connected to the side wall of the first regular octagonal groove or the side wall of the second regular octagonal groove through the pressure-sensitive area; wherein the pressure-sensitive area 201 is provided with a varistor. The main purpose of the support area 203 is to reduce the stress in the non-pressure-sensitive area and improve the actual strength of the sensitive area 12.

[0044] It should be noted that the working principle of the MEMS piezoresistive differential pressure sensor of the present invention is as follows:

[0045] On the one hand, in an actual application environment, different pressure media contact the silicon substrate 1 through the first through hole 41 and the second through hole 42 respectively, causing deformation of the sensitive area 12 and generating corresponding stress, and generating tensile stress or tensile stress in eight fishbone areas, namely, four first fishbone units 21 and four second fishbone units 22, causing corresponding sensitive resistors on the pressure-sensitive area 201 to generate corresponding resistance changes, and output electrical signals to represent the current pressure difference or pressure.

[0046] Secondly, in actual use, since the range of the MEMS differential pressure sensor is usually small, a relatively large sensitivity is required. In this embodiment, there are multiple groups of the pressure-sensitive areas 201 on the fishbone area on each side of the sensitive area 12, which can form a corresponding number of Wheatstone bridges, greatly improving the sensitivity of the MEMS piezoresistive differential pressure sensor. At the same time, the Wheatstone bridges on the first and second sides of the sensitive area 12 form a second-stage differential amplifier circuit, which doubles the sensitivity of the MEMS piezoresistive differential pressure sensor. In addition, the fishbone area structure design composed of the pressure-sensitive area 201, the connection area 202, and the support area 203 in this embodiment achieves better film stress concentration and further improves the sensitivity of the MEMS differential pressure sensor.

[0047] Thirdly, the special structural design of the eight fishbone areas uses the pressure-sensitive area 201 and the connection area 202 as the appendages of the fishbone, which plays a role similar to that of a reinforcing rib. While ensuring the sensitivity of the MEMS differential pressure sensor, the strength of the sensitive area 12 is taken into account, thereby improving the reliability and actual range of the MEMS differential pressure sensor. At the same time, the pressure-sensitive area 201 is more widely and evenly distributed, which improves the sensitivity of the MEMS differential pressure sensor on the one hand, and collects more accurate pressure values ​​on the other hand, weakening the effects of processing technology, temperature, packaging, use, etc. on the sensitive area 12, thereby reducing measurement errors.

[0048] Fourthly, in this embodiment, the eight fishbone areas are evenly and staggeredly distributed on the opposite sides (i.e., the first side and the second side) of the sensitive area 12, and each corresponds to one side of the regular octagon. This wavy distribution can reduce the stress concentration at the edge of the fishbone, increase the stress at the pressure-sensitive area 201 to improve the sensitivity, and reduce the stress at the weak point to improve the reliability of the device. At the same time, this design can obtain a more accurate stress distribution in the sensitive area 12. Through the differential output of the Wheatstone bridge on the first side and the second side of the sensitive area 12, the additional zero drift caused by temperature and stress of the MEMS piezoresistive differential pressure sensor can be reduced, thereby improving the accuracy of the sensor. And through the differential output of the Wheatstone bridge on the first side and the second side of the sensitive area 12, the output drift and nonlinearity caused by thermal stress are reduced, and self-compensation of temperature drift is achieved.

[0049] In the embodiment of the present application, the MEMS piezoresistive differential pressure sensor utilizes a designed octagonal sensitive film, combined with four first fishbone units 21 and four second fishbone units 22 to form a wave-like layout design, thereby achieving stress concentration in the pressure-sensitive area 201; in addition, through the characteristics of the fishbone multi-appendage skeleton, multiple groups of Wheatstone bridge combination amplification are designed, and the Wheatstone bridges on both sides of the sensitive area 12 are combined for secondary differential amplification, thereby improving the sensitivity of the MEMS piezoresistive differential pressure sensor.

[0050] Moreover, the MEMS piezoresistive differential pressure sensor adopts a design of four first fishbone units 21 and four second fishbone units 22, and its appendages are evenly and widely distributed, which realizes the role of reinforcing ribs, greatly improves the strength of the sensitive area 12, and takes into account the reliability and large range of the MEMS piezoresistive differential pressure sensor under high sensitivity design.

[0051] Furthermore, the MEMS piezoresistive differential pressure sensor adopts a design of four first fishbone units 21 and four second fishbone units 22, and its appendage bones are evenly and widely distributed, so more and more accurate stress data can be collected, which can weaken the non-ideal influence of film stress distribution in the sensitive area 12 caused by processing technology, packaging, uneven temperature, impurities during use, etc., thereby improving the accuracy of actual detection.

[0052] In addition, the MEMS piezoresistive differential pressure sensor forms two Wheatstone bridge outputs above and below the pressure-sensitive area 201, which improves the sensitivity of the MEMS piezoresistive differential pressure sensor, and through the differential amplifier circuit, realizes self-compensation for the additional zero-point drift caused by temperature stress and packaging stress, which is beneficial to improving the accuracy of subsequent batch calibration and conditioning of the sensor.

[0053] In a specific embodiment, the silicon substrate 1 is made of single crystal silicon with a thickness of 200-1000 μm. The thickness of the anchoring region 11 is the same as that of the silicon substrate 1 , and the thickness of the sensitive region 12 is 10-100 μm.

[0054] Exemplarily, the projection shape of the sensitive area 12 along the third direction is a regular octagon.

[0055] In this embodiment, eight fishbone areas are staggered on one side of the octagon on both sides of the sensitive area 12, the purpose of which is to ensure that the sensitive area 12 is projected on the cylindrical side section parallel to the third direction as an up and down wavy shape, and a smaller thickness design can be achieved while ensuring the strength of the sensitive area 12, thereby improving the sensitivity of the MEMS piezoresistive differential pressure sensor. Moreover, the eight fishbone areas are staggered on one side of the octagon of the sensitive area 12, and are evenly distributed on both sides of the sensitive area 12, forming a wave-like up and down distribution structure. Compared with arranging fishbone areas on both sides of the same position of the sensitive area 12, the advantage is that the thickness difference between the fishbone area and the sensitive area 12 is smaller and smoother, and the stress is not easily concentrated at the boundary between the fishbone area and the sensitive area 12, so as to improve the sensitivity of the MEMS piezoresistive differential pressure sensor and improve the reliability of the device.

[0056] In addition, the eight fishbone areas are staggered on one side of the octagon of the sensitive area 12, and are evenly distributed on both sides of the sensitive area 12, forming a wave-like upper and lower distribution structure, the purpose of which is to more evenly collect the stress at different positions on the sensitive area 12 to reduce the additional impact of uneven loads, thereby better realizing the zero drift compensation of the MEMS piezoresistive differential pressure sensor.

[0057] Optionally, adjacent side walls of the first regular octagonal groove and the second regular octagonal groove are transitioned through rounded corners.

[0058] In the above embodiment, the sensitive area 12 adopts an optimized rounded octagonal groove structure, which has a better stress concentration effect compared to the traditional rectangular film, and can reduce the stress concentration in the area where the non-sensitive film is located, increase the sensitivity of the MEMS piezoresistive differential pressure sensor, and improve its reliability.

[0059] For example, the first glass 31 is located above the silicon substrate 1 along the third direction, and the second glass 32 is located below the silicon substrate 1 along the third direction. The first glass 31 and the second glass 32 are both made of 7740 glass, and the thickness is 500 μm. In other embodiments, other glass types and thicknesses can be used according to specific needs.

[0060] Furthermore, the first glass 31 and the second glass 32 are used to protect the silicon substrate 1 to ensure the normal operation of the MEMS piezoresistive differential pressure sensor, and to reduce the drift error caused by direct contact between impurities and the sensitive area 12 during packaging or use. At the same time, the first glass 31 and the second glass 32 are symmetrically distributed, and the zero bias of the MEMS piezoresistive differential pressure sensor caused by thermal stress and packaging stress can be greatly reduced through differential output.

[0061] Exemplarily, the first fishbone unit 21 and the second fishbone unit 22 each have six groups of fishbone sub-units. In other embodiments, other distribution groups may also be designed according to actual conditions.

[0062] Optionally, the projection of the pressure-sensitive area 201 on the bottom of the first regular octagonal groove or the bottom of the second regular octagonal groove is a rectangle. The projection on the bottom of the first regular octagonal groove or the bottom of the second regular octagonal groove is also a projection along the third direction. For example, the projection of the pressure-sensitive area 201 along the third direction is a rectangle of 200 μm*20 μm.

[0063] In one embodiment, the purpose of the pressure-sensitive area 201 is to be used for subsequent processing of the varistor. The specific size of the pressure-sensitive area 201 is consistent with the actual size of the varistor. Through the self-limiting structure, the accuracy of the length and width of the varistor actually processed is ensured, the resistance value and piezoresistance coefficient processing accuracy of the processed varistor are improved, and the actual accuracy of the MEMS piezoresistive differential pressure sensor is guaranteed.

[0064] Optionally, the projection of the connection area 202 on the bottom of the first regular octagonal groove or the bottom of the second regular octagonal groove is a rectangle or a plurality of rectangles distributed at intervals.

[0065] In the above embodiment, the connection area 202 is a rectangular block, and the connection strength between the connection area 202 and the pressure-sensitive area 201 can also be increased by increasing the number of rectangular blocks. For example, a plurality of connection areas 202 are distributed in an array.

[0066] Optionally, the length of the connecting area 202 is smaller than the length of the varistor area 201. This helps to more accurately position the varistor area 201 when preparing the varistor, so as to ensure the dimensional accuracy of the varistor.

[0067] Optionally, the projection of the support area 203 on the bottom of the first regular octagonal groove or the bottom of the second regular octagonal groove is an isosceles trapezoid, and the upper base and the lower base of the isosceles trapezoid are respectively parallel to a side wall of the first regular octagonal groove or a side wall of the second regular octagonal groove; the angle between the waist side and the lower base of the isosceles trapezoid is half of the inner angle of the first regular octagonal groove or the inner angle of the second regular octagonal groove;

[0068] The lower bases of the first fishbone unit 21 or the second fishbone unit 22 gradually decrease along a direction from close to the anchoring area 11 to away from the anchoring area 11 .

[0069] In the above embodiment, the multiple support areas 203 of the same fishbone sub-unit are similar but not identical, and the support area 203 closer to the center of the sensitive area 12 is smaller, thereby ensuring that each fishbone area (that is, the first fishbone unit 21 and the second fishbone unit 22) is only located in one eighth of the sensitive area 12, thereby better ensuring the accuracy and sensitivity of the differential pressure sensor.

[0070] Optionally, the thickness of the first fishbone unit 21 and the second fishbone unit 22 are both 10-100 μm, which helps to improve the sensitivity of the sensitive area 12 .

[0071] Optionally, the first through hole 41 and the second through hole 42 are both circular holes, which is convenient for reducing concentrated stress during glass processing and improving the strength of the first glass 31 and the second glass 32 .

[0072] In other embodiments, one of the first through hole 41 and the second through hole 42 may not be processed to serve as an absolute pressure sensor.

[0073] In this embodiment, the first through hole 41 is located at the center of the first glass 31 and exposes the sensitive area 12. The second through hole 42 is located at the center of the second glass 32 and exposes the sensitive area 12.

[0074] Exemplarily, the diameters of the first through hole 41 and the second through hole 42 are both 100-2000 μm. In other embodiments, other through hole sizes and shapes may be used according to specific needs.

[0075] In one embodiment, the thickness of the first fishbone unit 21 and the second fishbone unit 22 are respectively 10-100 μm.

[0076] For example, there is a height difference between the eight fishbone areas and the sensitive area 12, the purpose of which is to increase the local stress to improve the sensitivity of the MEMS piezoresistive differential pressure sensor. In addition, the subsequent doping, film deposition, etching and other processes are completed based on the thicker eight fishbone areas. Compared with processing directly on the sensitive area 12, the subsequent processing technology avoids damage to the sensitive film, thereby ensuring the processing accuracy.

[0077] In the embodiment of the present application, each fishbone subunit is distributed in groups in sequence by the pressure-sensitive area 201, the connection area 202, and the support area 203, and its overall projection along the third direction is similar to a fishbone, and the pressure-sensitive area 201 and the connection area 202 are the appendage bones of the fishbone. The more groups the pressure-sensitive area 201, the connection area 202, and the support area 203 are arrayed in, the more appendage bones of the fishbone, the more Wheatstone bridges are formed, the higher the actual output of the MEMS piezoresistive differential pressure sensor, and the higher the sensitivity. And the more appendage bones of the fishbone, the stronger the actual fish body, that is, the higher the strength of the sensitive area 12, which ensures the reliability of the MEMS piezoresistive differential pressure sensor and improves its actual range. The incompatibility of indicators such as sensitivity, strength, and range of traditional piezoresistive pressure sensors is solved. Moreover, the pressure-sensitive area 201 is distributed more widely than the traditional varistor, and a more uniform and accurate stress distribution at each point in the sensitive area 12 can be obtained, which not only reduces the precision error caused by process errors such as uneven thickness of the sensitive area 12, and eliminates the precision error caused by local impurities in the sensitive area 12 during packaging or use, but also helps to reduce the precision error caused by uneven local stress due to uneven temperature distribution in the sensitive area 12. Compared with the traditional varistor distribution, it has more accurate pressure detection.

[0078] It is to be understood that the above embodiments are merely exemplary embodiments used to illustrate the principles of the present invention, but the present invention is not limited thereto. For those of ordinary skill in the art, various modifications and improvements can be made without departing from the spirit and essence of the present invention, and these modifications and improvements are also considered to be within the scope of protection of the present invention.

Claims

1. A MEMS piezoresistive differential pressure sensor, characterized in that: include: A silicon substrate, wherein the silicon substrate has an anchoring area and a sensitive area, and the anchoring area is arranged around the outside of the sensitive area; the sensitive area on the first side of the silicon substrate is provided with a first regular octagonal groove, and the sensitive area on the second side of the silicon substrate is provided with a second regular octagonal groove corresponding to the first regular octagonal groove; A first glass and a second glass, wherein the first glass is fixed to the anchoring area on the first side of the silicon substrate and forms a first cavity with the sensitive area on the first side of the silicon substrate, and a first through hole is provided at a position of the first glass corresponding to the center of the first regular octagonal groove; the second glass is fixed to the anchoring area on the second side of the silicon substrate and forms a second cavity with the sensitive area on the second side of the silicon substrate, and a second through hole is provided at a position of the second glass corresponding to the center of the second regular octagonal groove; A first fishbone unit and a second fishbone unit, four first fishbone units are arranged at intervals on four side walls in the first regular octagonal groove; four second fishbone units are arranged at intervals on four side walls in the second regular octagonal groove; and the first fishbone units and the second fishbone units are staggered; A varistor, the first fishbone unit and the second fishbone unit each include a plurality of groups of fishbone sub-units connected in sequence; each group of fishbone sub-units includes a pressure-sensitive area, a connection area and a support area, and one side of the connection area is connected to the pressure-sensitive area, and the other side is connected to the support area; adjacent fishbone sub-units are connected to the pressure-sensitive area of ​​another fishbone sub-unit through the support area of ​​one fishbone sub-unit, and the fishbone sub-unit at the end is connected to the side wall of the first regular octagonal groove or the side wall of the second regular octagonal groove through the pressure-sensitive area; wherein the pressure-sensitive area is provided with a varistor.

2. The MEMS piezoresistive differential pressure sensor according to claim 1, characterized in that: Adjacent side walls of the first regular octagonal groove and the second regular octagonal groove are transitioned by rounded corners.

3. The MEMS piezoresistive differential pressure sensor according to claim 1, characterized in that: The projection of the pressure-sensitive area on the bottom of the first regular octagonal groove or the bottom of the second regular octagonal groove is a rectangle.

4. The MEMS piezoresistive differential pressure sensor according to claim 1, characterized in that: The silicon substrate is made of single crystal silicon with a thickness of 200-1000 μm.

5. The MEMS piezoresistive differential pressure sensor according to claim 1, characterized in that: The projection of the connection area on the groove bottom of the first regular octagonal groove or the groove bottom of the second regular octagonal groove is a rectangle or a plurality of rectangles distributed at intervals.

6. The MEMS piezoresistive differential pressure sensor according to claim 1, characterized in that: The length of the connecting area is smaller than the length of the pressure sensitive area.

7. The MEMS piezoresistive differential pressure sensor according to claim 1, characterized in that: The projection of the support area on the bottom of the first regular octagonal groove or the bottom of the second regular octagonal groove is an isosceles trapezoid, and the upper base and the lower base of the isosceles trapezoid are respectively parallel to a side wall of the first regular octagonal groove or a side wall of the second regular octagonal groove; the angle between the waist side and the lower base of the isosceles trapezoid is half of the inner angle of the first regular octagonal groove or the inner angle of the second regular octagonal groove; The lower bases of the first fishbone unit or the second fishbone unit gradually decrease along a direction from close to the anchoring area to away from the anchoring area.

8. The MEMS piezoresistive differential pressure sensor according to claim 1, characterized in that: The thickness of the first fishbone unit and the second fishbone unit are both 10-100 μm.

9. The MEMS piezoresistive differential pressure sensor according to claim 1, characterized in that: The first through hole and the second through hole are both circular holes.

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