Pressure sensing module and pressure sensor

Abstract

The invention provides a pressure sensing module and a pressure sensor, and relates to the technical field of micro-electronic machinery, and the pressure sensing module is provided with an isolation groove to further improve the precision of a piezoresistor. The pressure sensing module comprises a first substrate and a second substrate which are oppositely arranged, wherein a cavity is formed between the first substrate and the second substrate; the side, away from the second substrate, of the first substrate is provided with a piezoresistor and an isolation groove, and the isolation groove is arranged around at least part of the piezoresistor.

Description

Technical Field

[0001] The present application relates to the field of micro-electromechanical technology, and in particular to a pressure sensing module and a pressure sensor. Background Art

[0002] Micro-Electro-Mechanical System (MEMS) pressure sensor modules are micro devices with pressure detection capabilities made through MEMS technology. They are mainly divided into three categories: piezoresistive, capacitive, and resonant. They can be used in consumer electronics, industrial production, and other fields. Among them, piezoresistive MEMS pressure sensor modules have the advantages of small size, light weight, simple structure, low cost, and high measurement accuracy, so they have been widely used.

[0003] The varistor in the existing pressure sensing module is formed by injecting ions into the device layer. The varistor injection process has diffusion problems, and the precision of the formed varistor is low. Summary of the invention

[0004] The present invention provides a pressure sensing module and a pressure sensor. The pressure sensing module further improves the accuracy of a varistor by arranging an isolation groove.

[0005] In a first aspect, the present application provides a pressure sensing module. The pressure sensing module comprises: a first substrate and a second substrate arranged opposite to each other, a cavity formed between the first substrate and the second substrate; a piezoresistor and an isolation groove are arranged on a side of the first substrate away from the second substrate, and the isolation groove is arranged around at least part of the piezoresistor.

[0006] Some embodiments of the present application provide a pressure sensing module, which improves the sensitivity of a varistor by means of an isolation groove. By setting an isolation groove around the varistor, the specification of the formed varistor is more complete and the accuracy is higher, which is convenient for subsequent pressure detection. At the same time, the isolation groove can also protect and isolate the varistor.

[0007] In some embodiments, the first substrate includes a first substrate layer, a buried oxide layer, and a device layer stacked in sequence in a direction away from the second substrate; the varistor and the isolation trench are arranged in the device layer, and the notch of the isolation trench is located on the surface of the device layer away from the buried oxide layer.

[0008] In some embodiments, a surface of the varistor facing away from the buried oxide layer is flush with a surface of the device layer facing away from the buried oxide layer.

[0009] In some embodiments, the varistor includes a microelectronic material and doping ions, the device layer includes a microelectronic material, and the microelectronic material included in the varistor is the same as the microelectronic material included in the device layer.

[0010] In some embodiments, there is a distance between the surface of the varistor close to the buried oxide layer and the buried oxide layer, and there is also a distance between the bottom of the isolation trench and the buried oxide layer; wherein the isolation trench is formed by etching on the device layer.

[0011] In some embodiments, the first substrate layer is provided with a through hole penetrating along the thickness direction thereof, and the first substrate layer and the buried oxide layer form a groove, and the groove is used to form the cavity.

[0012] In some embodiments, along the thickness direction of the first substrate, the size of the varistor is less than or equal to the depth of the isolation trench.

[0013] In some embodiments, the isolation groove is extended along the contour of a side of the varistor close to the center of the first substrate.

[0014] In some embodiments, the number of the varistors is four and they are arranged along the circumference of the first substrate; the number of the isolation grooves is four and one isolation groove is arranged around one side of the varistor close to the center of the first substrate.

[0015] In some embodiments, a width of the isolation trench is greater than or equal to 10 μm and less than or equal to 50 μm.

[0016] In some embodiments, a depth of the isolation trench is greater than or equal to 0.4 μm and less than or equal to 1.2 μm.

[0017] In some embodiments, the pressure sensing module further includes: interconnecting wires, the interconnecting wires are electrically connected to the plurality of piezoresistors; the interconnecting wires are arranged around the plurality of piezoresistors and the plurality of isolation grooves.

[0018] In a second aspect, the present application provides a pressure sensor, which includes: a pressure sensing module and an integrated circuit, wherein the integrated circuit is electrically connected to the pressure sensing module.

[0019] The beneficial effects of the pressure sensor are the same as those of the pressure sensing module and will not be elaborated here.

[0020] In a third aspect, the present application provides an electronic device, which includes: the above-mentioned pressure sensor.

[0021] The beneficial effects of the electronic device are the same as those of the pressure sensor and will not be described in detail here. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The drawings described herein are used to provide a further understanding of the embodiments of the present disclosure and constitute a part of the embodiments of the present disclosure. The illustrative embodiments of the present disclosure and their descriptions are used to explain the present disclosure and do not constitute an improper limitation on the present disclosure. In the drawings: Figure 1 A schematic diagram of a pressure sensing module provided for some embodiments of the present disclosure; Figure 2 A side view of a pressure sensing module provided for some embodiments of the present disclosure; Figure 3 A schematic diagram of a front side of a first substrate provided for some embodiments of the present disclosure; Figure 4 A schematic diagram of the back side of a first substrate provided for some embodiments of the present disclosure; Figure 5 A schematic diagram of a pressure sensor provided for some embodiments of the present disclosure; Figure 6 A schematic diagram of another pressure sensor provided for some embodiments of the present disclosure; Figure 7 A schematic diagram of an electronic device provided for some embodiments of the present disclosure.

[0023] Reference numerals 10. First substrate; 20. Second substrate; 11. Varistor; 12. Isolation groove; 13. Device layer; 14. Buried oxide layer; 15. First substrate layer; 16. First metal layer; 17. First connection layer; 18. Metal pad; 19. Interconnection wire; 21. Second substrate layer; 22. Second metal layer; 23. Second connection layer; N. Cavity; 100. Pressure sensing module; 150. Integrated circuit; 200. Pressure sensor; 300. Electronic device; 310. Housing. DETAILED DESCRIPTION

[0024] The following will be combined with the accompanying drawings to clearly and completely describe the technical solutions in some embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments provided by the present application, all other embodiments obtained by ordinary technicians in this field belong to the scope of protection of the present application.

[0025] Unless the context requires otherwise, throughout the specification and claims, the term "including" is to be interpreted as an open, inclusive meaning, that is, "including, but not limited to". In the description of the specification, the terms "one embodiment", "some embodiments", "exemplary embodiments", "examples" or "some examples" and the like are intended to indicate that specific features, structures, materials or characteristics associated with the embodiment or example are included in at least one embodiment or example of the present application. The schematic representation of the above terms does not necessarily refer to the same embodiment or example. In addition, the specific features, structures, materials or characteristics described may be included in any one or more embodiments or examples in any appropriate manner.

[0026] Micro-Electro-Mechanical System (MEMS) pressure sensor modules are micro devices with pressure detection capabilities made through MEMS technology. They are mainly divided into three categories: piezoresistive, capacitive, and resonant. They can be used in consumer electronics, industrial production, and other fields. Among them, piezoresistive MEMS pressure sensor modules have the advantages of small size, light weight, simple structure, low cost, and high measurement accuracy, so they have been widely used.

[0027] The varistor in the existing pressure sensing module is formed by injecting ions into the device layer. The varistor injection process has diffusion problems, and the precision of the formed varistor is low.

[0028] It should be noted that the piezoresistive MEMS pressure sensing module includes a pressure-sensitive film (also called a strain film), a piezoresistor and a circuit structure, and the piezoresistor and the circuit structure are electrically connected. The working principle of the piezoresistive MEMS pressure sensing module can be: by preparing a piezoresistor on the strain film, the strain film deforms under the action of external pressure and generates stress, and the piezoresistor changes its resistance value under the action of stress, and finally the resistance change is converted into a voltage output through an interconnection structure (such as a Wheatstone bridge). Therefore, the magnitude of the external pressure can be reflected by the voltage output value.

[0029] Based on this, some embodiments of the present application provide a pressure sensing module. Figure 1 As shown, the pressure sensing module 100 includes: a first substrate 10 and a second substrate 20 .

[0030] The first substrate 10 and the second substrate 20 are arranged opposite to each other, and a cavity is formed between the first substrate 10 and the second substrate 20; a varistor 11 and an isolation groove 12 are provided on a side of the first substrate 10 away from the second substrate 20, and the isolation groove 12 is arranged around at least a portion of the varistor 11.

[0031] Firstly, the isolation groove 12 is arranged at least partially around the varistor 11, which means: In the first case, the isolation grooves 12 are disposed around a portion of the varistors 11 , while the isolation grooves 12 are not disposed around another portion of the varistors 11 .

[0032] The portion with the isolation groove 12: First, the injection process will cause lateral diffusion, resulting in the actual resistor size not being the designed value. Therefore, by making an isolation groove and removing the lateral diffusion portion, accurate resistor size measurement that meets the designed value can be achieved, thereby improving the consistency of the resistor value and improving the sensor accuracy.

[0033] Moreover, with the isolation groove 12, the varistor 11 is better electrically and physically isolated, reducing the mutual interference with other circuit elements, and improving the accuracy and stability of the measurement. At the same time, only providing the isolation groove 12 for part of the varistor 11 is a cost optimization strategy.

[0034] In the second case, isolation grooves 12 are arranged around all the varistors 11 .

[0035] First, the injection process will cause lateral diffusion, resulting in the actual resistor size not being the designed value. Therefore, by making an isolation groove and removing the lateral diffusion part, accurate resistor size measurement that meets the design value can be achieved, thereby improving the consistency of the resistor value and improving the accuracy of the sensor.

[0036] All varistors 11 are well electrically and physically isolated, which can minimize mutual interference and the influence of the external environment, thereby improving the measurement accuracy and stability of the entire pressure sensing module 100. Since all varistors 11 are provided with isolation slots 12, the cost of this configuration may be higher than the first case. However, in some applications that require extremely high measurement accuracy, this cost increase is more preferable.

[0037] The design of the isolation groove 12 can effectively isolate the varistor 11 from other possible interference sources (such as other electronic components inside the module, electromagnetic interference from the external environment, etc.), thereby reducing the impact of these interferences on the measurement accuracy of the varistor 11. By reducing interference, the isolation groove 12 helps to improve the measurement accuracy of the pressure sensing module 100, allowing the module to more accurately reflect the actual situation of the external pressure.

[0038] Based on the above scheme, some embodiments of the present application provide a pressure sensing module 100, which improves the sensitivity of the varistor 11 through the isolation groove 12. By arranging the isolation groove 12 around the varistor 11, the specifications of the formed varistor 11 are more complete and the accuracy is higher, which is convenient for subsequent pressure detection. At the same time, the isolation groove 12 can also protect and isolate the varistor 11.

[0039] like Figure 1and Figure 2 As shown, the first substrate 10 includes a first substrate layer 15, a buried oxide layer 14 and a device layer 13 which are stacked in sequence in a direction away from the second substrate 20; the varistor 11 and the isolation groove 12 are arranged in the device layer 13, and the notch of the isolation groove 12 is located on the surface of the device layer 13 away from the buried oxide layer 14.

[0040] Among them, the varistor 11 is formed in the device layer 13 by ion implantation. Ion implantation is the process of injecting a specific type of ions (such as boron, phosphorus, arsenic, etc.) into a silicon wafer (in this case, the SOI device layer 13) at high speed. By precisely controlling parameters such as the implantation dose, angle, depth, and process temperature, the conductive properties of the silicon wafer are changed or a specific impurity distribution is formed. By adjusting the type and concentration of the implanted ions, the resistance value of the resistor can be precisely controlled to meet specific circuit requirements.

[0041] The isolation groove 12 is formed around the varistor 11 in the device layer 13 by etching.

[0042] In some embodiments, the pressure sensing module 100 is back-cavity etched to the buried oxide layer to ensure good etching morphology and etching depth consistency.

[0043] like Figure 2 As shown, in some embodiments, the depth L1 of the varistor 11 formed by ion implantation is 0.4 μm-1 μm.

[0044] like Figure 2 As shown, in some embodiments, the depth of the isolation trench 12 is greater than or equal to 0.4 μm and less than or equal to 1.2 μm.

[0045] In some embodiments, along the thickness direction of the first substrate 10 , the size of the varistor 11 is less than or equal to the depth of the isolation trench 12 .

[0046] For example, the depth of the varistor 11 is 1 μm, the depth of the isolation groove 12 is 1 μm, and the depth of the varistor 11 is the same as that of the isolation groove 12. In other words, the depth of the isolation groove 12 can be equal to the depth of the varistor 11, or greater than the depth of the varistor 11, but not too much greater, generally within a range greater than 0.2 μm.

[0047] The consistent depth of the varistor 11 and the isolation groove 12 helps to achieve better performance matching. The main function of the isolation groove 12 is to achieve a more precise size of resistance and to isolate and protect the varistor 11 from interference or damage from the external environment. The varistor 11 and the isolation groove 12 with the same depth can work better together to ensure the stability and reliability of the varistor 11.

[0048] That is to say, the isolation trench depth ranges from the resistor depth (injection junction depth, 0.4μm-1μm) to the resistor depth + 0.2μm. If the depth is too small, high-precision size resistors cannot be formed; if the depth is too large, it will cause stress redistribution problems and affect linearity performance.

[0049] In some embodiments, a surface of the varistor 11 facing away from the buried oxide layer 14 is flush with a surface of the device layer 13 facing away from the buried oxide layer 14 .

[0050] The flush design makes the production process simpler and more uniform, and no additional processing or adjustment is required for the varistor 11. At the same time, when the varistor 11 is flush with the surface of the device layer 13, the space can be used more effectively, making the structure of the entire device more compact.

[0051] In some embodiments, the varistor 11 includes a microelectronic material and doping ions, the device layer 13 includes a microelectronic material, and the microelectronic material included in the varistor 11 is the same as the microelectronic material included in the device layer 13 .

[0052] The varistor 11 includes microelectronic materials and doped ions, which means that the varistor 11 is formed by ion implantation. The device layer 13 includes microelectronic materials. The microelectronic materials included in the varistor 11 are the same as the microelectronic materials included in the device layer 13, which means that the varistor 11 is formed on the device layer 13.

[0053] Using the same microelectronic material can simplify the production process, reduce the steps of material conversion and processing, and thus improve production efficiency. At the same time, this compatibility also helps to ensure a good interface bonding between the varistor 11 and the device layer 13, and improve the overall performance of the device. At the same time, the same microelectronic material means that the varistor 11 and the device layer 13 have similar electrical and thermal properties, which helps to ensure the stability and reliability of the device under different working environments.

[0054] In some embodiments, there is a distance between the surface of the varistor 11 close to the buried oxide layer 14 and the buried oxide layer 14 , and there is also a distance between the bottom of the isolation trench 12 and the buried oxide layer 14 .

[0055] That is, the varistor 11 and the isolation trench 12 only occupy a portion of the device layer 13 . For example, the thickness of the device layer 13 is 10 μm, and the thickness of the varistor 11 and the isolation trench 12 is 1 μm.

[0056] like Figure 2 As shown, the first substrate layer 15 is provided with a through hole penetrating along the thickness direction thereof, and the first substrate layer 15 and the buried oxide layer 14 form a groove, and the groove is used to form a cavity N.

[0057] In some embodiments, the isolation groove 12 is extended along the contour of one side of the varistor 11 close to the center of the first substrate 10 .

[0058] like Figure 1 As shown, there are four varistors 11 arranged along the circumference of the first substrate 10 ; there are four isolation grooves 12 , and one isolation groove 12 is arranged around one side of a varistor 11 close to the center of the first substrate 10 .

[0059] That is to say, an isolation groove 12 is arranged around each varistor 11 .

[0060] like Figure 2 and Figure 3 As shown, in some embodiments, the width of the isolation trench 12 is greater than or equal to 10 μm and less than or equal to 50 μm.

[0061] Among them, the width of the isolation groove 12 is 10μm-50μm. There is a mutual diffusion problem in the double-fold resistor injection annealing process. If the width is too small, leakage between the two fold resistors is likely to occur through the area below the isolation groove, causing device failure; if the width is too large, stress concentration in the resistor area will occur, and the stress of the X-direction resistor and the Y-direction resistor will not match, affecting the linearity performance.

[0062] like Figure 1 and Figure 2 As shown, in some embodiments, the pressure sensing module 100 further includes: interconnecting wires 19 , which are electrically connected to the plurality of varistors 11 ; and the interconnecting wires 19 are arranged around the plurality of varistors 11 and the plurality of isolation slots 12 .

[0063] The first metal layer 16 is annular and connected to the non-cavity N portion of the first substrate layer 15 close to the side away from the buried oxide layer 14 ; the first connection layer 17 is connected to the first metal layer 16 on the side close to the first metal layer 16 , and is connected to the second substrate 20 on the side away from the first metal layer 16 .

[0064] The width of the first metal layer 16 is greater than 600 μm, the distance between the side of the first metal layer 16 away from the cavity N and the boundary of the first substrate 10 is greater than or equal to 50 μm, and the distance between the side of the first metal layer 16 close to the cavity N and the boundary of the cavity N is greater than 50 μm. The thickness of the first connection layer 17 is 10-60 μm.

[0065] The second substrate 20 includes a second base layer 21 , a second metal layer 22 and a second connection layer 23 .

[0066] The second metal layer 22 is annular, and the side of the second metal layer 22 away from the first substrate 10 is connected to the second substrate layer 21; the side of the second connection layer 23 away from the first substrate 10 is connected to the second metal layer 22, and the side close to the first substrate 10 is connected to the first substrate 10.

[0067] The width of the second metal layer 22 is greater than 600 μm, the distance between the side of the second metal layer 22 away from the cavity N and the boundary of the second substrate 20 is greater than 50 μm, and the distance between the side of the second metal layer 22 close to the cavity N and the boundary of the cavity N is greater than 50 μm. The thickness of the second connection layer 23 is 10-60 μm.

[0068] Exemplarily, the material of the first metal layer 16 or the second metal layer 22 may be a Cr / Au layer, a Ti / Cr / Au layer, a Cr / Ni / Au layer, or the like.

[0069] The first substrate 10 includes four varistors 11 and four metal pads 18 . The four varistors 11 are connected in series in sequence and are connected end to end to form a ring circuit.

[0070] Among them, the four varistors 11 are located at the center of the four membrane edges of the varistor film (refer to Figure 2 ), the four resistor film margins are consistent and the resistor film margin distance is a value between 0-20μm, the width of the four varistors 11 is the same as the total length, the fold number can be 1-10 folds, the upper and lower varistors 11 have the same structural dimensions, and the left and right varistors 11 have the same structural dimensions. In this application, it is two folds.

[0071] In some embodiments, Figure 4 As shown, the folding number of the varistor 11 is 6 folds.

[0072] Exemplarily, the material of the interconnection wire 19 may be a low resistivity material, such as any one or more combinations of Al, Ti / Al, Au and Cr / Au, so that a good circuit path can be formed.

[0073] In this way, the varistor 11 is located on the first substrate 10, the interconnection wire 19 is located on the first substrate 10, the varistor 11 and the interconnection wire 19 are electrically connected, and multiple metal pads 18 are connected to the middle section of the interconnection wire 19, that is, the four corners of the first substrate 10, thereby forming a Wheatstone bridge structure.

[0074] The Wheatstone bridge structure includes: an input terminal, two output terminals and a ground terminal.

[0075] It should be noted that the two output terminals of the Wheatstone bridge structure are located at opposite corners, and the positions of the input terminal and the ground terminal are not required.

[0076] The metal pad 18 may be in a square, rectangular, circular, elliptical or other structure, and the side length or straight dimension of the pad may be 50-150 μm.

[0077] In some embodiments, the first substrate layer 15 is an SOI substrate layer. The SOI substrate layer can be etched to the buried oxide layer 14 to form a cavity, or a portion of the substrate layer can be etched to form a cavity, and a pressure-sensitive film can be formed inside the cavity. Figure 3 The cavity is a square cavity N, and the side length of the cavity N can be: 500-2000μm.

[0078] Exemplarily, the material of the first substrate layer 15 may be silicon. The material of the buried oxide layer 14 may be an insulating material, such as any one or more combinations of SiO2, SiN and glass. In this case, the first substrate layer 15 and the buried oxide layer 14 may form a pressure-sensitive film.

[0079] That is to say, the region where the varistor 11 is located and the region where the varistor film is located are directly opposite to the orthographic projections of the multiple varistors 11 on the first substrate layer 15, and are located in the region where the varistor film is located. The first metal layer 16 and the first connecting layer 17 surround it from above, and the second metal layer 22 and the second connecting layer 23 surround it from below, and the second metal layer 22 and the second connecting layer 23 are fixed to the second substrate layer 21, so as to form a sealed or vacuum structure.

[0080] Exemplarily, the material of the first connection layer 17 or the second connection layer 23 may be a eutectic solder, for example, a combination of one or more of AuSn, AgSn, CuSn and SnAgCu.

[0081] In some embodiments, the first substrate 10 and the second substrate 20 enclose a vacuum chamber N.

[0082] In some embodiments, when the first substrate 10 and the second substrate 20 enclose a vacuum cavity N, the pressure sensing module 100 further includes a getter sheet located in the vacuum cavity N.

[0083] The above-mentioned pressure sensing module 100 is an absolute pressure sensing module 100, which can measure the absolute value of pressure change and has the advantages of high precision and large measurement range; however, the absolute pressure sensing module 100 is not suitable for some measurements of water pressure and air pressure, so a gauge pressure sensing module 100 is proposed as follows: In some embodiments, the second substrate layer 21 is provided with through holes; the through holes can connect the back side of the diaphragm to the outside atmosphere, so as to achieve gauge pressure / differential pressure measurement of the pressure sensing module 100 .

[0084] Here, there is no limitation on the size of the through hole. In some examples, the aperture of the through hole 50 ranges from 0 to 100 μm, such as 0 μm, 10 μm, 30 μm, 50 μm, 70 μm or 100 μm.

[0085] For example, an insulating layer (not shown in the figure) may be provided on the side wall of the through hole, so that the safety and reliability of the pressure sensing module 100 may be improved.

[0086] It can be understood that the gauge pressure cavity N is the aforementioned cavity N. The through hole 50 can be used to connect the gauge pressure cavity N to the external atmospheric environment, so that the pressure of the gauge pressure cavity N is equal to the external pressure. Moreover, when the first substrate 10 and the second substrate 20 are enclosed to form the gauge pressure cavity N, the pressure sensing module 100 is a gauge pressure type pressure sensing module 100, which can be measured with atmospheric pressure as a reference object, has the advantage of being easy to prepare, and can be used to measure the relative pressure change values ​​of media such as water pressure and air pressure.

[0087] like Figure 5 and Figure 6 As shown, some embodiments of the present disclosure further provide a pressure sensor 200. The pressure sensor 200 includes a pressure sensing module 100 and an integrated circuit 150 provided by the above technical solution.

[0088] The integrated circuit 150 is electrically connected to the metal pad 18 of the pressure sensing module 100 .

[0089] It is understandable that the varistor 11 generates a voltage signal when receiving pressure, and transmits the voltage signal to the integrated circuit 150, which can further process the voltage signal and output it to a digital signal to feedback the pressure. In this way, the transmission of pressure measurement data can be achieved.

[0090] like Figure 7 As shown, some embodiments of the present disclosure further provide an electronic device 300. The electronic device 300 includes a housing 310 and a pressure sensor 200 disposed on the housing 310.

[0091] In some examples, the electronic device 300 may be a mobile phone or a computer; it may also be a portable electronic device 300, so that the pressure sensing module 100 can be applied to technical scenarios such as automobiles and process production that require pressure measurement.

[0092] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit it. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A pressure sensing module, characterized in that: It comprises a first substrate and a second substrate which are arranged opposite to each other, and a cavity is formed between the first substrate and the second substrate; A varistor and an isolation groove are provided on a side of the first substrate away from the second substrate, and the isolation groove is provided around at least a portion of the varistor.

2. The pressure sensing module according to claim 1, characterized in that: The first substrate comprises a first substrate layer, a buried oxide layer and a device layer which are sequentially stacked in a direction away from the second substrate; The varistor and the isolation groove are arranged in the device layer, and the notch of the isolation groove is located on the surface of the device layer away from the buried oxide layer.

3. The pressure sensing module according to claim 2, characterized in that: A surface of the varistor facing away from the buried oxide layer is flush with a surface of the device layer facing away from the buried oxide layer.

4. The pressure sensing module according to claim 2, characterized in that: The varistor includes a microelectronic material and doping ions, the device layer includes a microelectronic material, and the microelectronic material included in the varistor is the same as the microelectronic material included in the device layer.

5. The pressure sensing module according to claim 2, characterized in that: There is a distance between the surface of the varistor close to the buried oxide layer and the buried oxide layer, and there is also a distance between the bottom of the isolation trench and the buried oxide layer; Wherein, the isolation groove is formed by etching on the device layer.

6. The pressure sensing module according to claim 2, characterized in that: The first substrate layer is provided with a through hole penetrating along the thickness direction thereof, and the first substrate layer and the buried oxide layer form a groove, and the groove is used to form the cavity.

7. The pressure sensing module according to any one of claims 1 to 6, characterized in that: Along the thickness direction of the first substrate, the size of the varistor is less than or equal to the depth of the isolation groove.

8. The pressure sensing module according to any one of claims 1 to 6, characterized in that: The isolation groove is extended along the contour of one side of the varistor close to the center of the first substrate.

9. The pressure sensing module according to any one of claims 1 to 6, characterized in that: The number of the varistors is four, and they are arranged along the circumference of the first substrate; The number of the isolation grooves is four, and one isolation groove is arranged around one side of the varistor close to the center of the first substrate.

10. The pressure sensing module according to any one of claims 1 to 6, characterized in that: The width of the isolation trench is greater than or equal to 10 μm and less than or equal to 50 μm.

11. The pressure sensing module according to any one of claims 1 to 6, characterized in that: The depth of the isolation trench is greater than or equal to 0.4 μm and less than or equal to 1.2 μm.

12. The pressure sensing module according to any one of claims 1 to 6, characterized in that: The pressure sensing module further includes: interconnecting wires, which are electrically connected to the plurality of varistors; and the interconnecting wires are arranged around the plurality of varistors and the plurality of isolation grooves.

13. A pressure sensor, characterized in that: include: The pressure sensing module according to any one of claims 1 to 12; The integrated circuit is electrically connected to the pressure sensing module.

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