A MEMS piezoresistive pressure sensor and a method for manufacturing the same
Through the combination of the three-layer pressure-sensitive film design and the gas buffer cavity, the problem of linearity and temperature drift of the piezoresistive pressure sensor in a wide pressure range is solved, and the balance of high sensitivity and high linearity is achieved, and the vacuum cavity is passed. The design improves the temperature drift problem and improves the measurement accuracy.
Patent Information
- Application Number
- CN202410867038.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2024-07-01
- Publication Date
- 2024-12-13
- Estimated Expiration
- 2044-07-01
AI Technical Summary
Existing piezoresistive pressure sensors have poor linearity over a wide pressure range, and because temperature drift affects measurement accuracy, it is difficult to find a balance between high sensitivity and linearity.
Designed with a three-layer pressure-sensitive film, where the intermediate layer is thicker than the top layer, a gas buffer cavity and a vacuum cavity are set, and the gas buffer cavity is filled with inert gas, and assembled by anode bonding technology to ensure that the film provides linear response within the optimal working range. , and suppresses temperature drift by design of the vacuum cavity.
The linear working range of the sensor is widened, the nonlinear response caused by pressure spikes is eliminated, and the temperature drift problem is improved through temperature compensation, improving measurement accuracy and overall performance of the sensor.
Smart Images
Figure CN118392382B_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of pressure sensors, and in particular relates to a MEMS (Micro-Electro-Mechanical System) piezoresistive pressure sensor and a preparation method thereof. Background Art
[0002] A pressure sensor is a device that can convert pressure signals into electrical signals. It has been widely used in industrial control, medical electronics, environmental monitoring, aerospace and other fields. Among the many different types of pressure sensors, piezoresistive pressure sensors have good linearity and reliability, simple structure and preparation, and low cost. They are currently one of the most widely used pressure sensors. Piezoresistive pressure sensors use the piezoresistive effect of semiconductor materials to form a Wheatstone bridge by interconnecting piezoresistors to convert ambient pressure into electrical signals to measure pressure.
[0003] The common piezoresistive pressure sensors at present are mainly based on pressure-sensitive film structures, and the piezoresistors are distributed on the surface of the film. In order to improve the sensitivity of the sensor, the thickness of the sensitive film is designed to be very thin, so as to ensure that a larger deformation and stress are obtained under the same pressure conditions, thereby increasing the resistance change of the piezoresistors and the electrical output. However, when the piezoresistance film is subjected to a large pressure, the deformation and stress exceed the provisions of the small deflection theory, and the linearity of the sensor output cannot be guaranteed, so that the linearity of the piezoresistive pressure sensor is poor in a wide pressure range; in addition, since the piezoresistance coefficient of the piezoresistors will change due to the influence of the ambient temperature, the output of the sensor will drift (i.e., temperature drift), which affects the test accuracy of the sensor. Summary of the invention
[0004] Purpose of the invention: In view of the above-mentioned prior art, a MEMS piezoresistive pressure sensor and a preparation method thereof are proposed to broaden the linear working range of the sensor and improve the temperature drift suppression capability of the sensor.
[0005] Technical solution: A MEMS piezoresistive pressure sensor comprises three layers of pressure-sensitive films from top to bottom, wherein the thickness of the middle layer of pressure-sensitive film is greater than that of the top layer of pressure-sensitive film, and a piezoresistor is provided on the upper surface of each layer of pressure-sensitive film; a gas buffer cavity is provided between the top layer of pressure-sensitive film and the middle layer of pressure-sensitive film, and vacuum cavities are provided between the middle layer of pressure-sensitive film and the bottom layer of pressure-sensitive film and between the bottom layer of pressure-sensitive film and the bottom substrate of the sensor, respectively; the projections of the three layers of pressure-sensitive film, the gas buffer cavity, and the vacuum cavity in the thickness direction all coincide with each other.
[0006] Furthermore, each layer of the pressure-sensitive film is provided with four varistors arranged in the same direction, and the projections of the four varistors on each layer of the pressure-sensitive film in the thickness direction of the pressure-sensitive film overlap.
[0007] Furthermore, the gas buffer chamber is filled with an inert gas; the inert gas includes argon.
[0008] Furthermore, the pressure-sensitive film is rectangular, and the four varistors are respectively arranged at the center positions of the four edges of the pressure-sensitive film.
[0009] The method for preparing the MEMS piezoresistive pressure sensor comprises:
[0010] Providing a first substrate, and forming a first varistor on the upper surface of the first substrate;
[0011] Forming a groove on the lower surface of the first substrate to release a first pressure-sensitive film of a preset thickness;
[0012] providing a second substrate and a third substrate;
[0013] forming a second varistor on the upper surface of the second substrate; forming a third varistor on the upper surface of the third substrate;
[0014] Grooves are formed on the lower surface of the second substrate and the lower surface of the third substrate respectively to release the second pressure-sensitive film and the third pressure-sensitive film of preset thickness;
[0015] Laminating the lower surface of the second substrate and the upper surface of the third substrate under vacuum conditions to form a second vacuum chamber;
[0016] Bonding the lower surface of the first substrate to the upper surface of the second substrate by anodic bonding in an inert atmosphere to form a gas buffer cavity;
[0017] Providing a fourth substrate; bonding the lower surface of the third substrate to the fourth substrate under vacuum conditions to form a third vacuum chamber;
[0018] A passivation layer is formed on the upper surfaces of the first varistor and the first varistor.
[0019] An electronic device comprises the MEMS piezoresistive pressure sensor.
[0020] Beneficial effects: The present invention adopts a three-layer pressure-sensitive film design, sets the thickness of the middle layer pressure-sensitive film to be greater than that of the top layer pressure-sensitive film, and combines the design of the gas buffer cavity, so that the two layers of film around the gas buffer cavity can provide near-linear response within their optimal working range, and broadens the linear working range of the sensor without affecting the sensitivity of the sensor. In addition, the elastic gas chamber can also effectively alleviate local pressure spikes, thereby eliminating the nonlinear response caused by the peak pressure.
[0021] The projections of the three-layer pressure-sensitive film, the gas buffer cavity and the vacuum cavity in the thickness direction all overlap, thus minimizing the introduction of other variables that may affect pressure sensing and ensuring the accuracy of sensing.
[0022] Since the vacuum cavity does not conduct external pressure, the resistance change of the varistor on the bottom varistor film can be used as a temperature compensation for the resistance of the varistor on the upper two varistor films, thereby improving the temperature drift suppression capability of the sensor. BRIEF DESCRIPTION OF THE DRAWINGS
[0023] Figure 1-Figure 10 A schematic diagram of the structure of a MEMS piezoresistive pressure sensor preparation process according to an embodiment of the present invention;
[0024] Fig.11 A schematic top view of the arrangement of piezoresistors of a piezoresistive pressure sensor disclosed in an embodiment;
[0025] In the figure: 1-fourth substrate; 2-third substrate; 3-third vacuum cavity; 4-third piezoresistance film; 5-third piezoresistance; 6-second substrate; 7-second vacuum cavity; 8-second piezoresistance film; 9-second piezoresistance; 10-first substrate; 11-gas buffer cavity; 12-first piezoresistance film; 13-first piezoresistance; 14-passivation layer. DETAILED DESCRIPTION
[0026] The following is a further detailed description of the implementation methods of the present application in conjunction with the accompanying drawings and examples. The detailed descriptions and drawings of the following examples are used to illustrate the principles of the present application, but cannot be used to limit the scope of the present application, that is, the present application is not limited to the described embodiments. In the description of the present application, it should be noted that, unless otherwise specified, the meaning of "multiple" is more than two; the orientation or position relationship indicated by the terms "upper", "lower", "left", "right", "inside", "outside", etc. is only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present application. In addition, the terms "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance. "Vertical" is not vertical in the strict sense, but within the error tolerance range. "Parallel" is not parallel in the strict sense, but within the error tolerance range.
[0027] In the description of this application, it should also 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 directly connected or indirectly connected through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to the specific circumstances.
[0028] A MEMS piezoresistive pressure sensor, such as Figure 10-11 As shown, Fig.11 is a top view schematic diagram of the arrangement of piezoresistors of the piezoresistive pressure sensor disclosed in the present invention, Fig.10 For along Fig.11 The pressure sensor comprises a fourth substrate 1, a third substrate 2, a second substrate 6, a first substrate 10 and a passivation layer 14 which are stacked in sequence.
[0029] A third vacuum chamber 3 is provided between the fourth substrate 1 and the third substrate 2, a second vacuum chamber 7 is provided between the third substrate 2 and the second substrate 6, and a gas buffer chamber 11 is provided between the second substrate 6 and the first substrate 10. A third pressure-sensitive film 4 is provided at the third substrate 2 corresponding to the third vacuum chamber 3, and a third varistor 5 is provided on the third pressure-sensitive film 4. A second pressure-sensitive film 8 is provided at the second substrate 6 corresponding to the second vacuum chamber 7, and a second varistor 9 is provided on the second pressure-sensitive film 8. A first pressure-sensitive film 12 is provided at the first substrate 10 corresponding to the gas buffer chamber 11, and a first varistor 13 is provided on the first pressure-sensitive film 12. The first pressure-sensitive film 12 and the second pressure-sensitive film 8 have different thicknesses, and the second pressure-sensitive film 8 has a thickness greater than that of the first pressure-sensitive film 12.
[0030] The first substrate 10, the first pressure-sensitive film 12 and the second pressure-sensitive film 8 together form a gas buffer chamber 11. The second substrate 6, the second pressure-sensitive film 8 and the third pressure-sensitive film 4 together form a second vacuum chamber 7. The third substrate 2, the third pressure-sensitive film 4 and the fourth substrate 1 together form the third vacuum chamber 3. The projection of the gas buffer chamber 11 in the thickness direction coincides with the projection of the second vacuum chamber 7 and the third vacuum chamber 3. It can be understood that the thickness direction is the thickness direction of the first substrate 10. The gas buffer chamber 11 is filled with an inert gas.
[0031] In some embodiments, there are four third varistors 5, and the four third varistors 5 are arranged on the upper surface of the third varistors 4. The third varistors 4 are rectangular, wherein the four third varistors 5 are respectively arranged at the center positions of the four sides of the third varistors 4, and the four third varistors 5 are arranged in the same direction. There are four second varistors 9, and the four second varistors 9 are arranged on the upper surface of the second varistors 8. The second varistors 8 are rectangular, wherein the four second varistors 9 are respectively arranged at the center positions of the four sides of the second varistors 8, and the four second varistors 9 are arranged in the same direction. There are four first varistors 13, and the four first varistors 13 are arranged on the upper surface of the first varistors 12. The first varistors 12 are rectangular, wherein the four first varistors 13 are respectively arranged at the center positions of the four sides of the first varistors 12, and the four first varistors 13 are arranged in the same direction. The projection of the first varistors 13 in the thickness direction coincides with the second varistors 9 and the third varistors 5. It can be understood that the thickness direction is the thickness direction of the fourth substrate 1. Four varistors are arranged on each layer of the varistor film to form a Wheatstone bridge.
[0032] In some embodiments, the fourth substrate 1 is made of single crystal silicon or glass, and has a thickness of 200-1000 μm.
[0033] In some embodiments, the third substrate 2 is made of single crystal silicon with a thickness of 200-2000 μm. The central thin layer on the upper surface of the third substrate 2 is set as a third pressure-sensitive film 4 with a thickness of 1-50 μm.
[0034] In some embodiments, the second substrate 6 is made of single crystal silicon with a thickness of 200-2000 μm. The central thin layer on the upper surface of the second substrate 6 is set as the second pressure-sensitive film 8 with a thickness of 1-50 μm.
[0035] In some embodiments, the first substrate 10 is made of single crystal silicon with a thickness of 50-1000 μm. The central thin layer on the upper surface of the first substrate 10 is provided as a first pressure-sensitive film 12 with a thickness of 1-20 μm.
[0036] In some embodiments, four third varistors 5 are arranged on the upper surface of the third varistors 4, and the four third varistors 5 are respectively R1'', R2'', R3'' and R4''. Four second varistors 9 are arranged on the upper surface of the second varistors 8, and the four second varistors 9 are respectively R1', R2', R3' and R4', and their projections in the thickness direction coincide with the four third varistors 5 respectively. Four first varistors 13 are arranged on the upper surface of the first varistors 12, and the four first varistors 13 are respectively R1, R2, R3 and R4, and their projections in the thickness direction coincide with the four second varistors 9 and the third varistors 5 respectively. Among them, the thickness direction is the thickness direction of the varistors.
[0037] In some embodiments, a passivation layer 14 is disposed on the upper surface of the first piezoresistors 13 and the first piezoresistors 12. The passivation layer 14 is made of silicon dioxide or silicon nitride and has a thickness of 50-1000 nm. The passivation layer 14 is used to protect the first piezoresistors 13 to improve the stability of the sensor.
[0038] In the present disclosure, the third piezoresistance film 4 is located above the second vacuum chamber 7. The external pressure will not cause the resistance of the third piezoresistance 5 to change, but it will change due to the change of the external environment temperature. The change of the resistance of the third piezoresistance 5 is used as the compensation of the resistance of the first piezoresistance 13 and the second piezoresistance 9 with respect to temperature, which can improve the temperature drift suppression capability of the sensor.
[0039] In the present disclosure, the thicknesses of the first pressure-sensitive film 12 and the second pressure-sensitive film 8 are set to be different. According to the linear principle, when the pressure-sensitive film is subjected to force, in order to ensure that the chip has good linearity within the entire wide range, the deformation of the film must satisfy the small deflection theorem, that is, the maximum deformation of the center of the film does not exceed 1 / 5 of the thickness of the film, but the increase in the thickness of the pressure-sensitive film will reduce the sensitivity of the sensor. In order to enable the sensor to achieve high linear output on the basis of meeting the sensitivity within a wide pressure range, pressure-sensitive films of different thicknesses are used, wherein the thickness of the second pressure-sensitive film 8 is greater than the thickness of the first pressure-sensitive film 12, that is, the thickness of the first pressure-sensitive film 12 is relatively thin, and it works in the linear output range at low pressure, and the thickness of the second pressure-sensitive film 8 is relatively thick, and it works in the linear output range at high pressure. In the present disclosure, the combination of pressure-sensitive films of different thicknesses improves the linearity of the piezoresistive pressure sensor within a wide pressure range.
[0040] The gas buffer chamber 11 is filled with an inert gas to ensure that the first pressure-sensitive film 12 and the second pressure-sensitive film 8 are subjected to uniform force. In addition, the elastic gas buffer chamber 11 can effectively alleviate local pressure spikes, which will cause nonlinear response in a single film sensor.
[0041] The working principle of a MEMS piezoresistive pressure sensor provided by this invention is as follows:
[0042] The third piezoresistor 4, the third piezoresistor 5, the second vacuum chamber 7, the second piezoresistor 8, the second piezoresistor 9, the gas buffer chamber 11, the first piezoresistor 12 and the first piezoresistor 13 constitute the piezoresistive pressure sensor of the present invention. The piezoresistor itself is affected by the external temperature. The first piezoresistor 13, the second piezoresistor 9 and the third piezoresistor 5 undergo the same changes due to the external temperature. Due to the existence of the second vacuum chamber 7, the resistance of the third piezoresistor 5 is not affected by the external pressure and only changes with the temperature. The change in the resistance of the third piezoresistor 5 is used as compensation for the resistance of the first piezoresistor 13 and the second piezoresistor 9 with respect to temperature, which can improve the temperature drift suppression capability of the pressure sensor.
[0043] Furthermore, due to the presence of the gas buffer chamber 11, the first pressure-sensitive film 12 and the second pressure-sensitive film 8 are subjected to the same pressure and deform under external pressure. Based on the piezoresistive effect, the resistance values of the piezoresistors located on the two sensitive films change accordingly. Among them, the four first piezoresistors 13 constitute a first Wheatstone bridge, and the four second piezoresistors 9 constitute a second Wheatstone bridge, which convert the pressure signal into an electrical signal, thereby realizing pressure detection.
[0044] Furthermore, since the thickness of the first pressure-sensitive film 12 and the second pressure-sensitive film 8 are different, when the external pressure is small, the output of the thinner first pressure-sensitive film 12 is linear. At this time, the output of the first Wheatstone bridge is used as the output of the sensor; when the external pressure exceeds the linear working range of the first pressure-sensitive film 12, the thicker second pressure-sensitive film 8 works in the linear region. At this time, the output of the second Wheatstone bridge is used as the output of the sensor, thereby ensuring that the sensor has high linearity within a wide pressure range.
[0045] In summary, compared with the prior art, the present disclosure has the following advantages:
[0046] 1. The present disclosure adopts a three-layer pressure-sensitive film design, combined with a gas buffer chamber 11 design, so that the two layers of film around the gas buffer chamber 11 can provide near-linear response within its optimal working range, and broaden the linear working range of the sensor without affecting the sensitivity of the sensor. In addition, the elastic gas chamber can effectively alleviate local pressure spikes, thereby eliminating the nonlinear response caused by the peak pressure.
[0047] 2. The present disclosure adds a third varistor 5 that is only affected by temperature to compensate for the temperature drift of the two-layer film working under stress in a wide pressure range, thereby improving the temperature drift suppression capability of the sensor.
[0048] 3. The present invention adopts three layers of pressure-sensitive film and arranges them in a vertical manner. On the basis of not changing the chip area, the linearity of the sensor is improved, the structure is compact, and the integration is high.
[0049] 4. The present disclosure is prepared using MEMS technology, and the sensor has the advantages of high precision, good consistency, easy batch production and low cost.
[0050] A second aspect of the embodiments of the present disclosure provides a method for preparing a MEMS piezoresistive pressure sensor, the method for preparing the above-mentioned MEMS piezoresistive pressure sensor comprising:
[0051] S101: providing a third substrate 2 and a second substrate 6.
[0052] S102 : forming a third varistor 5 on the upper surface of the third substrate 2 , and forming a second varistor 9 on the upper surface of the second substrate 6 .
[0053] S103: forming grooves on the lower surface of the third substrate 2 and the lower surface of the second substrate 6, and releasing the third pressure-sensitive film 4 and the second pressure-sensitive film 8 of a preset thickness.
[0054] S104 : Laminating the lower surface of the second substrate 6 and the upper surface of the third substrate 2 under vacuum conditions to form a second vacuum chamber 7 .
[0055] S105 : providing a first substrate 10 , and forming a first varistor 13 on the upper surface of the first substrate 10 .
[0056] S106: forming a groove on the lower surface of the first substrate 10 and releasing the first pressure-sensitive film 12 with a preset thickness.
[0057] S107 : in an inert atmosphere, the lower surface of the first substrate 10 is bonded to the upper surface of the second substrate 6 by anodic bonding to form a gas buffer cavity 11 .
[0058] S108 : forming a passivation layer 14 on the upper surfaces of the first varistor 12 and the first varistor 13 .
[0059] S109: providing a fourth substrate 1, and bonding the lower surface of the third substrate 2 to the fourth substrate 1 under vacuum conditions to form a third vacuum chamber 3.
[0060] refer to Figure 1-Figure 10 The present disclosure provides a specific example of a method for preparing a MEMS piezoresistive pressure sensor, comprising:
[0061] Step 1: Select two 300 mm thick N-type (100) silicon wafers as the third substrate 2 and the second substrate 6, such as Figure 1 shown.
[0062] Step 2: Four third varistors 5 are prepared on the upper surface of the third substrate 2, and four second varistors 9 are prepared on the upper surface of the second substrate 6 by photolithography and boron ion implantation. Figure 2 shown.
[0063] Step 3: Form grooves on the lower surface of the third substrate 2 and the lower surface of the second substrate 6 by photolithography and DRIE (Deep Reactive Ion Etching), respectively, to release the third pressure-sensitive film 4 and the second pressure-sensitive film 8 with a thickness of 40 mm, as shown in FIG. Figure 3 shown.
[0064] Step 4: Under vacuum conditions, the lower surface of the second substrate 6 is closely attached to the upper surface of the third substrate 2 by anodic bonding to form a second vacuum chamber 7, such as Figure 4 shown.
[0065] Step 5: Select a 100 mm thick N-type (100) silicon wafer as the first substrate 10, such as Figure 5 shown.
[0066] Step 6: Four first varistors 13 are prepared on the upper surface of the first substrate 10 by photolithography and boron ion implantation. Figure 6 shown.
[0067] Step 7: A groove is formed on the lower surface of the first substrate 10 by photolithography and DRIE (Deep Reactive Ion Etching) to release the first pressure-sensitive film 12 with a thickness of 10 mm. Figure 7 shown.
[0068] Step 8: In an Ar atmosphere, the lower surface of the first substrate 10 is closely attached to the upper surface of the second substrate 6 by anodic bonding to form a gas buffer cavity 11, such as Figure 8 shown.
[0069] Step 9: Prepare a 300 nm thick silicon dioxide as a passivation layer 14 on the first varistor film 12 and the four first varistors 13 by PECVD. Fig. 9 shown.
[0070] Step 10: Select a 500 mm thick BF33 glass sheet as the fourth substrate 1, and under vacuum conditions, closely attach the lower surface of the third substrate 2 to the fourth substrate 1 by anodic bonding to form a third vacuum chamber 3, such as Fig.10 shown.
[0071] According to a third aspect of an embodiment of the present disclosure, an electronic device is provided, and the electronic device includes the above-mentioned MEMS piezoresistive pressure sensor.
[0072] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.
Claims
1. A MEMS piezoresistive pressure sensor, It is characterized in that The sensor comprises three layers of pressure-sensitive films from top to bottom, wherein the thickness of the middle layer of pressure-sensitive film is greater than that of the top layer of pressure-sensitive film, and a varistor is provided on the upper surface of each layer of pressure-sensitive film; a gas buffer cavity is provided between the top layer of pressure-sensitive film and the middle layer of pressure-sensitive film, and vacuum cavities are provided between the middle layer of pressure-sensitive film and the bottom layer of pressure-sensitive film, and between the bottom layer of pressure-sensitive film and the bottom substrate of the sensor, respectively; the projections of the three layers of pressure-sensitive film, the gas buffer cavity, and the vacuum cavity in the thickness direction all coincide; the resistance change of the varistor on the bottom layer of pressure-sensitive film is used as the temperature compensation of the resistance of the varistor on the upper two layers of pressure-sensitive film; due to the different thicknesses of the top layer of pressure-sensitive film and the middle layer of pressure-sensitive film, the thinner top layer of pressure-sensitive film works in the linear output range at low pressure, and the thicker middle layer of pressure-sensitive film works in the linear output range at high pressure.
2. The MEMS piezoresistive pressure sensor according to claim 1, It is characterized in that Each layer of the pressure-sensitive film is provided with four varistors arranged in the same direction, and the projections of the four varistors on each layer of the pressure-sensitive film in the thickness direction of the pressure-sensitive film overlap.
3. The MEMS piezoresistive pressure sensor according to claim 1 or 2, It is characterized in that The gas buffer chamber is filled with an inert gas; the inert gas includes argon.
4. The MEMS piezoresistive pressure sensor according to claim 2, It is characterized in that The pressure-sensitive film is rectangular, and the four varistors are respectively arranged at the center positions of the four edges of the pressure-sensitive film.
5. A method for preparing a MEMS piezoresistive pressure sensor according to any one of claims 1 to 4, It is characterized in that include: Providing a first substrate, and forming a first varistor on the upper surface of the first substrate; Forming a groove on the lower surface of the first substrate to release a first pressure-sensitive film of a preset thickness; providing a second substrate and a third substrate; forming a second varistor on the upper surface of the second substrate; forming a third varistor on the upper surface of the third substrate; Grooves are formed on the lower surface of the second substrate and the lower surface of the third substrate respectively to release the second pressure-sensitive film and the third pressure-sensitive film of preset thickness; Laminating the lower surface of the second substrate and the upper surface of the third substrate under vacuum conditions to form a second vacuum chamber; In an inert atmosphere, the lower surface of the first substrate is bonded to the upper surface of the second substrate by anodic bonding to form a gas buffer cavity; Providing a fourth substrate; bonding the lower surface of the third substrate to the fourth substrate under vacuum conditions to form a third vacuum chamber; A passivation layer is formed on the upper surfaces of the first varistor and the first varistor.
6. An electronic device, It is characterized in that The electronic device comprises the MEMS piezoresistive pressure sensor according to any one of claims 1-4.