Pressure sensing chip, pressure sensor and calibration method of pressure sensor

Abstract

The invention provides a pressure sensing chip, a pressure sensor and a calibration method of the pressure sensor, and relates to the technical field of pressure sensors. The pressure sensing chip comprises an upper substrate, a lower substrate and a piezoresistor; the upper substrate and the lower substrate are oppositely arranged, the upper substrate and the lower substrate are made of conductive materials, and the upper substrate and the lower substrate are insulated from each other; the upper substrate comprises a pressure sensing film, and a closed pressure sensing cavity is formed between the pressure sensing film and the lower substrate; the piezoresistor is connected to the pressure sensing film, the piezoresistor is insulated from the pressure sensing film, and the resistance value of the piezoresistor is changed when the pressure sensing film deforms.

Description

Technical Field

[0001] The present disclosure relates to the field of pressure sensing technology, and in particular to a pressure sensing chip, a pressure sensor, and a pressure sensor calibration method. Background Art

[0002] A pressure sensor is a device that can convert pressure into an electrical signal. Pressure sensors can be divided into piezoresistive, capacitive, resonant, piezoelectric, etc. Among them, piezoresistive pressure sensors are widely used in the automotive, industrial control, consumer electronics, construction, and medical fields because of their good stability, low manufacturing cost, and compatibility with COMS processes. They are the most widely used MEMS pressure sensors at this stage.

[0003] However, the pressure sensor is prone to reduced accuracy after being used for a period of time, and the pressure sensor needs to be disassembled for calibration, which is inconvenient to operate. Summary of the invention

[0004] The embodiments of the present disclosure provide a pressure sensing chip, a pressure sensor, and a pressure sensor calibration method, which makes the calibration of the pressure sensor more convenient.

[0005] To achieve the above objectives, the embodiments of the present disclosure adopt the following technical solutions:

[0006] On the one hand, a pressure sensing chip is provided, comprising an upper substrate, a lower substrate and a piezoresistor;

[0007] The upper substrate and the lower substrate are arranged opposite to each other, the upper substrate and the lower substrate are made of conductive materials, and the upper substrate and the lower substrate are insulated from each other;

[0008] The upper substrate includes a pressure-sensitive film, and a closed pressure-sensitive cavity is provided between the pressure-sensitive film and the lower substrate;

[0009] The varistor is connected to the pressure-sensitive film, and the varistor is insulated from the pressure-sensitive film. When the pressure-sensitive film is deformed, the resistance value of the varistor changes.

[0010] In some embodiments, the pressure sensor chip further includes an upper electrode and a lower electrode, the upper electrode is electrically connected to the upper substrate, the lower electrode is electrically connected to the lower substrate, and the upper electrode and the lower electrode are located on a side of the upper substrate away from the lower substrate.

[0011] In some embodiments, a second overlap structure is provided in the upper substrate, and the second overlap structure penetrates the upper substrate in a direction perpendicular to the upper substrate, one end of the second overlap structure is electrically connected to the lower electrode, and the other end of the second overlap structure is electrically connected to the lower substrate, and the overlap structure is insulated from the upper substrate.

[0012] In some embodiments, the upper substrate is provided with a second via hole, the second via hole penetrates the upper substrate in a direction perpendicular to the upper substrate, the second overlapping structure is arranged in the second via hole, and a first insulating layer is provided between the second overlapping structure and the inner wall of the second via hole.

[0013] In some embodiments, a second insulating layer is provided on a side of the upper substrate away from the lower substrate, and the upper electrode, the lower electrode, and the varistor are connected on a side of the second insulating layer away from the lower substrate.

[0014] In some embodiments, the pressure sensing chip includes a plurality of the piezoresistors, and the plurality of the piezoresistors are connected to form a Wheatstone bridge.

[0015] In some embodiments, the lower substrate is oxidized toward the side of the upper substrate to form the third insulating layer, and the upper substrate and the third insulating layer are bonded; or, the upper substrate is oxidized toward the side of the lower substrate to form the third insulating layer, and the lower substrate and the third insulating layer are bonded.

[0016] On the other hand, a pressure sensor is provided, comprising a control chip and a pressure sensing chip as claimed in any one of claims 1 to 7, wherein the piezoresistor, the upper substrate and the lower substrate of the pressure sensing chip are electrically connected to the control chip.

[0017] On the other hand, a pressure sensor calibration method is provided, which is used to calibrate the pressure sensor, characterized in that the calibration method includes:

[0018] Acquire a test output value of the pressure sensor; the test output value is: an output value of the pressure sensor when the pressure-sensitive film undergoes a test deformation amount;

[0019] Acquire a theoretical output value of the pressure sensor; the theoretical output value is: an output value corresponding to the test deformation amount in a preset mapping relationship of the pressure sensor;

[0020] The output value of the pressure sensor is compensated according to the test output value and the theoretical output value.

[0021] In some implementations, obtaining a test output value of the pressure sensor includes:

[0022] A test voltage is applied to the upper substrate and the lower substrate; the pressure-sensitive film undergoes the test deformation amount under the action of the test voltage;

[0023] An output value of the pressure sensor is obtained as a test output value.

[0024] In some embodiments, when acquiring the test output value, the pressure-sensitive film is not subjected to external force.

[0025] In some implementations, obtaining the theoretical output value of the pressure sensor includes:

[0026] Acquire a test capacitance value; the test capacitance value is a capacitance value between the upper substrate and the lower substrate when the pressure-sensitive film undergoes the test deformation amount;

[0027] A theoretical output value corresponding to the test capacitance value is determined according to the mapping relationship.

[0028] The pressure sensing chip, pressure sensor and pressure sensor calibration method provided by the embodiments of the present disclosure are that the upper substrate and the lower substrate are arranged relative to each other and insulated, that is, the pressure-sensitive film and the lower substrate are arranged relative to each other and insulated. Since the pressure-sensitive film and the lower substrate are both made of conductive materials, the pressure-sensitive film and the lower substrate form an equivalent capacitor. When the pressure-sensitive film is deformed by the action of the force, the electrical parameters of the equivalent capacitor change, and as the deformation amount continues to change, the electrical parameters of the equivalent capacitor change continuously, that is, there is a corresponding relationship between the deformation amount of the pressure-sensitive film and the electrical parameters of the equivalent capacitor. Since there is a corresponding relationship between the deformation amount of the pressure-sensitive film and the magnitude of the force, there is a corresponding relationship between the magnitude of the force and the electrical parameters of the equivalent capacitor. When calibrating the pressure sensing chip, the magnitude of the force can be calculated by the electrical parameters of the equivalent capacitor, so as to calibrate the output value of the sensor chip, making the calibration of the sensor chip more convenient. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the embodiments of the present disclosure or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present disclosure. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0030] Figure 1 A schematic diagram of an electronic device is exemplarily shown;

[0031] Figure 2 The structural block diagram of an electronic device is exemplarily shown;

[0032] Figure 3A cross-sectional view of a pressure sensor is exemplarily shown;

[0033] Figure 4 It is a cross-sectional view of a pressure sensor chip in the initial state in the related art;

[0034] Figure 5 It is a cross-sectional view of a pressure sensor chip in the related art under external pressure;

[0035] Figure 6 A cross-sectional view of a pressure sensor chip is shown exemplarily;

[0036] Figure 7 The connection relationship diagram of multiple varistors is exemplarily shown;

[0037] Figures 8 to 13 The diagram exemplarily shows a process diagram of preparing a pressure sensor chip;

[0038] Fig.14 A flowchart of a pressure sensor calibration method is shown by way of example. DETAILED DESCRIPTION

[0039] The following will be combined with the drawings in the embodiments of the present disclosure to clearly and completely describe the technical solutions in the embodiments of the present disclosure. Obviously, the described embodiments are only part of the embodiments of the present disclosure, not all of the embodiments. Based on the embodiments in the present disclosure, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present disclosure.

[0040] In the embodiments of the present disclosure, words such as "first", "second", "third", and "fourth" are used to distinguish between identical or similar items with substantially the same functions and effects. This is only for the purpose of clearly describing the technical solutions of the embodiments of the present disclosure and shall not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features.

[0041] In the embodiments of the present disclosure, “plurality” means two or more than two, and “at least one” means one or more than one, unless otherwise clearly and specifically defined.

[0042] In the embodiments of the present disclosure, the orientation or positional relationship indicated by the terms "upper" and "lower" etc. is based on the orientation or positional relationship shown in the accompanying drawings and is only for the convenience of describing the present disclosure 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 disclosure.

[0043] An embodiment of the present disclosure provides an electronic device, which may be a terminal consumer product (for example, an unmanned aerial vehicle, an unmanned ship, a robot, etc.) or a 3C electronic product (for example, a mobile phone, a portable computer, a tablet computer, an e-reader, a laptop computer, a digital camera, a wearable device, a headset, a watch, etc.). Figure 1 A schematic diagram of an electronic device is exemplarily shown. Figure 1 The illustrated embodiment takes the electronic device 1000 as a mobile phone as an example.

[0044] Figure 2 The structural block diagram of an electronic device is shown as an example. Figure 2 As shown, the electronic device 1000 includes a processor 100 and a pressure sensor 200 electrically connected to the processor 100. When working, the pressure sensor 200 collects external pressure information and sends the pressure value of the external pressure to the processor 200 for the processor 100 to process.

[0045] Exemplarily, the electronic device 1000 may include a housing and a mainboard disposed inside the housing, the processor 100 and the pressure sensor 200 are both connected to the mainboard, and the electrical connection between the processor 100 and the pressure sensor 200 is achieved through the mainboard.

[0046] The pressure sensor 200 may be a micro-electro-mechanical system (MEMS), which is a new multidisciplinary sensor developed on the basis of microelectronics technology, and has the characteristics of small size, light weight, low power consumption, and easy integration. The pressure sensor 200 may be of four main types, namely, piezoresistive, capacitive, resonant, and piezoelectric. Among them, the piezoresistive pressure sensor has the characteristics of good stability, low manufacturing cost, and compatibility with COMS processes, and is widely used in the automotive field, industrial control field, consumer electronics field, construction field, and medical field.

[0047] The pressure sensor 200 can be used to measure gas pressure, liquid pressure, or contact pressure. The embodiment of the present disclosure is only described by taking the pressure sensor 200 for measuring gas pressure as an example.

[0048] Figure 3 A cross-sectional view of a pressure sensor is shown as an example. Figure 3 As shown, the pressure sensor 200 includes a pressure sensing chip 240 and a control chip 230. The pressure sensing chip 240 is configured to receive external pressure and generate an electrical signal corresponding to the external pressure. The control chip 230 is configured to determine the pressure value of the external pressure based on the electrical signal of the pressure sensing chip 240 and output the determined pressure value as an output value.

[0049] Continue to refer Figure 3 The pressure sensor 200 may further include a circuit board 210 , a protective cover 220 , a first connecting line 250 , and a second connecting line 260 .

[0050] The circuit board 210 is used to support and connect other components of the pressure sensor 200. Exemplarily, the control chip 230 is connected to one side of the circuit board 210, and the pressure sensing chip 240 is connected to the side of the control chip 230 away from the circuit board 210. In actual application, the circuit board 210 can be a printed circuit board 210 (Printed Circuit Board, PCB for short), and the pressure sensor 200 can be electrically connected to the external circuit through the circuit board 210. Exemplarily, the pressure sensing chip 240 is electrically connected to the control chip 230 through a first connecting line 250, and the control chip 230 is electrically connected to the circuit board 210 through a second connecting line 260. The circuit board 210 is provided with a metal pad structure, and the metal pad structure is soldered to the main board or the test system by reflow soldering to realize the electrical connection between the pressure sensor 200 and the main board or the test system.

[0051] The protective cover 220 is used to protect the pressure sensing chip 240, the control chip 230, the first connection line 250 and the second connection line 260 from external force collision, etc. Exemplarily, the protective cover 220 is buckled on one side of the circuit board 210, so that the protective cover 220 and the circuit board 210 form a receiving cavity, and the pressure sensing chip 240, the control chip 230, the first connection line 250 and the second connection line 260 are located in the receiving cavity. Exemplarily, the protective cover 220 is a metal cover.

[0052] The protective cover 220 is provided with a through hole 221, and the accommodating chamber is connected to the external environment through the through hole 221, so that the pressure inside and outside the accommodating chamber is equal. The pressure sensing chip 240 can infer the pressure outside the accommodating chamber by collecting the pressure inside the accommodating chamber.

[0053] Figure 4 is a cross-sectional view of a pressure sensor chip in the initial state in the related art. Figure 5 FIG. 1 is a cross-sectional view of a pressure sensor chip in the related art under external pressure. Figure 4 and Figure 5As shown, the pressure sensing chip in the related art includes a lower plate 101 and an upper plate 102 which are arranged relatively, and a cavity is formed between the lower plate 101 and the upper plate 102, and a piezoresistor 103 is arranged on the upper wall of the cavity. When the pressure sensing chip is subjected to external pressure, the upper wall of the cavity is deformed, driving the piezoresistor 103 to deform. After the piezoresistor 103 is deformed, the resistance value changes, that is, the voltage u across the piezoresistor 103 changes, so that the pressure value p of the external pressure can be calculated according to the voltage. For example, the functional relationship between the voltage u and the pressure value p is obtained, p=F(u) (usually F is a linear function, a quadratic function or a cubic function).

[0054] During the use of pressure sensor chips, due to the influence of the use environment, material internal stress, material creep and other properties, the curve of the functional relationship drifts, which leads to inaccurate output results of the pressure sensor chip. Therefore, the pressure sensor chip needs to be calibrated. However, since the pressure sensor chip has been assembled into a complete product, the pressure sensor chip needs to be removed from the complete product for calibration, which is inconvenient.

[0055] In view of this, an embodiment of the present disclosure provides a pressure sensor chip, which makes the calibration of the pressure sensor chip more convenient.

[0056] Figure 6 The cross-sectional view of a pressure sensor chip is shown as an example. Figure 6 As shown, the pressure sensing chip 240 includes an upper substrate 30, a lower substrate 10 and a piezoresistor 51. The upper substrate 30 and the lower substrate 10 are arranged opposite to each other, and the upper substrate 30 and the lower substrate 10 are made of conductive materials, and the upper substrate 30 and the lower substrate 10 are insulated. The upper substrate 30 includes a pressure-sensitive film, and a closed pressure-sensitive cavity 1 is provided between the pressure-sensitive film and the lower substrate 10. The piezoresistor 51 is connected to the pressure-sensitive film, and the piezoresistor 51 is insulated from the pressure-sensitive film. When the pressure-sensitive film is deformed, the resistance value of the piezoresistor 51 changes.

[0057] The pressure-sensitive film is used to deform when the pressure sensing chip 240 is subjected to external pressure, thereby causing the piezoresistor 51 connected to the pressure-sensitive film to deform. In order to make the pressure-sensitive film more easily deformable, thereby improving the sensitivity of the pressure sensing chip 240, the thickness of the pressure-sensitive film can be set thinner than the thickness of other parts of the upper substrate 30.

[0058] The pressure-sensitive film can be an integral structure with other structures of the upper substrate 30, and the pressure-sensitive film can also be connected to other structures of the upper substrate 30 through a connection process. Exemplarily, a groove 31 is provided on the side of the upper substrate 30 facing the lower substrate 10, and the bottom wall of the groove 31 serves as the pressure-sensitive film. Exemplarily, the upper substrate 30 includes a frame and a pressure-sensitive film, and the pressure-sensitive film is a film or a thin plate structure, which is connected to the frame through an adhesive or bonding process. In this case, the material of the pressure-sensitive film can be the same as or different from that of the frame.

[0059] The upper substrate 30 may include a pressure-sensitive film and a connecting portion arranged around the pressure-sensitive film, wherein the connecting portion is fixedly arranged, for example, the connecting portion is fixedly connected to the lower substrate 10. Since the pressure-sensitive film is a peripherally fixed structure, when the pressure-sensitive film is subjected to pressure, the deformation in the middle of the pressure-sensitive film is large and the deformation in the periphery is small, but the maximum deformation of the pressure-sensitive film is proportional to the average deformation of the pressure-sensitive film, that is, the larger the maximum deformation, the larger the average deformation. Here, in order to simplify the model, only the maximum deformation of the pressure-sensitive film under fixed pressure is evaluated. Taking a square pressure-sensitive film as an example, its maximum deformation is shown in the following formula (1).

[0060]

[0061] Wherein, P is the full-scale pressure of the pressure sensor 200, a is the side length of the pressure-sensitive membrane of the pressure sensor 200, μ is the Poisson's ratio of the material used in the pressure sensor 200, E is the elastic modulus of the material used in the pressure sensor 200, and h is the thickness of the pressure-sensitive membrane of the pressure sensor 200.

[0062] The pressure sensing chamber 1 may be a vacuum chamber, or may be filled with gas. When the pressure sensing chamber 1 is filled with gas, the pressure on the pressure sensing film is equal to the pressure difference between the inside and outside of the pressure sensing chamber 1 .

[0063] The materials of the upper substrate 30 and the lower substrate 10 may be the same or different. Exemplarily, both the upper substrate 30 and the lower substrate 10 are silicon substrates.

[0064] The piezoresistors 51 are connected to the pressure-sensitive film so as to deform along with the deformation of the pressure-sensitive film. Since the deformation near the center of the pressure-sensitive film is larger, the piezoresistors 51 can be arranged in the center of the pressure-sensitive film or near the center, thereby increasing the deformation of the piezoresistors 51 and further increasing the sensitivity of the pressure sensing chip 240. Of course, the piezoresistors 51 can also be arranged near the edge of the pressure-sensitive film, which is not limited in the embodiments of the present disclosure.

[0065] The varistor 51 can be connected and insulated with the pressure-sensitive film by various connection methods. For example, the varistor 51 can be bonded to the pressure-sensitive film by adhesive, and the adhesive is located between the varistor 51 and the pressure-sensitive film, so as to achieve connection and insulation between the varistor 51 and the pressure-sensitive film.

[0066] The number of the varistor 51 may be one or more. Figure 7 exemplarily shows a connection relationship diagram of multiple varistors 51. Figure 7 As shown, when there are multiple varistors 51 , the multiple varistors 51 can be connected to form a Wheatstone bridge.

[0067] Input voltage of the Wheatstone bridge:

[0068] V in =V in+ -V in-

[0069] The output voltage of the Wheatstone bridge is:

[0070] V out =V out+ -V out-

[0071] R1, R2, R3, and R4 represent the four arm resistors of the Wheatstone bridge, and Vout can be expressed by formula (2). In the process of preparing the sensitive chip, R1=R2=R3=R4=R. When external pressure acts on the sensitive chip, the resistors R1 and R3 decrease by ΔR, that is, their resistance values ​​become R-ΔR, and the resistors R2 and R4 increase by ΔR, that is, their resistance values ​​become R+ΔR, causing Vout to change. The change in Vout is proportional to the pressure value on the piezoresistive chip, as shown in formula (3), thereby converting the pressure signal into a voltage signal.

[0072]

[0073]

[0074] The upper substrate 30 and the lower substrate 10 are arranged oppositely and insulated, that is, the pressure-sensitive film and the lower substrate 10 are arranged oppositely and insulated. Since the pressure-sensitive film and the lower substrate 10 are both made of conductive materials, the pressure-sensitive film and the lower substrate 10 form an equivalent capacitor. When the pressure-sensitive film is deformed by the action of the force, the electrical parameters of the equivalent capacitor change, and as the deformation amount continues to change, the electrical parameters of the equivalent capacitor change continuously, that is, there is a corresponding relationship between the deformation amount of the pressure-sensitive film and the electrical parameters of the equivalent capacitor. Since there is a corresponding relationship between the deformation amount of the pressure-sensitive film and the magnitude of the force, there is a corresponding relationship between the magnitude of the force and the electrical parameters of the equivalent capacitor. When calibrating the pressure sensor chip 240, the magnitude of the force can be calculated by the electrical parameters of the equivalent capacitor, so as to calibrate the output value of the sensor chip, making the calibration of the sensor chip more convenient.

[0075] The electrical parameters of the equivalent capacitor may include the voltage across the equivalent capacitor, the capacitance value of the equivalent capacitor, etc.

[0076] The pressure sensing chip 240 may further include an upper electrode 61 and a lower electrode 62, wherein the upper electrode 61 is electrically connected to the upper substrate 30, and the lower electrode 62 is electrically connected to the lower substrate 10, thereby realizing electrical connection between the equivalent capacitor and the external circuit through the upper electrode 61 and the lower electrode 62. The upper electrode 61 and the lower electrode 62 may be located on the same side of the pressure sensing chip 240, thereby facilitating electrical connection between the pressure sensor 200 and the external circuit. For example, the upper electrode 61 and the lower electrode 62 may be located on a side of the upper substrate 30 away from the lower substrate 10. Of course, the upper electrode 61 and the lower electrode 62 may also be located on a side of the lower substrate 10 away from the upper substrate 30.

[0077] The upper substrate 30 may be provided with an overlap structure, which penetrates the upper substrate 30 in a direction perpendicular to the upper substrate 30, one end of the overlap structure is electrically connected to the lower electrode 62, and the other end of the overlap structure is electrically connected to the lower substrate 10, and the overlap structure is insulated from the upper substrate 30. The lower electrode 62 is electrically connected to the lower substrate 10 through the overlap structure, and the overlap structure is arranged inside the upper substrate 30, so that the structure of the pressure sensor chip 240 is more compact.

[0078] The upper substrate 30 may be provided with a via hole, which penetrates the upper substrate 30 in a direction perpendicular to the upper substrate 30, the overlap structure is arranged in the via hole, and a first insulating layer is arranged between the overlap structure and the inner wall of the via hole. The first insulating layer can prevent the overlap structure from contacting the upper substrate 30, thereby achieving insulation between the overlap structure and the upper substrate 30.

[0079] A second insulating layer 40 may be provided on the side of the upper substrate 30 away from the lower substrate 10 , and the upper electrode 61 , the lower electrode 62 and the varistor circuit are connected on the side of the second insulating layer 40 away from the lower substrate 10 , thereby achieving insulation between the lower electrode 62 , the varistor 51 and the upper substrate 30 .

[0080] The side of the lower substrate 10 facing the upper substrate 30 is oxidized to form the third insulating layer 20, and the upper substrate 30 is bonded to the third insulating layer 20. Alternatively, the side of the upper substrate 30 facing the lower substrate 10 is oxidized to form the third insulating layer 20, and the lower substrate 10 is bonded to the third insulating layer 20.

[0081] Exemplarily, both the upper substrate 30 and the lower substrate 10 are silicon substrates, the side of the lower substrate 10 facing the upper substrate 30 is oxidized to form a silicon oxide film, and the upper substrate 30 is bonded to the silicon oxide film to achieve the connection between the upper substrate 30 and the lower substrate 10. Alternatively, the side of the upper substrate 30 facing the lower substrate 10 is oxidized to form a silicon oxide film, and the lower substrate 10 is bonded to the silicon oxide film to achieve the connection between the upper substrate 30 and the lower substrate 10.

[0082] Figures 8 to 13 The following diagram exemplarily shows a process diagram of manufacturing a pressure sensor chip 240. Figures 8 to 13As shown, a preparation process of a pressure sensor chip 240 includes the following steps.

[0083] a. Provide a first substrate.

[0084] The first substrate includes an upper substrate 30, a second insulating layer 40 and a semiconductor layer 50 which are stacked in sequence. Exemplarily, the first substrate is a SOI material, wherein the resistivity of the upper substrate 30 is ≤0.001Ω.

[0085] b. Form a varistor 51 on the first substrate.

[0086] For example, the semiconductor layer 50 may be subjected to photolithography and etching to form the varistor 51 .

[0087] c. Forming a groove 31 on the first substrate.

[0088] For example, the upper substrate 30 is subjected to photolithography and etching to form a groove 31 on the upper substrate 30 , and the bottom wall of the groove 31 is a pressure-sensitive film.

[0089] d. Provide a second substrate.

[0090] The second substrate may be a silicon substrate, and a third insulating layer 20 is disposed on a surface of one side of the silicon substrate. For example, the surface of the silicon substrate is oxidized to form a silicon oxide film.

[0091] e. Connect the first substrate and the second substrate.

[0092] The first substrate and the second substrate can be adhered or bonded. For example, the upper substrate 30 is a silicon substrate, the third insulating layer 20 is a silicon oxide film, and the upper substrate 30 and the third insulating layer 20 can be bonded to achieve the connection between the first substrate and the second substrate.

[0093] After the first substrate and the second substrate are connected, the groove 31 and the second substrate form a pressure sensing cavity 1 .

[0094] f. Etching to form the first via hole 2 and the second via hole 3.

[0095] The first via hole 2 penetrates the second insulating layer 40, so that part of the structure of the upper substrate 30 is exposed through the first via hole 2. The second via hole 3 penetrates the second insulating layer 40, the upper substrate 30 and the third insulating layer 20, so that part of the structure of the lower substrate 10 is exposed through the second via hole 3.

[0096] g. Form an overlapping structure.

[0097] For example, metal material is filled in the first via hole 2 and the second via hole 3 by PVD, CVD or electroplating, so as to form the first overlapping structure 71 and the second overlapping structure 72 .

[0098] h. Form an upper electrode 61 and a lower electrode 62.

[0099] For example, the upper electrode 61 is formed at the position corresponding to the first overlap structure 71 by using the lift-off process, and the lower electrode 62 is formed at the position corresponding to the second overlap structure 72. In practical applications, a resistor electrode 63 electrically connected to the varistor 51 can also be formed at the position corresponding to the varistor electrode.

[0100] The embodiment of the present disclosure also provides a pressure sensor calibration method for calibrating the above-mentioned pressure sensor. Fig.14 The following is a flowchart showing a method for calibrating a pressure sensor. Fig.14 As shown, the pressure sensor calibration method includes the following steps.

[0101] Step S100: Acquire the test output value of the pressure sensor.

[0102] When the pressure sensing chip in the pressure sensor is subjected to force, the pressure-sensitive film is deformed, thereby changing the resistance value of the varistor. When the resistance value of the varistor changes, the electrical signal of the varistor changes (for example, the voltage across the varistor and the current flowing through the varistor change). The control chip can calculate the pressure value of the external force based on the electrical signal of the varistor and output it as an output value.

[0103] During calibration, applying force to the pressure-sensitive film may cause the pressure-sensitive film to deform. At this time, the deformation of the pressure-sensitive film is called a test deformation. When the pressure-sensitive film is subjected to the test deformation, the output value of the pressure sensor is called a test output value.

[0104] For example, the pressure sensor is electrically connected to the test system, and the test output value of the pressure sensor is read through the test system.

[0105] The force applied to the pressure-sensitive film may be a force inside the pressure sensor chip, such as applying voltage to the upper substrate and the lower substrate, and the charges accumulated in the upper substrate and the lower substrate are opposite in electrical properties, so that the pressure-sensitive film deforms toward the lower substrate under the action of the electrostatic force. Of course, the force may also be a force outside the pressure sensor chip, such as increasing the air pressure of the environment where the pressure sensor chip is located, or directly applying contact pressure on the pressure-sensitive film.

[0106] Step S200: Obtain the theoretical output value of the pressure sensor.

[0107] A mapping relationship is preset inside the pressure sensor. For example, a memory is provided in the control chip, and the mapping relationship is stored in the memory.

[0108] The mapping relationship includes the mapping relationship between the deformation of the pressure-sensitive film and the theoretical output value of the pressure sensor. For example, after the pressure sensor is prepared, different forces are applied to the pressure sensor chip using a standard high-precision pressure calibration device, and the output values ​​of the pressure sensor are read respectively, thereby generating a mapping relationship between the force and the theoretical output value; different voltages are applied to the upper substrate and the lower substrate, and the output values ​​of the pressure sensor are read respectively, thereby generating a mapping relationship between the voltage and the theoretical output value. The mapping relationship between the deformation and the force can be calculated by formula (1), so the mapping relationship between the deformation and the theoretical output value of the pressure sensor can be obtained.

[0109] According to the mapping relationship, a theoretical output value corresponding to the test deformation amount can be obtained. The mapping relationship can be a table or a function relationship, which is not limited in the embodiment of the present disclosure.

[0110] Step S300: Compensating the output value of the pressure sensor according to the test output value and the theoretical output value.

[0111] When the difference between the test output value and the theoretical output value is small, the error of the pressure sensor is small and the output value does not need to be compensated. When the difference between the test output value and the theoretical output value is large, the output value of the pressure sensor needs to be compensated.

[0112] There are many ways to compensate. The difference between the test output value and the theoretical output value can be added to the output value of the pressure sensor, or the theoretical output value can be used as the output value of the pressure sensor.

[0113] In the calibration method of the pressure sensor provided by the embodiment of the present disclosure, the upper substrate and the lower substrate are arranged relative to each other and insulated, that is, the pressure-sensitive film and the lower substrate are arranged relative to each other and insulated. Since the pressure-sensitive film and the lower substrate are both made of conductive materials, the pressure-sensitive film and the lower substrate form an equivalent capacitor. When the pressure-sensitive film is deformed by the action of the force, the electrical parameters of the equivalent capacitor change, and as the deformation amount continues to change, the electrical parameters of the equivalent capacitor change continuously, that is, there is a corresponding relationship between the deformation amount of the pressure-sensitive film and the electrical parameters of the equivalent capacitor. Since there is a corresponding relationship between the deformation amount of the pressure-sensitive film and the magnitude of the force, there is a corresponding relationship between the magnitude of the force and the electrical parameters of the equivalent capacitor. When calibrating the pressure sensor chip, the magnitude of the force can be calculated by the electrical parameters of the equivalent capacitor, so as to calibrate the output value of the sensor chip, making the calibration of the sensor chip more convenient.

[0114] Optionally, obtaining the test output value of the pressure sensor in step S100 may include:

[0115] S110: applying a test voltage to the upper substrate and the lower substrate.

[0116] The deformation of the pressure-sensitive film under the action of the test voltage is called the test deformation.

[0117] S120: Obtain the output value of the pressure sensor as a test output value.

[0118] For example, the output value of the pressure sensor when the test voltage is applied to the upper substrate and the lower substrate is read by the test system.

[0119] For example, the preset mapping relationship may include a mapping relationship between the voltage between the upper substrate and the lower substrate and the theoretical output value, so as to determine the theoretical output value corresponding to the test voltage according to the mapping relationship, and then compensate the output value of the pressure sensor according to the test output value and the theoretical output value.

[0120] When voltage is applied to the upper substrate and the lower substrate, the pressure-sensitive film is not subjected to external force, thereby preventing the external force from being applied to the pressure-sensitive film and affecting the accuracy of calibration.

[0121] Optionally, obtaining a theoretical output value of the pressure sensor in step S200 includes:

[0122] Step S210: Obtain a test capacitance value.

[0123] The upper substrate and the lower substrate are arranged opposite to each other and insulated, so that the upper substrate and the lower substrate form an equivalent capacitor. When the pressure-sensitive film is deformed, the distance between the pressure-sensitive film and the lower substrate changes, thereby changing the capacitance value of the equivalent capacitor. During calibration, the deformation of the pressure-sensitive film is the test deformation, and the capacitance value of the equivalent capacitor when the pressure-sensitive film is tested is the test capacitance value.

[0124] Step S220: determining a theoretical output value corresponding to the test capacitance value according to the mapping relationship.

[0125] The mapping relationship may include a mapping relationship between a capacitance value and a theoretical output value. For example, after the pressure sensor is manufactured, a standard high-precision pressure calibration device is used to apply different forces to the pressure sensor chip, and the output value of the pressure sensor and the capacitance value of the equivalent capacitor are read respectively, thereby generating a mapping relationship between the capacitance value and the theoretical output value.

[0126] According to the mapping relationship, a theoretical output value corresponding to the test capacitance value can be obtained. The mapping relationship can be a table or a function relationship, which is not limited in the embodiment of the present disclosure.

[0127] When the pressure sensor is calibrated through the capacitance value, the pressure-sensitive film of the pressure sensor chip may be subjected to external force or not, which has lower requirements on the calibration environment and is more convenient.

[0128] The above is only a specific embodiment of the present disclosure, but the protection scope of the present disclosure is not limited thereto. Any person skilled in the art who is familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed in the present disclosure, which should be included in the protection scope of the present disclosure. Therefore, the protection scope of the present disclosure should be based on the protection scope of the claims.

Claims

1. A pressure sensor chip, characterized in that: It includes an upper substrate, a lower substrate and a varistor; The upper substrate and the lower substrate are arranged opposite to each other, the upper substrate and the lower substrate are made of conductive materials, and the upper substrate and the lower substrate are insulated from each other; The upper substrate comprises a pressure-sensitive film, and a closed pressure-sensitive cavity is provided between the pressure-sensitive film and the lower substrate; The varistor is connected to the pressure-sensitive film, and the varistor is insulated from the pressure-sensitive film. When the pressure-sensitive film is deformed, the resistance value of the varistor changes.

2. The pressure sensor chip according to claim 1, characterized in that The pressure sensing chip further includes an upper electrode and a lower electrode, wherein the upper electrode is electrically connected to the upper substrate, and the lower electrode is electrically connected to the lower substrate, and the upper electrode and the lower electrode are located on a side of the upper substrate away from the lower substrate.

3. The pressure sensor chip according to claim 2, characterized in that A second overlap structure is provided in the upper substrate, and the second overlap structure penetrates the upper substrate in a direction perpendicular to the upper substrate, one end of the second overlap structure is electrically connected to the lower electrode, and the other end of the second overlap structure is electrically connected to the lower substrate, and the overlap structure is insulated from the upper substrate.

4. The pressure sensor chip according to claim 4, characterized in that The upper substrate is provided with a second via hole, the second via hole penetrates the upper substrate in a direction perpendicular to the upper substrate, the second overlapping structure is arranged in the second via hole, and a first insulating layer is provided between the second overlapping structure and the inner wall of the second via hole.

5. The pressure sensor chip according to claim 2, characterized in that A second insulating layer is provided on a side of the upper substrate away from the lower substrate, and the upper electrode, the lower electrode and the varistor are connected on a side of the second insulating layer away from the lower substrate.

6. The pressure sensor chip according to claim 1, characterized in that ,, the pressure sensing chip includes a plurality of the piezoresistors, and the plurality of the piezoresistors are connected to form a Wheatstone bridge.

7. The pressure sensor chip according to claim 1, characterized in that ,, the lower substrate is oxidized on a side facing the upper substrate to form the third insulating layer, and the upper substrate and the third insulating layer are bonded; or, the upper substrate is oxidized on a side facing the lower substrate to form the third insulating layer, and the lower substrate and the third insulating layer are bonded.

8. A pressure sensor, characterized in that: It comprises a control chip and a pressure sensing chip as claimed in any one of claims 1 to 7, wherein the piezoresistor, the upper substrate and the lower substrate of the pressure sensing chip are electrically connected to the control chip.

9. A pressure sensor calibration method, used for calibrating the pressure sensor according to claim 8, characterized in that: The calibration method comprises: Acquire a test output value of the pressure sensor; the test output value is: the output value of the pressure sensor when the pressure-sensitive film undergoes a test deformation amount; Acquire a theoretical output value of the pressure sensor; the theoretical output value is: an output value corresponding to the test deformation amount in a preset mapping relationship of the pressure sensor; The output value of the pressure sensor is compensated according to the test output value and the theoretical output value.

10. The pressure sensor calibration method according to claim 9, characterized in that: The obtaining of the test output value of the pressure sensor comprises: A test voltage is applied to the upper substrate and the lower substrate; the pressure-sensitive film undergoes the test deformation amount under the action of the test voltage; An output value of the pressure sensor is obtained as a test output value.

11. The pressure sensor calibration method according to claim 10, characterized in that: When acquiring the test output value, the pressure-sensitive film is not subjected to external force.

12. The pressure sensor calibration method according to claim 9, characterized in that: The obtaining of the theoretical output value of the pressure sensor comprises: Acquire a test capacitance value; the test capacitance value is a capacitance value between the upper substrate and the lower substrate when the pressure-sensitive film undergoes the test deformation amount; A theoretical output value corresponding to the test capacitance value is determined according to the mapping relationship.

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