CN114689225A - Absolute pressure type MEMS piezoresistive sensor and self-testing method thereof - Google Patents
Absolute pressure type MEMS piezoresistive sensor and self-testing method thereof Download PDFInfo
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- G01L1/00—Measuring force or stress, in general
- G01L1/20—Measuring force or stress, in general by measuring variations in ohmic resistance of solid materials or of electrically-conductive fluids; by making use of electrokinetic cells, i.e. liquid-containing cells wherein an electrical potential is produced or varied upon the application of stress
- G01L1/22—Measuring force or stress, in general by measuring variations in ohmic resistance of solid materials or of electrically-conductive fluids; by making use of electrokinetic cells, i.e. liquid-containing cells wherein an electrical potential is produced or varied upon the application of stress using resistance strain gauges
- G01L1/2287—Measuring force or stress, in general by measuring variations in ohmic resistance of solid materials or of electrically-conductive fluids; by making use of electrokinetic cells, i.e. liquid-containing cells wherein an electrical potential is produced or varied upon the application of stress using resistance strain gauges constructional details of the strain gauges
- G01L1/2293—Measuring force or stress, in general by measuring variations in ohmic resistance of solid materials or of electrically-conductive fluids; by making use of electrokinetic cells, i.e. liquid-containing cells wherein an electrical potential is produced or varied upon the application of stress using resistance strain gauges constructional details of the strain gauges of the semi-conductor type
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- G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
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- G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
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- G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
- G01L9/00—Measuring steady of quasi-steady pressure of fluid or fluent solid material by electric or magnetic pressure-sensitive elements; Transmitting or indicating the displacement of mechanical pressure-sensitive elements, used to measure the steady or quasi-steady pressure of a fluid or fluent solid material, by electric or magnetic means
- G01L9/02—Measuring steady of quasi-steady pressure of fluid or fluent solid material by electric or magnetic pressure-sensitive elements; Transmitting or indicating the displacement of mechanical pressure-sensitive elements, used to measure the steady or quasi-steady pressure of a fluid or fluent solid material, by electric or magnetic means by making use of variations in ohmic resistance, e.g. of potentiometers, electric circuits therefor, e.g. bridges, amplifiers or signal conditioning
- G01L9/04—Measuring steady of quasi-steady pressure of fluid or fluent solid material by electric or magnetic pressure-sensitive elements; Transmitting or indicating the displacement of mechanical pressure-sensitive elements, used to measure the steady or quasi-steady pressure of a fluid or fluent solid material, by electric or magnetic means by making use of variations in ohmic resistance, e.g. of potentiometers, electric circuits therefor, e.g. bridges, amplifiers or signal conditioning of resistance-strain gauges
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Abstract
The invention relates to the technical field of piezoresistive sensors, in particular to an absolute pressure type MEMS piezoresistive sensor and a self-testing method thereof. In the sensor, the metal lead module is arranged on one side of the protective layer, which is far away from the thin film layer; the first magnetic field generating device and the second magnetic field generating device are arranged around the piezoresistive sensing module; the signal input end of the signal processing circuit is connected with the signal output end of the piezoresistive sensing module; the signal processing circuit is respectively connected with the metal wire module and the piezoresistive sensing module in a power supply mode. The invention provides the pressure self-testing function of the absolute pressure type MEMS piezoresistive sensor, saves the processes of building off-chip testing equipment and repeatedly disassembling and testing, and improves the detection efficiency of the absolute pressure type MEMS piezoresistive sensor.
Description
Technical Field
The invention relates to the technical field of piezoresistive sensors, in particular to an absolute pressure type MEMS piezoresistive sensor and a self-testing method thereof.
Background
The MEMS (Micro Electro Mechanical System) technology is developed by combining with other processing technologies on the basis of the microelectronic manufacturing process, and is frequently applied to the high-tech field requiring small size, high precision, high reliability and low power consumption.
The pressure-insulating MEMS piezoresistive sensor belongs to a piezoresistive sensor, can realize the measurement of the pressure, the strain and the like of the outside by utilizing the piezoresistive effect of a semiconductor material, converts the outside pressure value into an electric signal to be output, and is widely applied to control systems in the fields of water conservancy and hydropower, railway traffic, aerospace, petrochemical industry, electric power, ship industry and the like.
The absolute pressure type MEMS piezoresistive sensor needs to be regularly detected after being put into use, complex physical excitation is carried out on the absolute pressure type MEMS piezoresistive sensor by high-precision off-chip testing equipment generally, but the existing off-chip testing equipment is large and expensive testing equipment generally, so that the cost of the whole testing process is high, time and labor are wasted, and the efficiency is not high.
Therefore, how to improve the detection efficiency of the absolute pressure type MEMS piezoresistive sensor is a technical problem that needs to be solved at present.
Disclosure of Invention
The invention aims to provide an absolute pressure type MEMS piezoresistive sensor and a self-testing method thereof, so that the detection efficiency of the absolute pressure type MEMS piezoresistive sensor is improved.
In order to achieve the above object, the embodiments of the present invention provide the following solutions:
in a first aspect, an embodiment of the present invention provides an absolute pressure type MEMS piezoresistive sensor, including: the piezoresistive sensing module comprises a metal lead module, a piezoresistive sensing module, a first magnetic field generating device, a second magnetic field generating device and a signal processing circuit;
the piezoresistive sensing module comprises: the protective layer, the film layer, the silicon substrate layer and the glass layer are stacked; a cavity structure is arranged in the silicon substrate layer; one side of the thin film layer, which is close to the protective layer, is provided with a piezoresistive strip; a metal electrode is arranged on one side of the protective layer, which is far away from the thin film layer; the metal electrode is electrically connected with the piezoresistive strip;
the metal lead module is arranged on one side of the protective layer, which is far away from the thin film layer;
the first magnetic field generating device and the second magnetic field generating device are arranged around the piezoresistive sensing module to jointly provide a static magnetic field for the piezoresistive sensing module;
the signal input end of the signal processing circuit is connected with the signal output end of the piezoresistive sensing module; and the signal processing circuit is respectively connected with the metal wire module and the piezoresistive sensing module in a power supply manner.
In one possible embodiment, the metal wire module comprises: the device comprises a first strip-shaped metal electrode, a second strip-shaped metal electrode and at least two metal wires;
the at least two metal wires are connected in parallel between the first strip-shaped metal electrode and the second strip-shaped metal electrode;
the signal processing circuit is electrically connected with the first strip-shaped metal electrode; the second strip-shaped metal electrode is grounded.
In a possible embodiment, the at least two metal wires are each arranged parallel to the protective layer.
In one possible embodiment, the metal wire has a rectangular cross-sectional shape.
In a possible embodiment, the ratio of the length to the cross-sectional area of the metal wire is greater than a predetermined value.
In a possible embodiment, the first magnetic field generating device is a first solenoid and the second magnetic field generating device is a second solenoid;
the first magnetic field generating device and the second magnetic field generating device are both arranged on one side, far away from the silicon substrate layer, of the glass layer; wherein the polarities of the magnetic poles of the first magnetic field generating device and the second magnetic field generating device on the side close to the glass layer are opposite;
the signal processing circuit is electrically connected with the first solenoid and the second solenoid respectively.
In a possible embodiment, the first magnetic field generating device is a first single magnet, and the second magnetic field generating device is a second single magnet.
In one possible embodiment, the first magnetic field generating device is a first magnetic pole of a U-shaped magnet, and the second magnetic field generating device is a second magnetic pole of the U-shaped magnet.
In one possible embodiment, the signal processing circuit comprises a processor, a controllable switch, a digital-to-analog converter, an analog-to-digital converter, a temperature compensation circuit, and a differential amplifier;
the power supply output end of the processor is connected with the first switch input end of the controllable switch through the digital-to-analog converter; the control end of the processor is connected with the switch control end of the controllable switch;
the first switch output end of the controllable switch is grounded through the metal lead module;
a second switch output of the controllable switch is grounded through the first solenoid; a third switch output of the controllable switch is connected to ground through the second solenoid;
the fourth switch output end of the controllable switch is connected with the first bridge input end of the Wheatstone bridge; a second bridge input of the Wheatstone bridge is grounded; a first bridge output end of the Wheatstone bridge is connected with a first input end of the differential amplifier through the temperature compensation circuit; a second bridge output end of the Wheatstone bridge is connected with a second input end of the differential amplifier; the output end of the differential amplifier is connected with the signal input end of the processor through the analog-to-digital converter; wherein the Wheatstone bridge is formed by connecting the piezoresistive strips.
In a second aspect, an embodiment of the present invention provides a self-testing method for an absolute pressure MEMS piezoresistive sensor according to any one of the first aspects, where the method includes:
supplying power to the metal lead module by at least two groups of set voltages so as to enable the metal lead module to generate at least two groups of ampere forces towards the piezoresistive sensing module;
acquiring at least two groups of pressure sensing signals output by the piezoresistive sensing module under the at least two groups of ampere forces; the pressure sensing signal is a voltage value representing the resistance variation of the piezoresistive sensing module;
and calculating the sensitivity and the linearity of the piezoresistive sensing module according to the at least two groups of pressure sensing signals.
Compared with the prior art, the invention has the following advantages and beneficial effects:
according to the invention, the metal lead module is arranged on one side of the piezoresistive sensing module, and the first magnetic field generating device and the second magnetic field generating device which are arranged near the piezoresistive sensing module can form a static magnetic field near the piezoresistive sensing module, so that ampere force towards the piezoresistive sensing module can be generated in the static magnetic field after the metal lead module is conductive, the absolute pressure type MEMS piezoresistive sensor can carry out pressure self-test according to the ampere force, the processes of building off-chip test equipment and repeatedly disassembling the test are omitted, the detection efficiency of the absolute pressure type MEMS piezoresistive sensor is improved, the sensor can realize functional self-test while not depending on the traditional test equipment, and meanwhile, after the sensor is put into use for a period of time, the performance of the sensor can still be tested on the basis of not disassembling the sensor.
Drawings
In order to more clearly illustrate the embodiments of the present specification or the technical solutions in the prior art, the drawings needed to be used in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present specification, and it is obvious for those skilled in the art that other drawings can be obtained according to the drawings without creative efforts.
Fig. 1 is a schematic structural diagram of an absolute pressure type MEMS piezoresistive sensor according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of an arc-shaped static magnetic field distribution provided by an embodiment of the present invention;
fig. 3 is a schematic structural diagram of a metal wire module according to an embodiment of the present invention;
FIG. 4 is a schematic diagram of a signal processing circuit according to an embodiment of the present invention;
FIG. 5 is a flow chart of a method for self-testing an absolute pressure MEMS piezoresistive sensor according to an embodiment of the present invention.
Description of reference numerals: the sensor module comprises a metal lead module 1, a piezoresistive sensing module 2, a protective layer 21, a thin film layer 22, a piezoresistive strip 221, a metal electrode 222, a silicon substrate layer 23, a cavity structure 231, a glass layer 24, a first magnetic field generating device 31, a second magnetic field generating device 32, a signal processing circuit 4, a processor 41, a controllable switch 42, a digital-to-analog converter 43, an analog-to-digital converter 44, a temperature compensation circuit 45 and a differential amplifier 46.
Detailed Description
In the following, the technical solutions in the embodiments of the present invention will be clearly and completely described with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments, and all other embodiments obtained by a person skilled in the art based on the embodiments of the present invention belong to the protection scope of the embodiments of the present invention.
Referring to fig. 1, fig. 1 is a schematic structural diagram of an embodiment of the structure, which specifically includes: the sensor comprises a metal lead module 1, a piezoresistive sensing module 2, a first magnetic field generating device 31, a second magnetic field generating device 32 and a signal processing circuit 4.
Specifically, a silicon nitride material may be used to make the protection layer 21, and the thin film layer 22 and the silicon substrate layer 23 may be silicon wafers of the same material, or of course, a deep silicon etching process may be adopted to form the cavity structure 231 on one side of the silicon substrate material, and the thin film layer 22 is correspondingly formed on the other side of the silicon substrate material. The glass layer 24 and the silicon substrate layer 23 can be connected by a bonding process.
The movable film layer 22 is arranged on the cavity structure 231 in the pressure-insulating type MEMS piezoresistive sensor, the surface of the film layer 22 forms the piezoresistive strips 221 through an ion implantation technology, then the bottom of the silicon substrate layer 23 is bonded with glass to form a vacuum-sealed cavity, when the top end of the film is applied with pressure from the outside, due to ion implantation, the piezoresistive effect of the piezoresistive strips 221 on the surface of the film layer 22 is amplified, the resistivity of the piezoresistive strips 221 changes, the four piezoresistive strips 221 communicated with the surface of the film form a Wheatstone bridge, the pressure value borne by the surface of the film can be calculated by measuring the output voltage value of the bridge, and the purpose of measuring absolute pressure is achieved.
The process of calculating the pressure-sensitive signal of the pressure-insulated MEMS piezoresistive sensor in the following embodiment is briefly described here. The piezoresistive sensing module 2 in this embodiment is mainly used for pressure detection based on the piezoresistive effect of the material. The piezoresistive effect is a physical effect that, for a metal or a semiconductor material, if pressure or tension is applied along a certain crystal plane of the metal or the semiconductor material, the volume of the semiconductor changes, the inside of a crystal lattice of the semiconductor is distorted, an energy band changes, the mobility and the concentration of majority carriers in a conduction band change, and the resistivity changes significantly.
The change in resistivity (Δ ρ/ρ) can be expressed as the product of the piezoresistive coefficient and the stress experienced, and is given by the formula:
wherein, pilIs the longitudinal piezoresistive coefficient, pitIs the transverse piezoresistive coefficient, σlFor longitudinal stress, σtIs a transverse stress.
Piezoresistive material (i.e. piezoresistive strip 221) placed along axis <100>, its specific piezoresistive coefficient is:
πl,＜100>＝π11,πt,＜100>＝π12。
the piezoresistive material (i.e., piezoresistive strip 221) is placed along axis <110> with specific piezoresistive coefficients:
and the change amount (dR/R) of the resistance value of the material is as follows:
wherein, the first and the second end of the pipe are connected with each other,
the resistance value of the piezoresistive material is changed due to the size change factor,
is the resistance value change of the piezoresistive material caused by piezoresistive effect.
Because the temperature change is not large and the size change of the piezoresistive material is very weak in the process of the resistance value change of the piezoresistive material caused by the piezoresistive effect, the resistance value change of the material caused by the piezoresistive effect is much larger than the resistance value change caused by the geometric size change, and therefore, if the size change factor of the material is not considered, the resistance change quantity can be expressed by the following formula:
after the resistance variable quantity is obtained, the external pressure can be represented, and absolute pressure detection is realized.
The first magnetic field generator 31 and the second magnetic field generator 32 are disposed around the piezoresistive sensing module 2 to jointly provide a static magnetic field for the piezoresistive sensing module 2.
Specifically, the first magnetic field generating device 31 and the second magnetic field generating device 32 are both arranged on one side of the glass layer 24 away from the silicon substrate layer 23; wherein, the polarities of the magnetic poles at the side close to the glass layer 24 of the first magnetic field generating device 31 and the second magnetic field generating device 32 are opposite, so as to form an arc-shaped static magnetic field around the piezoresistive sensing module 2.
Specifically, the first magnetic field generating device 31 and the second magnetic field generating device 32 can form an arc-shaped static magnetic field distribution near the piezoresistive sensing module 2 because the magnetic induction lines at the magnetic poles close to the glass layer 24 are perpendicular to the glass layer 24, and the polarities of the two magnetic poles are opposite, as shown in fig. 2, the first magnetic field generating device 31 and the second magnetic field generating device 32 are a schematic diagram of the arc-shaped static magnetic field distribution provided in this embodiment.
Specifically, the first magnetic field generating device 31 is a first single magnet, and the second magnetic field generating device 32 is a second single magnet, where the single magnet may be a cylindrical button magnet or a bar magnet; the first magnetic field generator 31 may be a first magnetic pole of a U-shaped magnet, and the second magnetic field generator 32 may be a second magnetic pole of the U-shaped magnet.
Of course, the first magnetic field generating device 31 may also be a first solenoid, and the second magnetic field generating device 32 may also be a second solenoid. The signal processing circuit 4 supplies electric power to the first solenoid and the second solenoid so that both ends of the first solenoid and the second solenoid form magnetic poles, respectively.
The metal conducting wire module 1 is arranged on one side, far away from the thin film layer 22, of the protective layer 21, the signal processing circuit 4 is in power supply connection with the metal conducting wire module 1, due to the existence of a magnetic field near the piezoresistive sensing module 2, after the metal conducting wire module 1 is electrified, the metal conducting wire can generate ampere force towards the piezoresistive sensing module 2, and due to the fact that the ampere force is related to the electrifying current in the metal conducting wire, controllable pressure can be applied to the piezoresistive sensing module 2 through the metal conducting wire module 1 in the embodiment, and therefore pressure self-testing of the absolute pressure type MEMS piezoresistive sensor can be conducted.
In order to make the ampere force generated by the metal wire module 1 act on the piezoresistive sensing module 2 uniformly, this embodiment further provides a structure of the metal wire module 1, as shown in fig. 3, which is a schematic structural diagram of the metal wire module 1, and the metal wire module 1 is disposed in the middle of a wheatstone bridge composed of 4 piezoresistive strips 221, and specifically includes: a first strip-shaped metal electrode 222, a second strip-shaped metal electrode 222 and a plurality of (at least two) metal wires, wherein the metal wires are uniformly connected in parallel between the first strip-shaped metal electrode 222 and the second strip-shaped metal electrode 222; the signal processing circuit 4 is electrically connected with the first strip-shaped metal electrode 222; the second strip-shaped metal electrode 222 is grounded. Therefore, after the signal processing circuit 4 supplies power, because the intervals of the metal wires are the same, the currents in the metal wires are the same, all the metal wires can generate ampere force towards the piezoresistive sensing module 2, the reliability of the test is ensured, and the precision of the test is improved.
Specifically, the metal wires may be gold wires, silver wires, aluminum wires, or the like capable of generating an ampere force in a magnetic field, and may be added above the protective layer by a photolithography process.
Of course, in order to further enable the ampere force generated by the metal wire module 1 to act on the piezoresistive sensing module 2 more uniformly, the cross-sectional shapes of the metal wires are all rectangles with the same size, and the rectangular wires can act the ampere force on the piezoresistive sensing module 2 more stably than the round wires.
Since the metal wire module 1 generates heat when generating an ampere force, the heat can affect the size of the piezoresistive strip 221, thereby affecting the accuracy of the absolute pressure MEMS piezoresistive sensor.
In the present embodiment, the ratio of the length to the cross-sectional area of each metal wire is greater than a predetermined value, i.e., the metal wire module 1 is formed by selecting wires with the longest length and the smallest cross-sectional area, so as to reduce the heat generation amount of the metal wire module 1 as much as possible.
See in particular the following formula:
the power generated by the energization on a single metal wire is calculated as follows:
wherein, R represents the resistance of a single metal wire and has the unit of ohm (omega); a represents the width of the section of a single metal wire, and the unit is meter (m); b represents the height of the section of the single metal wire, and the unit is meter (m); ρ represents the resistivity of the metal wire in ohm-meters (Ω · m); p represents the power generated by electrifying on a single metal wire, and the unit is watt (W); v represents the self-test voltage input by the CPU into the metal conductor module 1 in volts (V).
It can be seen that the length of a single metal wire is as large as possible, the sectional area of the metal wire is as small as possible, the self-test voltage is as small as possible, and the applied magnetic field is as large as possible, so that the whole metal wire module 1 structure can generate as much ampere force as possible and generate as little heat as possible.
The signal processing circuit 4 comprises a processor 41, a controllable switch 42, a digital-to-analog converter 43, an analog-to-digital converter 44, a temperature compensation circuit 45 and a differential amplifier 46.
As shown in fig. 4, which is a connection schematic diagram of the signal processing circuit 4 provided in this embodiment, specifically, a power supply output end of the processor 41 is connected to a first switch input end of the controllable switch 42 through the digital-to-analog converter 43; the control end of the processor 41 is connected with the switch control end of the controllable switch 42; the first switch output end of the controllable switch 42 is grounded through the metal lead module 1; the second switch output of the controllable switch 42 is connected to ground through the first solenoid; the third switch output of the controllable switch 42 is connected to ground through the second solenoid; the fourth switch output of the controllable switch 42 is connected to the first bridge input of the wheatstone bridge; the second bridge input end of the Wheatstone bridge is grounded; a first bridge output terminal of the wheatstone bridge is connected to a first input terminal of a differential amplifier 46 through a temperature compensation circuit 45; a second bridge output of the wheatstone bridge is connected to a second input of the differential amplifier 46; the output end of the differential amplifier 46 is connected with the signal input end of the processor 41 through the analog-to-digital converter 44; wherein the wheatstone bridge is formed by connecting piezoresistive strips 221.
Specifically, the processor 41 may be a single chip, an MCU chip, or the like, and the temperature compensation circuit 45 may be a parallel circuit of a thermistor and a resistor with a small temperature coefficient, which is not limited herein.
Because the signal processing circuit 4 uses fewer elements and the number of switches is reduced by using the one-in-one-out controllable switch 42, the signal processing circuit 4 can be manufactured into a small-sized PCB, so that the metal lead module 1, the piezoresistive sensing module 2, the first magnetic field generating device 31, the second magnetic field generating device 32 and the signal processing circuit 4 can be tightly packaged to form an isolated MEMS piezoresistive sensor with a pressure self-test function.
The working principle of the embodiment is as follows:
in the embodiment, a metal wire module 1 is additionally arranged on a sensitive film of a piezoresistive sensing module 2 through an MEMS (micro-electromechanical systems) processing technology. When the whole piezoresistive sensing module 2 is in a magnetic field and the metal conducting wire module 1 is electrified, a downward ampere force is generated on the metal conducting wire module 1 under the action of the magnetic field, a sensitive film of the piezoresistive sensing module 2 deforms under the action of the ampere force, so that the resistance value of the piezoresistor changes, the piezoresistive sensing module 2 outputs a voltage signal representing the resistance variation through a Wheatstone bridge, the voltage signal is transmitted to the processor 41 after temperature compensation and differential amplification, and finally the voltage signal representing the resistance variation caused by the deformation of the film of the piezoresistive sensing module 2 under the action of the ampere force is output by the processor 41, so that the pressure self-test of the absolute pressure type MEMS piezoresistive sensor is realized.
Fig. 5 is a flowchart of a self-testing method of an absolute pressure type MEMS piezoresistive sensor according to an embodiment of the present invention, where the method is applied to any of the absolute pressure type MEMS piezoresistive sensors, and specifically includes:
and 11, supplying power to the metal lead module by at least two groups of set voltages so that the metal lead module generates at least two groups of ampere forces towards the piezoresistive sensing module.
And 12, acquiring at least two groups of pressure sensing signals output by the piezoresistive sensing module under the at least two groups of ampere forces.
The pressure sensing signal is a voltage value representing the resistance variation of the piezoresistive sensing module.
Because the electrified metal wire module can generate an ampere force towards the piezoresistive sensing module in a static magnetic field, the thin film layer in the piezoresistive sensing module can deform under the action of the ampere force, so that the resistance value of the piezoresistive strip is changed, and the variation of the resistance value is directly related to the deformation of the thin film layer.
Specifically, at least two sets of set voltages are not simultaneously applied to the metal wire module, but a set of set voltages are applied to control the metal wire module to generate a set of ampere force and obtain a pressure sensing signal output by the piezoresistive sensing module, then a set of set voltages are applied to control the metal wire module to generate a set of ampere force and obtain a pressure sensing signal output by the piezoresistive sensing module again, and the steps are repeated.
And step 13, calculating the sensitivity and the linearity of the piezoresistive sensing module according to the at least two groups of pressure sensing signals.
In order to realize built-in self-test of the absolute pressure type MEMS piezoresistive sensor, the embodiment uses a test voltage excitation signal on the chip as an input, so that the sensitive film of the piezoresistive sensing module can also deform under the condition of not receiving an externally applied force. The controllable switch is used for controlling the working mode of the absolute pressure type MEMS piezoresistive sensor and accessing a power supply voltage signal required by the absolute pressure type MEMS piezoresistive sensor during self-testing. In the self-test mode, a control signal of the controllable switch is generated by the processor, a power supply voltage is provided for self-test through the I/O interface and the digital-to-analog converter, the power supply voltage is connected into the metal lead module, and the energized metal lead module can generate downward ampere force in a magnetic field. And then, corresponding temperature compensation is carried out on the output voltage of the piezoresistive sensing module by combining a temperature compensation circuit, when the magnetic field intensity provided by a magnetic field generating device below the piezoresistive sensing module is unchanged and different test voltages are applied to the metal wire module, the deformation of the sensitive film caused by different ampere force generated in the metal wire module is different. The output signal of the piezoresistive sensor is used for testing the static characteristics of the sensor, such as sensitivity, linearity and the like, according to different testing voltages.
The embodiment adopts the electric signal to provide test excitation for the device, so that the test standardization degree can be improved, the dependence on a complex test instrument is reduced, and the test and product cost is effectively reduced. Meanwhile, after the sensor is put into use for a period of time, various performance indexes of the sensor can still be tested, so that the accuracy of data output by the sensor is ensured, and the normal operation of production and life is ensured.
The technical scheme provided by the embodiment of the invention at least has the following technical effects or advantages:
in the embodiment of the invention, the metal lead module is arranged on one side of the piezoresistive sensing module, and the first magnetic field generating device and the second magnetic field generating device which are arranged near the piezoresistive sensing module form a static magnetic field near the piezoresistive sensing module, so that after the metal lead module is conducted, ampere force towards the piezoresistive sensing module is generated in the static magnetic field, the absolute pressure type MEMS piezoresistive sensor can carry out pressure self-test according to the ampere force, the processes of building off-chip test equipment and repeatedly disassembling the test are omitted, the detection efficiency of the absolute pressure type MEMS piezoresistive sensor is improved, the sensor can realize functional self-test while not depending on the traditional test equipment, and meanwhile, after the sensor is put into use for a period of time, the performance of the sensor can still be tested on the basis of not disassembling the sensor.
While preferred embodiments of the present invention have been described, additional variations and modifications in those embodiments may occur to those skilled in the art once they learn of the basic inventive concepts. Therefore, it is intended that the appended claims be interpreted as including the preferred embodiment and all changes and modifications that fall within the scope of the invention.
It will be apparent to those skilled in the art that various changes and modifications may be made in the present invention without departing from the spirit and scope of the invention. Thus, if such modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include such modifications and variations.
Claims (10)
1. An absolute pressure MEMS piezoresistive sensor, comprising: the piezoresistive sensing module comprises a metal lead module, a piezoresistive sensing module, a first magnetic field generating device, a second magnetic field generating device and a signal processing circuit;
the piezoresistive sensing module comprises: the protective layer, the thin film layer, the silicon substrate layer and the glass layer are stacked; a cavity structure is arranged in the silicon substrate layer; one side of the thin film layer, which is close to the protective layer, is provided with a piezoresistive strip; a metal electrode is arranged on one side of the protective layer, which is far away from the thin film layer; the metal electrode is electrically connected with the piezoresistive strip;
the metal lead module is arranged on one side of the protective layer, which is far away from the thin film layer;
the first magnetic field generating device and the second magnetic field generating device are arranged around the piezoresistive sensing module to jointly provide a static magnetic field for the piezoresistive sensing module;
the signal input end of the signal processing circuit is connected with the signal output end of the piezoresistive sensing module; and the signal processing circuit is respectively connected with the metal wire module and the piezoresistive sensing module in a power supply manner.
2. The absolute pressure MEMS piezoresistive sensor according to claim 1, wherein the metal wire module comprises: the device comprises a first strip-shaped metal electrode, a second strip-shaped metal electrode and at least two metal wires;
the at least two metal wires are connected in parallel between the first strip-shaped metal electrode and the second strip-shaped metal electrode;
the signal processing circuit is electrically connected with the first strip-shaped metal electrode; the second strip-shaped metal electrode is grounded.
3. The absolute pressure MEMS piezoresistive sensor according to claim 2, wherein each of the at least two metal wires is arranged parallel to the protection layer.
4. The absolute pressure MEMS piezoresistive sensor according to claim 3, wherein the cross-sectional shape of the metal wire is rectangular.
5. The absolute pressure MEMS piezoresistive sensor according to any of the claims 2 to 4, wherein the ratio of the length to the cross-sectional area of the metal wire is larger than a set value.
6. The absolute pressure MEMS piezoresistive sensor according to claim 1, wherein the first magnetic field generating device is a first solenoid and the second magnetic field generating device is a second solenoid;
the first magnetic field generating device and the second magnetic field generating device are both arranged on one side, far away from the silicon substrate layer, of the glass layer; wherein the polarities of the magnetic poles of the first magnetic field generating device and the second magnetic field generating device on the side close to the glass layer are opposite;
the signal processing circuit is respectively connected with the first solenoid and the second solenoid in an electric supply way.
7. The absolute pressure MEMS piezoresistive sensor according to claim 1, wherein the first magnetic field generating device is a first monolithic magnet and the second magnetic field generating device is a second monolithic magnet.
8. The absolute pressure MEMS piezoresistive sensor according to claim 1, wherein the first magnetic field generating device is a first pole of a U-shaped magnet and the second magnetic field generating device is a second pole of the U-shaped magnet.
9. The absolute pressure MEMS piezoresistive sensor according to claim 6, wherein the signal processing circuitry comprises a processor, a controllable switch, a digital-to-analog converter, an analog-to-digital converter, a temperature compensation circuit, and a differential amplifier;
the power supply output end of the processor is connected with the first switch input end of the controllable switch through the digital-to-analog converter; the control end of the processor is connected with the switch control end of the controllable switch;
the first switch output end of the controllable switch is grounded through the metal lead module;
a second switch output of the controllable switch is grounded through the first solenoid; a third switch output of the controllable switch is connected to ground through the second solenoid;
the fourth switch output end of the controllable switch is connected with the first bridge input end of the Wheatstone bridge; a second bridge input terminal of the Wheatstone bridge is grounded; a first bridge output end of the Wheatstone bridge is connected with a first input end of the differential amplifier through the temperature compensation circuit; a second bridge output end of the Wheatstone bridge is connected with a second input end of the differential amplifier; the output end of the differential amplifier is connected with the signal input end of the processor through the analog-to-digital converter; wherein the Wheatstone bridge is formed by connecting the piezoresistive strips.
10. A method of self-testing an absolute MEMS piezoresistive sensor according to any of claims 1 to 9, said method comprising:
supplying power to the metal lead module by at least two groups of set voltages so as to enable the metal lead module to generate at least two groups of ampere forces towards the piezoresistive sensing module;
acquiring at least two groups of pressure sensing signals output by the piezoresistive sensing module under the at least two groups of ampere forces; the pressure sensing signal is a voltage value representing the resistance variation of the piezoresistive sensing module;
and calculating the sensitivity and the linearity of the piezoresistive sensing module according to the at least two groups of pressure sensing signals.
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