CN114689225B - Absolute pressure MEMS piezoresistive sensor and self-testing method thereof - Google Patents
Absolute pressure MEMS piezoresistive sensor and self-testing method thereof Download PDFInfo
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
- 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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- B—PERFORMING OPERATIONS; TRANSPORTING
- B81—MICROSTRUCTURAL TECHNOLOGY
- B81B—MICROSTRUCTURAL DEVICES OR SYSTEMS, e.g. MICROMECHANICAL DEVICES
- B81B7/00—Microstructural systems; Auxiliary parts of microstructural devices or systems
- B81B7/02—Microstructural systems; Auxiliary parts of microstructural devices or systems containing distinct electrical or optical devices of particular relevance for their function, e.g. microelectro-mechanical systems [MEMS]
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
- G01L25/00—Testing or calibrating of apparatus for measuring force, torque, work, mechanical power, or mechanical efficiency
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
- G01L27/00—Testing or calibrating of apparatus for measuring fluid pressure
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- G—PHYSICS
- G01—MEASURING; TESTING
- 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 a absolute pressure type MEMS piezoresistive sensor and a self-testing method thereof. In the sensor, a metal wire module is arranged at one side of a protective layer far away from a 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 in power supply connection with the metal wire module and the piezoresistive sensing module. The invention provides a pressure self-testing function of the absolute MEMS piezoresistive sensor, omits the processes of building off-chip testing equipment and repeatedly disassembling and testing, and improves the detection efficiency of the absolute MEMS piezoresistive sensor.
Description
Technical Field
The invention relates to the technical field of piezoresistive sensors, in particular to a absolute pressure type MEMS piezoresistive sensor and a self-testing method thereof.
Background
MEMS (Micro Electro MECHANICAL SYSTEM ) technology is gradually developed by absorbing and integrating other processing technologies based on a microelectronic manufacturing process, and currently, the MEMS technology is frequently applied to the high-tech field requiring small size, high precision, high reliability and low power consumption.
The absolute pressure MEMS piezoresistive sensor belongs to a piezoresistive sensor, can utilize the piezoresistive effect of semiconductor materials to realize the measurement of external pressure, strain and the like, converts external pressure values into electric signals for output, and is widely applied to control systems in the fields of water conservancy and hydropower, railway transportation, aerospace, petrochemical industry, electric power, ship industry and the like.
The absolute pressure type MEMS piezoresistive sensor needs to be detected at fixed time after being put into use, and the absolute pressure type MEMS piezoresistive sensor is subjected to complex physical excitation by adopting high-precision off-chip testing equipment in the prior art, but the existing off-chip testing equipment is usually large-scale and expensive testing equipment, so that the whole testing process is high in cost, time and labor are wasted, and the efficiency is low.
Therefore, how to improve the detection efficiency of the absolute MEMS piezoresistive sensor is a technical problem that needs to be solved at present.
Disclosure of Invention
The invention aims to provide a absolute MEMS piezoresistive sensor and a self-testing method thereof, so as to improve the detection efficiency of the absolute MEMS piezoresistive sensor.
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 MEMS piezoresistive sensor, comprising: the piezoresistance sensing device comprises a metal wire module, a piezoresistance 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; a piezoresistive strip is arranged on one side of the film layer, which is close to the protective layer; a metal electrode is arranged on one side of the protective layer away from the film layer; the metal electrode is electrically connected with the piezoresistive strip;
the metal wire module is arranged on one side of the protective layer away from the 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; the signal processing circuit is respectively in power supply connection with the metal wire module and the piezoresistive sensing module.
In one possible embodiment, the metal wire module includes: 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 in power supply connection 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 cross-sectional shape of the metal wire is rectangular.
In one possible embodiment, the ratio of the length to the cross-sectional area of the metal wire is greater than a set value.
In one 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 arranged on one side of the glass layer, which is far away from the silicon substrate layer; wherein the polarities of the magnetic poles of the first magnetic field generating device and the second magnetic field generating device at the side close to the glass layer are opposite;
the signal processing circuit is respectively in power supply connection with the first solenoid and the second solenoid.
In one 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 pole of a U-shaped magnet, and the second magnetic field generating device is a second 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 wire die;
the second switch output end of the controllable switch is grounded through the first solenoid; the third switch output end of the controllable switch is grounded 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; the second bridge input end of the Wheatstone bridge is grounded; the first bridge output end of the Wheatstone bridge is connected with the first input end of the differential amplifier through the temperature compensation circuit; the second bridge output end of the Wheatstone bridge is connected with the 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 based on the absolute MEMS piezoresistive sensor according to any one of the first aspect, where the method includes:
Supplying power to the metal wire module with at least two sets of set voltages so that the metal wire module generates at least two sets 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 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 wire module is arranged on one side of the piezoresistive sensing module, 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, and after the metal wire module conducts electricity, an ampere force facing the piezoresistive sensing module can be generated in the static magnetic field, so that the absolute MEMS piezoresistive sensor can perform 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 MEMS piezoresistive sensor is improved, the sensor can realize functional self-test while not depending on the traditional test equipment, and meanwhile, the sensor performance can still be tested on the basis of not disassembling the sensor after the sensor is put into use for a period of time.
Drawings
In order to more clearly illustrate the embodiments of the present description or the technical solutions in the prior art, the drawings that are required for the embodiments will be briefly described below, and it is apparent that the drawings in the following description are only some embodiments of the present description, and other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a schematic diagram of a pressure-proof MEMS piezoresistive sensor according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of an arcuate 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 connection diagram of a signal processing circuit according to an embodiment of the present invention;
FIG. 5 is a flow chart of a self-test method of an absolute MEMS piezoresistive sensor according to an embodiment of the present invention.
Reference numerals illustrate: 1 is a metal wire module, 2 is a piezoresistance sensing module, 21 is a protective layer, 22 is a film layer, 221 is a piezoresistance strip, 222 is a metal electrode, 23 is a silicon substrate layer, 231 is a cavity structure, 24 is a glass layer, 31 is a first magnetic field generating device, 32 is a second magnetic field generating device, 4 is a signal processing circuit, 41 is a processor, 42 is a controllable switch, 43 is a digital-analog converter, 44 is an analog-digital converter, 45 is a temperature compensation circuit, and 46 is a differential amplifier.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is apparent that the described embodiments are only some embodiments of the present invention, but not all embodiments, and all other embodiments obtained by those skilled in the art based on the embodiments of the present invention are within the scope of protection 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 piezoresistive sensor comprises a metal wire module 1, a piezoresistive sensor module 2, a first magnetic field generating device 31, a second magnetic field generating device 32 and a signal processing circuit 4.
The piezoresistive sensor module 2 comprises: the protective layer 21, the film layer 22, the silicon substrate layer 23 and the glass layer 24 are stacked, a cavity structure 231 is arranged in the silicon substrate layer 23, a piezoresistive strip 221 is arranged on one side, close to the protective layer 21, of the film layer 22, a metal electrode 222 is arranged on one side, far away from the film layer 22, of the protective layer 21, and the metal electrode 222 is electrically connected with the piezoresistive strip 221.
Specifically, the protective layer 21 may be made of a silicon nitride material, the thin film layer 22 and the silicon substrate layer 23 may be made of silicon wafers of the same material, or a deep silicon etching process may be used 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 may be connected by a bonding process.
In the absolute pressure type MEMS piezoresistive sensor, a movable film layer 22 is arranged on a cavity structure 231, a piezoresistive strip 221 is formed on the surface of the film layer 22 through an ion implantation technology, then the bottom of a silicon substrate layer 23 is bonded with glass to form a vacuum closed cavity, when the top end of the film is subjected to external pressure, the piezoresistive effect of the piezoresistive strip 221 on the surface of the film layer 22 is amplified due to ion implantation, the resistivity of the piezoresistive strip 221 is changed, four piezoresistive strips 221 communicated with the surface of the film form a Wheatstone bridge, and the pressure value born by the surface of the film can be calculated by measuring the output voltage value of the bridge, so that the aim of measuring absolute pressure is fulfilled.
The process of calculating the pressure sensing signal of the absolute MEMS piezoresistive sensor in this embodiment will be briefly described. The piezoresistive sensor module 2 in this embodiment performs pressure detection mainly based on the piezoresistive effect of the material. Piezoresistance is a physical effect that when a metal or semiconductor material is subjected to pressure or tension along a certain crystal plane, the volume of the semiconductor changes, the interior of the crystal lattice of the semiconductor is distorted, so that energy bands change, the mobility and concentration of majority carriers in a conduction band change, and the resistivity changes remarkably.
The amount of change in resistivity (Δρ/ρ) can be expressed as the product of the piezoresistive coefficient and the stress applied, as follows:
Where pi l is the longitudinal piezoresistive coefficient, pi t is the transverse piezoresistive coefficient, σ l is the longitudinal stress, and σ t is the transverse stress.
The piezoresistive material (i.e., piezoresistive strip 221) disposed along axis <100>, which has a specific piezoresistive coefficient of:
πl,＜100>＝π11,πt,＜100>＝π12。
the piezoresistive material (i.e., piezoresistive strip 221) is placed along the axis <110> direction with a specific piezoresistive coefficient of:
the formula of the variation (dR/R) of the resistance value of the material is as follows:
wherein, Is the resistance change of the piezoresistive material caused by the size change factor,/>Is the resistance change of the piezoresistive material caused by the piezoresistive effect.
Since the temperature change is not large in the process of the resistance change of the piezoresistive material caused by the piezoresistive effect, the size change of the piezoresistive material is very weak, and thus the resistance change of the material caused by the piezoresistive effect is much larger than the resistance change caused by the geometric size change, if the size change factor of the material is not considered, the change amount of the resistance can be expressed by the following formula:
after the variation of the resistance is obtained, the pressure of the outside can be represented, so that absolute pressure detection is realized.
The first magnetic field generating device 31 and the second magnetic field generating device 32 are both arranged around the piezoresistive sensor module 2 to jointly provide a static magnetic field for the piezoresistive sensor module 2.
Specifically, the first magnetic field generating device 31 and the second magnetic field generating device 32 are both disposed on the side of the glass layer 24 away from the silicon substrate layer 23; wherein the polarities of the magnetic poles of the first magnetic field generating device 31 and the second magnetic field generating device 32 at the side close to the glass layer 24 are opposite to form an arc-shaped static magnetic field around the piezoresistive sensor module 2.
Specifically, the magnetic induction lines of the first magnetic field generating device 31 and the second magnetic field generating device 32 at the magnetic pole position near the glass layer 24 are perpendicular to the glass layer 24, and the polarities of the two magnetic poles are opposite, so that 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 sensor module 2, as shown in fig. 2, which is a schematic diagram of the arc-shaped static magnetic field distribution provided in the embodiment.
Specifically, the first magnetic field generating device 31 is a first single magnet, the second magnetic field generating device 32 is a second single magnet, and the single magnet may be a cylindrical button magnet or a bar magnet; the first magnetic field generating device 31 may be a first magnetic pole of a U-shaped magnet, and the second magnetic field generating device 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 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 wire module 1 is disposed on one side of the protective layer 21 far away from the thin film layer 22, the signal processing circuit 4 is electrically connected with the metal wire module 1, and due to the existence of a magnetic field near the piezoresistive sensor module 2, after the metal wire module 1 is electrified, the metal wire will generate an ampere force towards the piezoresistive sensor module 2, and due to the fact that the ampere force is related to the electrified current in the metal wire, the embodiment can apply controllable pressure to the piezoresistive sensor module 2 through the metal wire module 1 so as to perform pressure self-test of the absolute pressure type MEMS piezoresistive sensor.
In order to enable the ampere force generated by the metal wire module 1 to uniformly act on the piezoresistive sensor module 2, the present 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, wherein the metal wire module 1 is disposed in the middle of a wheatstone bridge composed of 4 piezoresistive bars 221, and specifically includes: the first strip-shaped metal electrode 222, the second strip-shaped metal electrode 222 and a plurality of (at least two) metal wires which 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 in power supply connection 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, as the intervals of the metal wires are the same and 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 testing is ensured, and the precision of testing is improved.
Specifically, the metal wire can be selected from gold wire, silver wire or aluminum wire, which can generate ampere force in a magnetic field, and can be added above the protective layer through a photoetching process.
Of course, in order to further enable the ampere force generated by the metal wire module 1 to act on the piezoresistive sensor module 2 more uniformly, the cross-sectional shape of each metal wire is rectangular with the same size, and the rectangular wire can act on the piezoresistive sensor module 2 more stably than the circular wire.
Since the metal wire module 1 generates heat at the same time when an ampere force is generated, the heat can affect the size of the piezoresistive strip 221, thereby affecting the accuracy of the absolute MEMS piezoresistive sensor.
In this embodiment, the ratio of the length to the cross-sectional area of each metal wire is greater than a predetermined value, i.e. wires with the length as long as possible and the cross-sectional area as small as possible are selected to form the metal wire module 1, 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 on a single metal wire due to energization is calculated as follows:
Wherein R represents the resistance of a single metal wire, and the unit is 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 units of ohm-meters (Ω -m); p represents the power generated by electrifying on a single metal wire, and the unit is W; v represents the self-test voltage in V, which the CPU inputs into the metal wire module 1.
It can be seen that the length of the single metal wire is as large as possible, the cross-sectional area of the metal wire is as small as possible, the self-test voltage is as small as possible, and the external magnetic field is as large as possible, so that the heat generated by the whole metal wire module 1 structure is as small as possible while the generated ampere force is as large 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, a schematic connection diagram of the signal processing circuit 4 provided in this embodiment is shown, 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 wire module 1; the second switch output of the controllable switch 42 is grounded via the first solenoid; the third switch output of the controllable switch 42 is grounded via a 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; the first bridge output of the wheatstone bridge is connected to the first input of the differential amplifier 46 through the temperature compensation circuit 45; the 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 the connection of piezoresistive strips 221.
Specifically, the processor 41 may be a single chip microcomputer, 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 adopts the controllable switch 42 with one input and one output to reduce the number of switches, the signal processing circuit 4 can be manufactured into a small-sized PCB, so that the metal wire module 1, the piezoresistance sensing module 2, the first magnetic field generating device 31, the second magnetic field generating device 32 and the signal processing circuit 4 can realize tight packaging, and a pressure-proof MEMS piezoresistance sensor with a pressure self-test function is formed.
The working principle of the embodiment is as follows:
In this embodiment, a metal wire module 1 is added on the sensitive film of the piezoresistive sensor module 2 through the MEMS processing technology. When the whole piezoresistance sensing module 2 is in a magnetic field and the metal wire module 1 is electrified, downward ampere force is generated on the metal wire module 1 due to the action of the magnetic field, a sensitive film of the piezoresistance sensing module 2 deforms due to the ampere force, so that the resistance value of a piezoresistor is changed, the piezoresistance sensing module 2 outputs a voltage signal representing the resistance change through a Wheatstone bridge, the voltage signal is transmitted to the processor 41 after temperature compensation and differential amplification, and finally the resistance change, which is output by the processor 41 and is caused by the deformation of the film due to the ampere force, of the piezoresistance sensing module 2 is realized, so that the pressure self-test of the absolute MEMS piezoresistance 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 wire module with at least two groups of set voltages so that the metal wire module generates at least two groups of ampere forces towards the piezoresistive sensing module.
Step 12, obtaining 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 energized metal wire module can generate ampere force towards the piezoresistive sensing module in the 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 change 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 applied to the metal wire module at the same time, but a set of set voltages are applied first 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 again, and the pressure sensing signal output by the piezoresistive sensing module is obtained again, so that the process is repeated.
And step 13, calculating the sensitivity and linearity of the piezoresistive sensing module according to the at least two groups of pressure sensing signals.
In order to realize the built-in self test of the absolute pressure type MEMS piezoresistive sensor, the embodiment uses the test voltage excitation signal on the chip as input, so that the sensitive film of the piezoresistive sensing module can be deformed under the condition of not receiving the externally applied force. The controllable switch is used for controlling the working mode of the absolute MEMS piezoresistive sensor and is connected with a power supply voltage signal required by the absolute MEMS piezoresistive sensor during self-test. In the self-test mode, a control signal of the controllable switch is generated by the processor, and through the I/O interface and the digital-to-analog converter, a power supply voltage is provided for self-test, and the power supply voltage is connected to the metal wire module, so that the electrified metal wire module can generate downward ampere force in a magnetic field. And then, carrying out corresponding temperature compensation on the output voltage of the piezoresistive sensing module by combining a temperature compensation circuit, and when the magnetic field intensity provided by the magnetic field generating device below the piezoresistive sensing module is unchanged and different test voltages are passed to the metal wire module, the deformation of the sensitive film caused by different ampere forces generated in the metal wire module is different. And according to the output signals of the piezoresistive sensor under different test voltages, testing the static characteristics such as sensitivity, linearity and the like of the sensor.
The embodiment adopts the electric signal to provide test excitation for the device, so that the standardization degree of the test can be improved, and the dependence on a complex test instrument can be reduced, thereby effectively reducing the test and product cost. Meanwhile, after the sensor is put into use for a period of time, various performance indexes of the sensor can be tested, so that the accuracy of output data of the sensor is ensured, and normal production and life are ensured.
The technical scheme provided by the embodiment of the invention has at least the following technical effects or advantages:
According to the embodiment of the invention, the metal wire module is arranged on one side of the piezoresistive sensing module, 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, and after the metal wire module is conductive, an ampere force facing the piezoresistive sensing module can be generated in the static magnetic field, so that the absolute MEMS piezoresistive sensor can perform pressure self-test according to the ampere force, the processes of building off-chip test equipment and repeatedly disassembling and testing are omitted, the detection efficiency of the absolute MEMS piezoresistive sensor is improved, the sensor can realize functional self-test while not depending on traditional test equipment, and meanwhile, the sensor performance can still be tested on the basis of not disassembling the sensor after the sensor is put into use for a period of time.
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. It is therefore intended that the following claims be interpreted as including the preferred embodiments and all such alterations and modifications as fall within the scope of the invention.
It will be apparent to those skilled in the art that various modifications and variations can be made to the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention also include such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof.
Claims (9)
1. A pressure-proof MEMS piezoresistive sensor, comprising: the piezoresistance sensing device comprises a metal wire module, a piezoresistance 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; a piezoresistive strip is arranged on one side of the film layer, which is close to the protective layer; a metal electrode is arranged on one side of the protective layer away from the film layer; the metal electrode is electrically connected with the piezoresistive strip;
The metal wire module is arranged on one side of the protective layer away from the film layer; the metal wire module includes: 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 uniformly connected in parallel between the first strip-shaped metal electrode and the second strip-shaped metal electrode;
The signal processing circuit is in power supply connection with the first strip-shaped metal electrode; the second strip-shaped metal electrode is grounded;
the first magnetic field generating device and the second magnetic field generating device are arranged on one side of the glass layer, which is far away from the silicon substrate layer; the polarities of the magnetic poles of the first magnetic field generating device and the second magnetic field generating device at one side close to the glass layer are opposite, so that an arc-shaped static magnetic field is formed 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 in power supply connection with the metal wire module and the piezoresistive sensing module.
2. The absolute MEMS piezoresistive sensor according to claim 1, wherein said at least two metal wires are each arranged parallel to said protective layer.
3. The absolute MEMS piezoresistive sensor according to claim 2, wherein the cross-sectional shape of the metal conductive line is rectangular.
4. A pressure-isolating MEMS piezoresistive sensor according to any of claims 1-3, wherein the ratio of the length of said metal wire to the cross-sectional area is greater than a set value.
5. The absolute MEMS piezoresistive sensor according to claim 1, wherein said first magnetic field generating device is a first solenoid and said second magnetic field generating device is a second solenoid;
the first magnetic field generating device and the second magnetic field generating device are arranged on one side of the glass layer, which is far away from the silicon substrate layer; wherein the polarities of the magnetic poles of the first magnetic field generating device and the second magnetic field generating device at the side close to the glass layer are opposite;
the signal processing circuit is respectively in power supply connection with the first solenoid and the second solenoid.
6. The absolute MEMS piezoresistive sensor according to claim 1, wherein said first magnetic field generating device is a first monolithic magnet and said second magnetic field generating device is a second monolithic magnet.
7. The absolute MEMS piezoresistive sensor according to claim 1, wherein said first magnetic field generating device is a first pole of a U-shaped magnet and said second magnetic field generating device is a second pole of said U-shaped magnet.
8. The absolute MEMS piezoresistive sensor according to claim 5, wherein said 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 wire die;
the second switch output end of the controllable switch is grounded through the first solenoid; the third switch output end of the controllable switch is grounded 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; the second bridge input end of the Wheatstone bridge is grounded; the first bridge output end of the Wheatstone bridge is connected with the first input end of the differential amplifier through the temperature compensation circuit; the second bridge output end of the Wheatstone bridge is connected with the 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.
9. A self-test method based on the absolute MEMS piezoresistive sensor according to any of the claims 1 to 8, characterized in that said method comprises:
Supplying power to the metal wire module with at least two sets of set voltages so that the metal wire module generates at least two sets 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 linearity of the piezoresistive sensing module according to the at least two groups of pressure sensing signals.
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