Real-time liquid flow rate monitoring sensor and method based on MEMS plane resonance technology

Abstract

The invention belongs to the technical field of MEMS resonance sensors, and particularly relates to a real-time liquid flow rate monitoring sensor and method based on an MEMS plane resonance technology. Wherein the fan-shaped sensing plate is an arc plate, a central supporting beam is arranged at the rear end of the middle part of a small arc-shaped edge of the fan-shaped sensing plate, an electrothermal resonance excitation thin beam and a piezoresistive frequency reading thin beam are arranged on the left side and the right side of the fan-shaped sensing plate, and an electrothermal excitation resistor is embedded in the electrothermal resonance excitation thin beam; a piezoresistor is embedded in the piezoresistive frequency reading thin beam; according to the invention, the MEMS resonance technology is applied to the micro flow channel, and the high-precision measurement of the flow velocity of the fluid is realized through the frequency deviation characteristic of the torsional mode resonance generated by electromagnetic excitation under the action of the fluid.

Description

Technical Field

[0001] The present invention belongs to the technical field of MEMS resonant sensors, and particularly relates to a real-time liquid flow rate monitoring sensor and method based on MEMS planar resonance technology. Background Art

[0002] MEMS resonant sensor technology is a sensing method based on microelectromechanical systems, which uses the change of the resonant frequency of a micro-mechanical structure to detect external physical or chemical quantities. Its core principle is to excite resonators at the micron or nanometer scale (such as cantilever beams, thin films or disk structures) to vibrate. When external environmental parameters (such as mass, pressure, temperature or biomolecule adsorption) change, the natural frequency, amplitude or phase of the resonator will change accordingly. High-precision sensing can be achieved by detecting these changes in mechanical vibration characteristics.

[0003] In recent years, the research and application of MEMS resonant sensor technology have shown explosive growth. With its advantages of high sensitivity, miniaturization and integration, it has quickly become one of the focuses in the sensing field. Researchers have successfully developed pressure sensors, accelerometers, mass detectors, gas sensors and biomolecule recognition devices based on the MEMS resonance principle. These devices show broad application prospects in the fields of industrial automation, environmental monitoring, medical diagnosis and consumer electronics.

[0004] Among them, the micro-cantilever beam pressure sensing technology can achieve ultra-sensitive pressure detection at the millimeter or even micron scale. Through a specially designed micro-cantilever beam structure, this technology converts external pressure changes into measurable mechanical deformation or resonant frequency shift, with advantages such as low detection limit, fast response speed and high spatial resolution, promoting the performance improvement and miniaturization integration of pressure sensing devices.

[0005] As a highly promising high-precision sensing solution, the planar resonance sensing technology for large-damping liquid environments can achieve ultra-sensitive detection of physical and chemical parameters in liquid environments at the micron scale. This innovative technology provides a new research means for trace substance analysis in complex liquid systems, research on biomolecule interactions and real-time environmental monitoring. Through a specially designed planar resonance structure, while maintaining a high quality factor (Q value), it effectively overcomes the strong damping effect brought by the liquid environment, significantly improving the sensitivity and reliability of liquid-phase detection, and opening up an important way for the performance improvement and miniaturization integration of biochemical detection devices.

[0006] However, the sensitivity of traditional microcantilever sensing technology is limited by the material stiffness and size, and the signal-to-noise ratio may be insufficient during extremely low-pressure detection. In the liquid phase environment of a microchannel, due to the limitation of sensitivity, the liquid flow rate cannot be accurately measured. Traditional MEMS planar resonance sensing technology is more applied to the measurement of mass, temperature, pressure, molecular adsorption, etc., and its application for liquid flow rate measurement is relatively limited. Summary of the Invention

[0007] To overcome the above problems, the present invention provides a real-time liquid flow rate monitoring sensor and method based on MEMS planar resonance technology. The MEMS resonance technology is applied in a microchannel. Through the frequency shift characteristic of the in-plane torsional pendulum mode resonance generated by electrothermal excitation under the action of the fluid, high-precision measurement of the fluid flow rate is achieved; when the fluid flows through the sensor, the pressure generated by its flow rate causes the microcantilever to deflect controllably. This deflection changes the resonance frequency of the beam, thereby establishing an accurate correspondence relationship of "flow rate - deflection - frequency", and thus being applicable to the measurement of liquid flow rate in a microchannel.

[0008] A real-time liquid flow rate monitoring sensor based on MEMS planar resonance technology includes a central support beam 1, a fan-shaped sensing plate 2, an electrothermal resonance excitation thin beam 3, and a piezoresistive frequency readout thin beam 4; wherein the fan-shaped sensing plate 2 is an arc plate; a central support beam 1 is provided in the middle of the rear end of the fan-shaped sensing plate 2, and an electrothermal resonance excitation thin beam 3 and a piezoresistive frequency readout thin beam 4 are respectively provided at the rear ends of the left and right sides. An electrothermal excitation resistor is buried in the electrothermal resonance excitation thin beam 3 for electrothermal resonance excitation to introduce the fan-shaped sensing plate 2 into in-plane resonance; a piezoresistor is buried in the piezoresistive frequency readout thin beam 4 for piezoresistive frequency readout.

[0009] The front end of the arc plate of the fan-shaped sensing plate 2 is a large arc edge, the rear end is a small arc edge, the left and right sides are respectively straight edges, and the two arc edges are parallel, and the two straight edges are aligned and in a horizontal position. The central support beam 1 is provided at the rear end of the middle of the small arc edge of the fan-shaped sensing plate 2, and the electrothermal resonance excitation thin beam 3 and the piezoresistive frequency readout thin beam 4 are respectively provided at the rear ends of the middle of the straight edges on the left and right sides.

[0010] An electrothermal excitation resistor is implanted in the electrothermal resonance excitation thin beam 3 by ion implantation, and a piezoresistor is implanted in the piezoresistive frequency readout thin beam 4 by ion implantation.

[0011] It further includes leads 5 and electrodes 6. The two ends of the electrothermal resonance excitation thin beam 3 are respectively connected to the corresponding electrodes 6 through the leads 5, and the two ends of the piezoresistive frequency readout thin beam 4 are respectively connected to the corresponding electrodes 6 through the leads 5.

[0012] The width of the central support beam 1 is 16 μm, the thickness is 5 μm, and the length is 45 μm.

[0013] The diameter of the large arc edge at the front end of the sector-shaped sensing plate 2 is 95 μm, the diameter of the small arc edge is 45 μm, the thickness is 5 microns, and the surface area of the sector-shaped sensing plate 2 is 905 μm 2 0.

[0014] The parameters of the electrothermal resonance excitation thin beam 3 and the piezoresistive frequency readout thin beam 4 are both width 2 μm, length 20 μm, and thickness 5 μm.

[0015] A method for measuring the liquid flow rate by changing the resonant frequency of a sensor using liquid pressure. An alternating magnetic field is applied to the electrothermal resonance excitation thin beam 3 to cause the magnetic sensor to generate in-plane torsional pendulum mode resonance. Utilizing the deflection effect of the sensor affected by the flow rate in a fluid environment, when the fluid flows through the sensor, the pressure generated by the flow rate causes the sensor to deflect. During the flow rate measurement, the deflection of the sensor causes a shift in its in-plane torsional pendulum resonant frequency. Through the pre-calibrated flow rate-frequency relationship, the fluid flow rate is deduced inversely from the measured frequency change, realizing high-precision flow rate monitoring.

[0016] A method for measuring the liquid flow rate by changing the resonant frequency of a sensor using liquid pressure, and the specific content is as follows:

[0017] Step 1, connect the electrothermal resonance excitation thin beam 3 to the drive circuit and connect the piezoresistive frequency readout thin beam 4 to the readout circuit. Apply a 2.5V alternating current superimposed with a 2V DC bias voltage to the electrothermal excitation resistor of the electrothermal resonance excitation thin beam 3 through the drive circuit, and obtain the resonance frequency of the sector-shaped sensing plate 2 through the readout circuit connected to the piezoresistive frequency readout thin beam 4;

[0018] Step 2, calibrate the sensitivity of the sensor

[0019] Treat the surface of the entire sensor with PEG-silane at 75°C for 90 minutes, and then rinse the sensor with ethanol and deionized water in sequence to remove surface impurities; immerse the sensor with the surface well-treated in a liquid environment the same as the liquid to be measured. Apply a 2.5V alternating current superimposed with a 2V DC bias voltage to the electrothermal resonance excitation thin beam 3 through the drive circuit to make the sector-shaped sensing plate 2 resonate in the in-plane mode. Then, change the speed of the liquid from 0 to different known flow rates and record the resonance frequency of the sector-shaped sensing plate 2 at different liquid flow rates. Plot a curve with the liquid flow rate as the abscissa and the resonance frequency of the sector-shaped sensing plate 2 as the ordinate to obtain the sensitivity calibration curve as the calibrated flow rate-frequency relationship;

[0020] Step 3, place the calibrated sensor into the liquid with the flow rate to be measured and record its real-time generated resonance frequency;

[0021] Step 4: According to the resonance frequency of the sensor and referring to the calibrated sensitivity curve, obtain the real-time result of the flow rate of the liquid to be measured.

[0022] The present invention provides a preparation method of a real-time liquid flow rate monitoring sensor based on MEMS planar resonance technology, and the specific content is as follows:

[0023] Step 1: Substrate pretreatment

[0024] Cleaning and activation: Take a 5-inch SOI substrate, place it in a mixed solution of acetone and isopropyl alcohol, and ultrasonically clean it for 10 minutes; then perform 5-minute oxygen plasma activation treatment, and finally bake the substrate in a high-temperature furnace at 120°C for 10 minutes to completely remove residual moisture and gas;

[0025] Thermal oxidation to grow an oxide layer: Use a dry-wet process to grow a silicon dioxide layer on the pretreated substrate to obtain a sample; first place the substrate in an environment of 1000°C, perform dry oxygen treatment for 10 minutes to form an initial oxide layer, then perform wet oxygen treatment for 20 minutes to accelerate the oxidation process, so that silicon atoms react fully with oxygen, and finally generate a dense amorphous silicon dioxide layer with a thickness of 200 nm;

[0026] Step 2: Basic structure processing

[0027] Lithography and ion implantation: Adsorb the sample on a spin-coating tray, spin-coat a suitable photoresist to form a uniform photoresist layer, and bake it on a hot plate at 95°C for 90 seconds to cure it; use a lithography machine equipped with a mask template with a specific ion implantation feature pattern for contact exposure, control the ultraviolet light irradiation for 270 milliseconds, and form a latent image of the ion implantation area in the photoresist layer; after exposure, immerse the sample in a 2.38% TMAH developer for 40 seconds to dissolve the unexposed photoresist and achieve pattern transfer; then bake it on a hot plate at 100°C for 2 minutes; use an RIE device, set the etching power to 120 W, the CHF3 gas flow rate to 30 sccm, and the etching time to 5 minutes to etch through the 200-nm silicon dioxide layer to open a channel for ion implantation; then perform boron ion implantation with a dose of 1E15 / cm 3 , an energy of 75 keV, and remove the photoresist after implantation;

[0028] Front-side Structure Etching and Annealing: Spin-coat photoresist on the sample processed as above and cure it. Use the photomask of the front-side structure features of the sensor for photolithography. After contact exposure for 270 milliseconds, develop it. After development, bake it on a hot plate at 100 °C for 2 minutes. Use a deep silicon etching equipment, with a mixed gas of SF6 and C4F8 as the etching gas, SF6 flow rate of 100 - 200 sccm, C4F8 flow rate of 20 - 50 sccm, etching power of 500 - 800 W, etching depth of 5 μm, minimum line width of 4 μm, etch through the 5-μm-thick silicon dioxide layer to form the front-side structure, and remove the photoresist after etching; Finally, place the sample in an environment of dry oxygen and wet oxygen at 1000 °C, and oxidize it for 10 minutes and 20 minutes respectively; Then use RIE equipment to remove the excess silicon dioxide layer;

[0029] Step 3: Fabrication of the Functional Layer

[0030] Electrode Fabrication: Spin-coat photoresist on the substrate and cure it. Use the metal lift-off feature pattern photomask to coat the entire surface with photoresist but do not expose it for now; Through magnetron sputtering technology, deposit a 20-nm-thick Cr and a 300-nm-thick Au on the substrate surface according to the designed area to form the lead 5 and electrode 6 structures; Then perform the metal lift-off operation to remove the excess sputtered material and retain the required electrode 6 pattern; Anneal the sample at 425 °C for 30 minutes;

[0031] Insulating Layer Preparation: Use PECVD equipment to deposit a 500-nm-thick SiO2 insulating layer on the substrate surface to cover the lead 5; After deposition, spin-coat photoresist and cure it. Use the insulating layer feature pattern photomask to coat the entire surface with photoresist, and then use RIE equipment, set the etching power to 180 W, CHF3 gas flow rate to 50 sccm, and etching time to 9 minutes, etch the 500-nm-thick SiO2 insulating layer to form the required insulating layer pattern, and remove the photoresist after etching;

[0032] Step 4: Post-processing of the Device

[0033] Back-side Processing and Structure Release: Spin-coat photoresist on the back side of the substrate and cure it. Use the photomask of the back cavity etching features of the sensor for photolithography, and determine the exposure method and time according to the actual process. After exposure, develop it; After development, bake it on a hot plate at 100 °C for 2 minutes; Use a deep silicon etching equipment to etch the substrate silicon by 400 μm to form the back cavity structure, and remove the photoresist after etching; Place the sample in an HF solution to release the 0.5-μm-thick buried oxide layer;

[0034] Cutting and Shaping: Use a laser stealth cutting equipment to cut the processed substrate according to the predetermined size to complete the fabrication of the sensor.

[0035] Advantages of the Present Invention:

[0036] The present invention innovatively adopts an in-plane in-situ rotational vibration design. By realizing the optimized conversion of vibration modes in a liquid environment, the vibration quality factor of the sensor is significantly improved. This design converts the traditional squeeze-film damping into sliding-film damping, effectively reducing the energy dissipation of the liquid medium on the vibration system. At the same time, the in-situ rotation mechanism further improves the characteristics of the fluid boundary layer, resulting in a further reduction of the sliding-film damping. This dual drag reduction enables the sensor to maintain a very high vibration quality factor in a liquid environment, greatly improving the sensitivity of the sensor.

[0037] The present invention adopts an innovative fan-shaped large-area pressure-sensing structure design. By systematically optimizing the mechanical properties and spatial distribution of the pressure-sensing area, the overall performance of the sensor is improved. This design significantly enhances the pressure response sensitivity by increasing the pressure-sensing area. At the same time, the fan-shaped symmetric layout effectively balances the distribution of fluid impact forces, ensuring the stability of the measurement process. The special geometric configuration design minimizes the influence of flow field disturbances on the measurement results, enabling the sensor to maintain its miniaturization characteristics while achieving a significant improvement in detection performance compared to traditional methods. The overall optimized structure design not only improves the sensitivity of the sensor but also enhances its adaptability in complex flow field environments, providing a reliable technical guarantee for accurate flow velocity measurement.

[0038] In the present invention, by combining the high-quality factor in-plane vibration mode with intelligent signal processing technology, a breakthrough improvement in the flow velocity detection performance in a liquid environment is achieved. Based on the unique shear motion characteristics of the in-plane vibration mode, the sensor has a high quality factor in a liquid environment, which is an order of magnitude higher than that of the traditional out-of-plane vibration mode. Through the optimized electrothermal excitation and piezoresistive detection scheme, the system realizes a complete closed-loop measurement process from signal excitation, resonance detection to flow velocity calculation. The intelligent processing algorithm effectively compensates for the influence of changes in liquid viscosity and temperature by establishing a non-linear mapping relationship between fluid parameters and frequency response, enabling the sensor to maintain excellent stability in complex environments. Brief Description of the Drawings

[0039] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings used in the description of the embodiments of the present invention.

[0040] Figure 1 It is a schematic structural diagram of the sensor of the present invention.

[0041] Figure 2 It is a schematic diagram of the detailed arrangement of the circuit structure of the sensor of the present invention.

[0042] Figure 3 It is a schematic diagram of the overall structure of the circuit arrangement of the sensor of the present invention.

[0043] Figure 4Schematic diagram of the modal simulation analysis results of the sensor of the present invention.

[0044] Figure 5 Schematic diagram of the transient deformation simulation results of the sensor of the present invention under electrothermal excitation.

[0045] Figure 6 Schematic diagram of the steady-state deformation simulation results of the sensor of the present invention under different out-of-plane pressures.

[0046] Figure 7 Schematic diagram of the simulation results of the change in in-plane resonance frequency of the sensor of the present invention under different out-of-plane pressures.

[0047] Figure 8 Process diagram of the flow rate measurement of the sensor of the present invention.

[0048] Figure 9 Flow chart of the preparation of the sensor of the present invention. Detailed implementation manners

[0049] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It can be understood that the specific embodiments described herein are only used to explain the present invention, rather than limiting the present invention.

[0050] Embodiment 1

[0051] A real-time liquid flow rate monitoring sensor based on MEMS planar resonance technology includes a central support beam 1, a sector-shaped sensing plate 2, an electrothermal resonance excitation thin beam 3, and a piezoresistive frequency readout thin beam 4; wherein the sector-shaped sensing plate 2 is an arc plate, the front end of the arc plate is a large arc edge, the rear end is a small arc edge, the left and right sides are straight edges respectively, and the two arc edges are parallel, and the two straight edges are aligned and in a horizontal position; a central support beam 1 is provided at the rear end of the middle of the small arc edge of the sector-shaped sensing plate 2, and an electrothermal resonance excitation thin beam 3 and a piezoresistive frequency readout thin beam 4 are respectively provided at the rear ends of the middle parts of the straight edges on the left and right sides, and an electrothermal excitation resistor is buried in the electrothermal resonance excitation thin beam 3 for electrothermal resonance excitation to introduce the sector-shaped sensing plate 2 into in-plane resonance; a piezoresistive resistor is buried in the piezoresistive frequency readout thin beam 4 for piezoresistive frequency readout.

[0052] The electrothermal excitation resistor is implanted in the electrothermal resonance excitation thin beam 3 by ion implantation, and the piezoresistive resistor is implanted in the piezoresistive frequency readout thin beam 4 by ion implantation.

[0053] It further includes leads 5 and electrodes 6, wherein the two ends of the electrothermal resonance excitation thin beam 3 are respectively connected to the corresponding electrodes 6 through the leads 5, and the two ends of the piezoresistive frequency readout thin beam 4 are respectively connected to the corresponding electrodes 6 through the leads 5.

[0054] The central support beam 1 has a width of 16 μm, a thickness of 5 μm, and a length of 45 μm.

[0055] The diameter of the large arc edge at the front end of the sector-shaped sensing plate 2 is 95 μm, the diameter of the small arc edge is 45 μm, the thickness is 5 μm, and the surface area of the sector-shaped sensing plate 2 is 9050 μm 2 .

[0056] The parameters of the electrothermal resonance excitation thin beam 3 and the piezoresistive frequency readout thin beam 4 are both a width of 2 μm, a length of 20 μm, and a thickness of 5 μm.

[0057] The materials of the central support beam 1, the sector-shaped sensing plate 2, the electrothermal resonance excitation thin beam 3, and the piezoresistive frequency readout thin beam 4 are all silicon.

[0058] The sector-shaped sensing plate 2 is made of silicon (ρ = 2328 kg / m 3 , E = 1.7×10 11 Pa, ν = 0.273).

[0059] A method for measuring the liquid flow rate by changing the resonance frequency of a sensor using liquid pressure. An alternating magnetic field is applied to the electrothermal resonance excitation thin beam 3 to cause the magnetic sensor to generate in-plane torsional pendulum mode resonance. Utilizing the deflection effect of the sensor affected by the flow rate in the fluid environment, when the fluid flows through the sensor, the pressure generated by the flow rate causes the sensor to deflect. During the flow rate measurement, the deflection of the sensor causes a shift in its torsional resonance frequency. Through a pre-calibrated flow rate-frequency relationship, that is, by inversely calculating the flow rate from the measured frequency change, high-precision flow rate monitoring is achieved.

[0060] A method for measuring the liquid flow rate by changing the resonance frequency of a sensor using liquid pressure, the specific content is as follows:

[0061] Step 1, connect the electrothermal resonance excitation thin beam 3 to the drive circuit through the electrode 6 connected to it, and connect the piezoresistive frequency readout thin beam 4 to the readout circuit through the electrode 6 connected to it. For the electrothermal excitation, the drive circuit applies a 2.5 V alternating current superimposed with a 2 V DC bias voltage to the electrothermal excitation resistor of the electrothermal resonance excitation thin beam 3. For the piezoresistive frequency readout, with the help of the readout circuit connected to the piezoresistive frequency readout thin beam 4, the resonance frequency of the sector-shaped sensing plate 2 is obtained (the readout circuit reads the signal of the current changing with time, and then transmits this signal to the network analyzer to obtain the resonance frequency);

[0062] The electrothermal resonance excitation thin beam 3 has a thermal excitation resistor buried in it for electrothermal resonance excitation to introduce the sector-shaped sensing plate 2 into in-plane resonance; the piezoresistive frequency readout thin beam 4 is used for piezoresistive frequency readout. When its piezoresistive resistor is subjected to pulse compression, its frequency signal can be read out. Specifically:

[0063] The excitation resistor and the piezoresistive resistor are respectively embedded in the corresponding thin beams of silicon by boron doping. When a pulsed current is provided through the thermal excitation resistor, the pulsed heating will cause the length of the electrothermal resonance excitation thin beam 3 to expand, thereby introducing the fan-shaped sensing plate 2 into in-plane resonance. On the other hand, the piezoresistive resistor of the piezoresistive frequency readout thin beam 4 is pulsed compressed, and the frequency signal can be read out, so as to measure the change in the resonance frequency of the sensor, and then achieve high-precision measurement of the fluid flow rate.

[0064] Step 2: Calibrate the sensitivity of the sensor with the connected circuit

[0065] Treat the surface of the entire sensor with PEG-silane (PEG-silane: ethanol: deionized water = 1:100:1, volume ratio) at 75°C for 90 minutes, and then rinse the sensor with ethanol and deionized water in turn to remove surface impurities; Immerse the sensor with the surface treated in the same liquid environment as the liquid to be measured. Apply a 2.5V alternating current superimposed with a 2V DC bias voltage to the electrothermal resonance excitation thin beam 3 through the drive circuit to make the fan-shaped sensing plate 2 resonate in the in-plane mode, and then change the speed of the liquid from 0 to different known flow rates. Record the resonance frequency of the fan-shaped sensing plate 2 at different known flow rates of the liquid. Plot a curve with the liquid flow rate as the abscissa and the resonance frequency of the fan-shaped sensing plate 2 as the ordinate to obtain the sensitivity calibration curve as the calibrated flow rate-frequency relationship;

[0066] Step 3: Place the calibrated sensor into the liquid with the flow rate to be measured and record the real-time resonance frequency generated

[0067] Step 4: According to the resonance frequency of the sensor, compare it with the calibrated sensitivity curve to obtain the real-time result of the flow rate of the liquid to be measured and the flow rate change data during the measurement process.

[0068] Embodiment 2

[0069] A method for accurately measuring the liquid flow rate in a microchannel. The present invention applies MEMS resonance technology to the field of liquid measurement. Different from the traditional vertical resonance mode being affected by the damping force in the liquid, the present invention proposes an in-plane resonance mode cantilever beam sensor to overcome the problem of significant damping effect in the liquid medium, so as to achieve real-time liquid flow rate measurement with high quality factor and high sensitivity in the microchannel.

[0070] In this embodiment, on the one hand, a device structure of a real-time liquid flow rate monitoring sensor based on MEMS planar resonance technology is provided.

[0071] Specifically, as Figure 1As shown, the above-mentioned real-time liquid flow velocity monitoring sensor based on MEMS planar resonance technology includes a central support beam 1, a sector-shaped sensing plate 2, an electrothermal resonance excitation thin beam 3, and a piezoresistive frequency readout thin beam 4.

[0072] In this embodiment, the materials of the central support beam 1, the sector-shaped sensing plate 2, the electrothermal resonance excitation thin beam 3, and the piezoresistive frequency readout thin beam 4 are all silicon. The present invention designs a structure composed of the central support beam 1 and the thin beams on both sides, optimizes the distance between the thin beams and the central support beam 1, realizes high resonance frequency and low liquid resistance, and the in-plane resonance signal is detected by the piezoresistive microbeam.

[0073] The central support beam 1 is made of single-crystalline silicon material, and the key parameters are set as the width, thickness, and length of the central support beam 1, so that it can support the deflection and vibration of the sensing plate and meet the specific design requirements for the use purpose.

[0074] Specifically, as Figure 2 shown, the detailed parameters of the sensor are: the width of the central support beam 1 is 16 μm, the thickness is 5 μm; the outer diameter of the sector-shaped sensing plate 2 is 95 μm, the inner diameter is 45 μm, and the thickness is 5 microns. Among them, the area of the sector-shaped sensing plate 2 is 9050 μm 2 ; the parameters of the electrothermal resonance excitation thin beam 3 and the piezoresistive frequency readout thin beam 4 are both width 2 μm, length 20 μm, and thickness 5 μm. Among them, as Figure 2 shown, in the electrothermal resonance excitation thin beam 3, an electrothermal excitation resistor is implanted by ion implantation, and a piezoresistor is implanted in the piezoresistive frequency readout thin beam 4 by ion implantation; after the ion implantation in the electrothermal resonance excitation thin beam 3 and the piezoresistive frequency readout thin beam 4 is completed, the leads 5 of the sensor are arranged around the electrothermal drive and the piezoresistive detection signal transmission, buried in the central support beam 1 and the sector-shaped sensing plate 2, and the material is Au, which is used to connect the electrothermal excitation resistor to transmit the current required for electrothermal drive and connect the piezoresistive sensitive resistor, and lead out the weak electrical signal generated by the piezoresistive change of the piezoresistive frequency readout thin beam 4 during the resonance of the sector-shaped sensing plate 2.

[0075] Specifically, as Figure 3 shown, the overall arrangement of the sensor circuit is that the leads 5 are respectively led out from above the sensing area and finally led to four electrodes 6 with the same size. The size of each electrode 6 is 500 μm × 500 μm, which is used to deliver the drive current to the leads 5 and lead out the readout signal from the leads 5.

[0076] Among them, the two left electrodes 6 are respectively connected to both ends of the electrothermal resonance excitation thin beam 3 through the leads 5, and the two right electrodes 6 are respectively connected to both ends of the piezoresistive frequency readout thin beam 4 through the leads 5.

[0077] In this embodiment, a professional simulation software is used to perform modal simulation on the designed cantilever beam sensor.

[0078] Specifically, as Figure 4 shown, it can be concluded from the simulation analysis results that the designed sensor has an obvious in-plane resonance mode at a characteristic frequency of 6.2418E5, which proves the rationality of the designed sensor size and provides theoretical support for subsequent relevant simulations of the sensor.

[0079] The present invention provides a method for measuring the liquid flow rate by using the bending offset of the sensing plate caused by the liquid pressure to change the resonance frequency:

[0080] The resonance excitation and sensing mechanism of the microcantilever beam and how to measure the flow rate through the frequency shift.

[0081] The electrothermal excitation device applies an alternating magnetic field to the free end of the cantilever beam, that is, the electrothermal resonance excitation thin beam 3, to make the magnetic sensor generate an in-plane torsional pendulum mode resonance. The amplitude I of the excitation current determines the resonance intensity. The length L of the central support beam 1 (the distance from the bottom of the central support beam 1 to the inner circle of the sector-shaped sensing plate 2) affects its natural frequency, and the area S of the sector-shaped sensing plate 2 determines its sensitivity to the fluid pressure.

[0082] Utilizing the deflection effect generated by the sensor affected by the flow rate in the fluid environment, when the fluid flows through the sensor, the pressure F(v) generated by the flow rate v causes the sensor to deflect by δ.

[0083] Utilizing the quantitative relationship between the deflection δ and the resonance frequency to achieve the flow rate measurement; during the flow rate measurement process, the deflection of the sensor causes its torsional resonance frequency f to shift by Δf. Through the pre-calibrated "flow rate - deflection - frequency" relationship model, that is, the fluid flow rate is inversely deduced from the measured frequency change to achieve high-precision flow rate monitoring.

[0084] As Figure 8 shown, it specifically includes the following steps:

[0085] Step S1-1: Prepare the sensor and connect the circuit

[0086] In this embodiment, a cantilever beam sensor with optimized design, good manufacturing, and excellent test performance is selected. Ensure that the sensor frame is coated with insulating silica gel to avoid leakage in conductive liquids. Connect the electrothermal resonance excitation thin beam 3 to the phase-locked loop (PLL) interface circuit. The phase-locked loop (PLL) interface circuit applies a 2.5V alternating current superimposed with a 2V direct current bias voltage to the electrothermal resonance excitation thin beam 3 by connecting to two circuits 6 on the electrothermal resonance excitation thin beam 3. Connect the piezoresistive frequency readout thin beam 4 to the frequency readout circuit to ensure stable circuit connection. Among them, the frequency readout circuit is connected to the circuit 6 connected to the piezoresistive frequency readout thin beam 4 to achieve frequency reading; the electrothermal excitation is achieved by applying a 2.5V alternating current superimposed with a 2V direct current bias voltage on the heating resistor. The piezoresistive frequency readout uses a Wheatstone bridge connected to the piezoresistive frequency readout thin beam 4 and an AD-620 amplifier to input the signal into a network analyzer and read the resonance frequency of the sector-shaped sensing plate 2.

[0087] Step S1-2: Calibrate the sensitivity of the sensor with the connected wires. Treat the entire surface of the sensor with PEG-silane (PEG-silane: ethanol: deionized water = 1:100:1, volume ratio) at 75°C for 90 minutes, and then rinse the sensor with ethanol and deionized water in sequence to remove surface impurities; immerse the sensor with the treated surface in the same liquid environment as the liquid to be measured. Apply a 2.5V alternating current superimposed with a 2V direct current bias voltage to the electrothermal resonance excitation thin beam 3 through the phase-locked loop (PLL) interface circuit to make the sector-shaped sensing plate 2 resonate in the in-plane mode, and make the speed of the liquid change from 0 to different known flow rates for flow. Record the resonance frequency of the sector-shaped sensing plate 2 at different flow rates, plot a curve with the body fluid flow rate as the abscissa and the resonance frequency of the sector-shaped sensing plate 2 as the ordinate to complete the sensitivity calibration;

[0088] Step S1-3: Place the calibrated sensor into the liquid with the flow rate to be measured and record the resonance frequency generated in real time;

[0089] In this embodiment, when the cantilever beam is immersed in the liquid to be measured, different flow rates of the liquid to be measured will apply different pressures on the sector-shaped sensing plate 2, resulting in corresponding deflections of the central cantilever beam 1 and the sector-shaped sensing plate 2. Different deflection degrees will cause the resonance frequency of the sensor device to shift. By recording and analyzing the shift amount of the sensor resonance frequency, the real-time flow rate of the liquid to be measured can be obtained.

[0090] Step S1-4: According to the recorded resonance frequency of the sensor and the calibrated sensitivity, that is, the curve obtained in step S1-2, the real-time result of the flow rate of the liquid to be measured and the flow rate change data during the measurement process can be obtained.

[0091] After adopting the above method of measuring the liquid flow rate by using the liquid pressure to cause the bending and offset of the sector-shaped sensing plate 2 to change the resonance frequency, the following beneficial effects are obtained:

[0092] This embodiment is based on MEMS resonance technology. Through in-plane in-situ rotational vibration design, the vibration mode is optimized, the squeeze film damping is converted into synovial membrane damping, the energy dissipation is reduced, and the vibration quality factor and sensitivity are improved; the innovative sector-shaped large-area pressure-sensing structure design increases the pressure-sensing area, balances the distribution of fluid impact force, reduces the influence of flow field disturbance, and comprehensively improves the sensor performance and adaptability to complex flow fields; in addition, the combination of the high-quality factor in-plane vibration mode and intelligent signal processing technology realizes closed-loop measurement, and the intelligent algorithm compensates for the influence of liquid viscosity and temperature changes, enhancing the stability of the sensor in complex environments, which has great significance in the field of microchannel liquid flow rate measurement.

[0093] In this embodiment, a simulation analysis is carried out on a real-time liquid flow rate monitoring sensor based on MEMS planar resonance technology:

[0094] The simulation analysis part includes the transient deformation simulation analysis of the electrothermal drive of the cantilever beam sensor and the out-of-plane pressure steady-state deformation simulation analysis. Using professional simulation software, the model of the in-plane resonant cantilever beam sensor is pre-drawn. By adding relevant physical fields and setting parameters, the in-plane resonance situation of the cantilever beam and the sensing plate under the thermal excitation generated by the input of the electrical signal and the obvious in-plane resonance mode at a specific characteristic frequency can be finally obtained.

[0095] Specifically, as Figure 5 shown, in the professional simulation software, a model of the central support beam 1, the sector-shaped sensing plate 2, the electrothermal resonance excitation thin beam 3, and the piezoresistive frequency readout thin beam 4 of the sensor is established. Silicon is selected as the material, the electrostatic and solid mechanics physical fields are selected and relevant parameters are set. A transient deformation simulation analysis of the thermoelectric effect is carried out by setting a 2V DC bias voltage and a 2.5V AC voltage with a frequency of 436KHz superimposed electric field at the electrothermal resonance excitation thin beam 3. Finally, the simulation result of the most obvious in-plane resonance of the sensor within a vibration cycle is obtained.

[0096] Specifically, as Figure 6As shown in the figure, a model of the central support beam 1, sector-shaped sensing plate 2, electrothermal resonance excitation thin beam 3, and piezoresistive frequency readout thin beam 4 of the sensor is established in professional simulation software. Silicon is selected as the material, the physical field of solid mechanics is selected, and relevant parameters are set according to the approximate pressure range to be measured. A steady-state deformation simulation analysis of the sensor under a pressure change of 0 - 9000 Pa is carried out. Finally, the simulation results of the overall deflection of the sensor corresponding to 0 Pa, 3000 Pa, 6000 Pa, and 9000 Pa under the condition of a scale factor of 70 are obtained. The results reflect that the designed sensor can produce an obvious deflection phenomenon under the pressure within the required measurement range.

[0097] Specifically, as Figure 7 shown in the figure, data analysis is carried out on the results of the change in the in-plane resonance frequency during the steady-state deformation simulation analysis of the sensor under a pressure change of 0 - 9000 Pa in professional drawing software. It is obtained that the in-plane resonance frequency of the sensor increases as the applied pressure increases, and the sensitivity also increases accordingly. At the same time, the deviation degree of its in-plane resonance frequency is about 1.5%, meeting the measurement standard of MEMS resonant sensors.

[0098] In this embodiment, through multi-faceted simulation of the overall central support beam 1, sector-shaped sensing plate 2, electrothermal resonance excitation thin beam 3, and piezoresistive frequency readout thin beam 4 of the sensor core components, a relatively clear operating condition of the sensor during operation can be obtained, which is helpful for the structural optimization design and related performance testing of the sensor.

[0099] In this embodiment, in the fourth aspect, a preparation method for a real-time liquid flow rate monitoring sensor based on MEMS in-plane resonance technology is provided. As Figure 9 shown in the figure, it includes the following steps:

[0100] Step S2-1: Substrate pretreatment

[0101] Cleaning and activation: Take a 5-inch SOI substrate, put it into a mixed solution of acetone and isopropyl alcohol, and ultrasonically clean it for 10 minutes. With the help of ultrasonic vibration and solution dissolution, remove surface oil stains, organic substances and other impurities; then carry out 5 minutes of oxygen plasma activation treatment. Utilize the high activity of the plasma to further remove stubborn pollutants, and at the same time enhance the surface activity of the substrate and the bonding force of subsequent processes. Finally, place the substrate in a high-temperature furnace at 120 °C and bake it for 10 minutes to completely remove residual moisture and gas, ensuring that the substrate surface is dry and clean, providing a good foundation for subsequent processes;

[0102] Thermal oxidation growth of oxide layer: A silicon dioxide layer is grown on the pretreated substrate by a dry-wet process to obtain a sample; First, the substrate is placed in an environment of 1000 °C, and dry oxygen treatment is carried out for 10 minutes to form an initial oxide layer with a dense structure and few defects. Then, wet oxygen treatment is carried out for 20 minutes to accelerate the oxidation process, enabling silicon atoms to fully react with oxygen, and finally a dense amorphous silicon dioxide layer with a thickness of 200 nm is formed; This oxide layer plays important roles such as insulation and masking in subsequent processes.

[0103] Step S2-2: Fabrication of basic structure

[0104] Lithography and ion implantation: The sample is adsorbed on a spin coater tray, and a suitable photoresist is spin-coated to form a uniform photoresist layer, which is cured on a hot plate at 95 °C for 90 seconds; A mask aligner configured with a specific ion implantation feature pattern mask is used for contact exposure, controlling the ultraviolet light irradiation for 270 milliseconds to form a latent image of the ion implantation area in the photoresist layer; After exposure, the sample is immersed in a 2.38% TMAH developer for 40 seconds to dissolve the unexposed photoresist, realizing pattern transfer; Subsequently, it is baked on a hot plate at 100 °C for 2 minutes to enhance the adhesion and etching resistance of the photoresist. Using an RIE device, the etching power is set to 120 W, the CHF3 gas flow rate is 30 sccm, and the etching time is 5 minutes to etch through the 200 nm silicon dioxide layer to open a channel for ion implantation; Then, boron ions are implanted with a dose of 1E15 / cm 3 , an energy of 75 keV, to change the electrical properties of specific regions of the substrate. After implantation, the photoresist is removed;

[0105] Etching and annealing of the front structure: Photoresist is spin-coated and cured again on the sample after the above treatment. Lithography is carried out using a mask aligner for the front structure feature pattern, developed after contact exposure for 270 milliseconds, and baked on a hot plate at 100 °C for 2 minutes after development to enhance the performance of the photoresist. A deep silicon etching device is used, with a mixed gas of SF6 and C4F8 as the etching gas, an SF6 flow rate of 100 - 200 sccm, a C4F8 flow rate of 20 - 50 sccm, an etching power of 500 - 800 W, an etching depth of 5 um, and a minimum line width of 4 um. The 5 um thick silicon dioxide layer (5 um is removed) is etched through to form the front structure. After etching, the photoresist is removed; Finally, the sample is placed in an environment of dry oxygen and wet oxygen at 1000 °C, oxidized for 10 minutes and 20 minutes respectively, to eliminate the stress generated by etching, repair the crystal structure damage, and improve the material performance; Then, the RIE device is used to remove the excess silicon dioxide layer;

[0106] Step S2-3: Fabrication of functional layer

[0107] Electrode Fabrication: Spin-coat and cure photoresist on the substrate. Use a metal lift-off feature pattern mask to spin-coat the entire surface with photoresist but do not expose it for now. Through magnetron sputtering technology, deposit a 20-nm-thick Cr and a 300-nm-thick Au on the substrate surface according to the designed area to form the gold wire, i.e., the lead 5 and the electrode 6 structure. Then perform the metal lift-off operation to remove the excess sputtered material and retain the desired electrode 6 pattern. Anneal the sample at 425 °C for 30 minutes to improve the adhesion between the metal and the substrate and enhance the electrical properties of the metal electrode.

[0108] Insulating Layer Preparation: Use PECVD equipment to deposit a 500-nm-thick SiO2 insulating layer on the substrate surface to cover the lead 5 and prevent electrical short circuits. After deposition, spin-coat and cure photoresist, use an insulating layer feature pattern mask to spin-coat the entire surface with photoresist, and then use RIE equipment. Set the etching power to 180 W, the CHF3 gas flow rate to 50 sccm, and the etching time to 9 minutes to etch the 500-nm-thick SiO2 insulating layer to form the desired insulating layer pattern. Remove the photoresist after etching.

[0109] Step S2-4: Device Post-processing

[0110] Backside Processing and Structure Release: Spin-coat and cure photoresist on the backside of the substrate. Use a sensor back cavity etching feature pattern mask for lithography, and determine the exposure method and time according to the actual process. Develop after exposure. Bake on a hot plate at 100 °C for 2 minutes after development to enhance the adhesion and etching resistance of the photoresist. Use deep silicon etching equipment to etch the substrate silicon by 400 μm to form the back cavity structure. Remove the photoresist after etching. Place the sample in an HF solution to release the 0.5-μm-thick buried oxide layer. Achieve device structure release to enable the device to have the expected mechanical and electrical functions.

[0111] Cutting and Shaping: Use a laser stealth cutting device to cut the processed substrate according to the predetermined size. Determine the cutting speed and other parameters according to the actual process. Through cutting, separate the substrate into individual devices to complete the sensor fabrication, facilitating subsequent packaging and application.

[0112] The preferred embodiments of the present invention have been described in detail above in conjunction with the accompanying drawings. However, the protection scope of the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, any person skilled in the art within the technical scope disclosed by the present invention can make equivalent substitutions or changes according to the technical solution and inventive concept of the present invention. These simple variations all fall within the protection scope of the present invention.

Claims

1. A real-time liquid flow rate monitoring sensor based on MEMS planar resonance technology, characterized in that It includes a central support beam (1), a sector-shaped sensing plate (2), an electrothermal resonance excitation thin beam (3) and a piezoresistive frequency readout thin beam (4); wherein the sector-shaped sensing plate (2) is an arc plate; in the middle of the rear end of the sector-shaped sensing plate (2), there is a central support beam (1), and at the rear ends of the left and right sides respectively, there are an electrothermal resonance excitation thin beam (3) and a piezoresistive frequency readout thin beam (4). And an electrothermal excitation resistor is buried in the electrothermal resonance excitation thin beam (3) for electrothermal resonance excitation to introduce the sector-shaped sensing plate (2) into in-plane resonance; a piezoresistor is buried in the piezoresistive frequency readout thin beam (4) for piezoresistive frequency readout.

2. The real-time liquid flow rate monitoring sensor based on MEMS planar resonance technology according to claim 1, characterized in that, The front end of the arc plate of the sector-shaped sensing plate (2) is a large arc edge, the rear end is a small arc edge, the left and right sides are respectively straight edges, and the two arc edges are parallel, and the two straight edges are aligned and in a horizontal position. In the middle of the rear end of the small arc edge of the sector-shaped sensing plate (2), there is a central support beam (1), and at the middle of the rear ends of the straight edges on the left and right sides respectively, there are an electrothermal resonance excitation thin beam (3) and a piezoresistive frequency readout thin beam (4).

3. A real-time liquid flow rate monitoring sensor based on MEMS planar resonance technology according to claim 1, characterized in that, In the electrothermal resonance excitation thin beam (3), an electrothermal excitation resistor is implanted by means of ion implantation, and in the piezoresistive frequency readout thin beam (4), a piezoresistor is implanted by means of ion implantation.

4. A real-time liquid flow rate monitoring sensor based on MEMS planar resonance technology according to claim 1, characterized in that, It also includes leads (5) and electrodes (6), wherein the two ends of the electrothermal resonance excitation thin beam (3) are respectively connected to the corresponding electrodes (6) through leads (5), and the two ends of the piezoresistive frequency readout thin beam (4) are respectively connected to the corresponding electrodes (6) through leads (5).

5. The real-time liquid flow rate monitoring sensor based on MEMS planar resonance technology according to claim 1, wherein The width of the central support beam (1) is 16 μm, the thickness is 5 μm, and the length is 45 μm.

6. The real-time liquid flow velocity monitoring sensor based on MEMS planar resonance technology according to claim 2, characterized in that, The diameter of the large arc edge at the front end of the sector-shaped sensing plate (2) is 95 μm, the diameter of the small arc edge is 45 μm, the thickness is 5 microns, and the surface area of the sector-shaped sensing plate (2) is 905 μm 2 0.

7. The real-time liquid flow velocity monitoring sensor based on MEMS planar resonance technology according to claim 1, wherein The parameters of the electrothermal resonance excitation thin beam (3) and the piezoresistive frequency readout thin beam (4) are both width 2 μm, length 20 μm, and thickness 5 μm.

8. A method for measuring the liquid flow rate by changing the resonance frequency of the sensor according to any one of claims 1-7 using liquid pressure, characterized in that, An alternating magnetic field is applied to the electrothermal resonance excitation thin beam (3) to make the magnetic sensor generate an in-plane torsional pendulum mode resonance. Utilizing the deflection effect generated by the sensor affected by the flow velocity in a fluid environment, when the fluid flows through the sensor, the pressure generated by the flow velocity causes the sensor to deflect. During the flow velocity measurement, the deflection of the sensor causes a shift in its in-plane torsional pendulum resonance frequency. Through the pre-calibrated flow velocity-frequency relationship, the flow velocity of the fluid is inversely deduced from the measured frequency change to achieve high-precision flow velocity monitoring.

9. The method for measuring the liquid flow rate according to the resonant frequency of the sensor as claimed in claim 8, wherein The specific content is as follows: Step 1: Connect the electrothermal resonance excitation thin beam (3) to the drive circuit, and connect the piezoresistive frequency readout thin beam (4) to the readout circuit. Apply a 2.5 V alternating current superimposed with a 2 V DC bias voltage to the electrothermal excitation resistor of the electrothermal resonance excitation thin beam (3) through the drive circuit, and obtain the resonance frequency of the sector-shaped sensing plate (2) through the readout circuit connected to the piezoresistive frequency readout thin beam (4). Step 2: Calibrate the sensitivity of the sensor Treat the surface of the entire sensor with PEG-silane at 75 °C for 90 minutes, and then rinse the sensor with ethanol and deionized water in sequence to remove surface impurities. Immerse the surface-treated sensor in a liquid environment identical to the liquid to be measured. Apply an alternating current of 2.5 V superimposed with a direct current bias voltage of 2 V to the electrothermal resonance excitation fine beam (3) through a drive circuit, causing the sector-shaped sensing plate (2) to resonate in the in-plane mode. Then, vary the velocity of the liquid from 0 to different known flow velocities and record the resonance frequencies of the sector-shaped sensing plate (2) at different liquid flow velocities. Plot a curve with the liquid flow velocity as the abscissa and the resonance frequency of the sector-shaped sensing plate (2) as the ordinate to obtain a sensitivity calibration curve as the calibrated flow velocity-frequency relationship; Step 3: Place the calibrated sensor in the liquid with the flow velocity to be measured and record the resonance frequency generated in real time; Step 4: According to the resonance frequency of the sensor, refer to the calibrated sensitivity curve to obtain the real-time result of the flow velocity of the liquid to be measured.

10. A method for preparing a real-time liquid flow rate monitoring sensor based on MEMS planar resonance technology according to any one of claims 1-7, characterized in that, The specific content is as follows: Step 1: Substrate pretreatment Cleaning and activation: Take a 5-inch SOI substrate, place it in a mixed solution of acetone and isopropyl alcohol, and ultrasonically clean it for 10 minutes; then perform oxygen plasma activation treatment for 5 minutes, and finally bake the substrate in a high-temperature furnace at 120 °C for 10 minutes to completely remove residual moisture and gas; Thermal oxidation growth of the oxide layer: Use a dry-wet process to grow a silicon dioxide layer on the pretreated substrate to obtain a sample; first place the substrate in an environment of 1000 °C, perform dry oxygen treatment for 10 minutes to form an initial oxide layer, then perform wet oxygen treatment for 20 minutes to accelerate the oxidation process and allow silicon atoms to fully react with oxygen, ultimately generating a dense amorphous silicon dioxide layer with a thickness of 200 nm; Step 2: Basic structure processing Lithography and ion implantation: Adsorb the sample on a spin-coating tray, spin-coat a suitable photoresist to form a uniform photoresist layer, and bake it on a hot plate at 95 °C for 90 seconds to cure it; use a lithography machine equipped with a mask template with specific ion implantation feature patterns for contact exposure, control the ultraviolet light irradiation for 270 milliseconds, and form a latent image of the ion implantation area in the photoresist layer; After exposure, the sample was immersed in a 2.38% TMAH developer for 40 seconds to dissolve the unexposed photoresist and achieve pattern transfer; then it was baked on a hot plate at 100 °C for 2 minutes; using an RIE device, the etching power was set to 120 W, the CHF3 gas flow rate was 30 sccm, and the etching time was 5 minutes to etch through a 200-nm silicon dioxide layer to open a channel for ion implantation; then boron ion implantation was carried out with a dose of 1E15 / cm 3 , an energy of 75 keV, and the photoresist was removed after implantation; Front-side structure etching and annealing: Spin-coat and cure photoresist on the sample after the above treatment again, use a mask template of the front-side structure features of the sensor for lithography, perform contact exposure for 270 milliseconds and then develop it, bake it on a hot plate at 100 °C for 2 minutes after development, use a deep silicon etching device, use a mixed gas of SF6 and C4F8 as the etching gas, with an SF6 flow rate of 100 - 200 sccm, a C4F8 flow rate of 20 - 50 sccm, an etching power of 500 - 800 W, an etching depth of 5 um, and a minimum line width of 4 um, etch through the 5-um-thick silicon dioxide layer to form the front-side structure, and remove the photoresist after etching; finally, place the sample in a dry oxygen and wet oxygen environment at 1000 °C and oxidize it for 10 minutes and 20 minutes respectively; then use an RIE device to remove the excess silicon dioxide layer; Step 3: Fabrication of the functional layer Electrode fabrication: Spin-coat and cure photoresist on the substrate, use a mask template of the metal lift-off feature patterns to spin-coat the entire surface with photoresist but do not expose it for the time being; By means of magnetron sputtering technology, a 20-nm-thick Cr and a 300-nm-thick Au are deposited on the substrate surface in accordance with the designed area to form the lead (5) and the electrode (6) structures; then a lift-off operation is performed to remove the excess sputtered material and retain the required electrode (6) pattern; the sample is annealed at 425 °C for 30 minutes; Insulating layer preparation: A 500-nm-thick SiO2 insulating layer is deposited on the substrate surface by using a PECVD device to cover the lead (5); after the deposition is completed, photoresist is spin-coated and cured, and the whole surface is evenly coated with the photoresist using the insulating layer feature pattern mask. Then, using an RIE device, the etching power is set to 180 W, the CHF3 gas flow rate is 50 sccm, and the etching time is 9 minutes to etch the 500-nm-thick SiO2 insulating layer to form the required insulating layer pattern. After the etching is completed, the photoresist is removed; Step Four: Device post-processing Backside processing and structure release: Photoresist is spin-coated and cured on the backside of the substrate, and lithography is performed using the sensor back cavity etching feature pattern mask. The exposure method and time are determined according to the actual process, and development is carried out after exposure; After development, it is baked on a hot plate at 100 °C for 2 minutes; A deep silicon etching device is used to etch the substrate silicon by 400 μm to form a back cavity structure. After the etching is completed, the photoresist is removed; the sample is placed in an HF solution to release a 0.5-μm-thick buried oxide layer; Cutting and forming: Using a laser stealth cutting device, the processed substrate is cut according to the predetermined size to complete the fabrication of the sensor.

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