MEMS resonant sensor chip for measuring multiple parameters of fluid and working method of MEMS resonant sensor chip

Abstract

The invention belongs to the technical field of MEMS (micro-electromechanical system) sensors, and discloses an MEMS resonant sensor chip for fluid multi-parameter measurement and a working method of the MEMS resonant sensor chip. A first step micro-cantilever plate array suspension structure and a second step micro-cantilever plate array suspension structure which are the same in shape and size are connected onto a silicon-based clamped body; the first stepped micro-cantilever plate array suspension structure and the second stepped micro-cantilever plate array suspension structure each comprise a rectangular supporting plate and a wide plate cantilever which are coaxially arranged, symmetry axes on the wide edges of the two supporting plates are parallel, gaps are reserved between the adjacent edges of the wide plate cantilevers, the width of the supporting plates is smaller than that of the wide plate cantilevers, and the two ends of the supporting plates are connected with the silicon-based clamped support body and the wide plate cantilevers correspondingly. Piezoelectric electrode pairs are arranged on the supporting plate, and each piezoelectric electrode is connected with a metal lead. A comb-tooth-shaped metal layer coil is arranged on a wide plate cantilever of the first step micro-cantilever plate array suspension structure, and the tooth portion of the metal layer coil faces the free end of the wide plate cantilever. The sensor chip can realize cooperative measurement of different parameters of fluid, and has piezoelectric self-excitation and self-detection performance in the fluid.

Description

Technical Field

[0001] The present invention belongs to the technical field of MEMS (Micro Electromechanical Systems) sensors, and in particular relates to a MEMS resonant sensor chip for fluid multi-parameter measurement and a working method thereof. Background Art

[0002] The precise measurement of fluid parameters has broad application demands in the fields of energy, chemical engineering, healthcare, etc. Thanks to the development of micromachining technology, MEMS resonant sensors can realize micro-nanoscale structural design and mass production, and have the advantages of packaging integration, which can significantly reduce the manufacturing cost of sensors and meet the urgent needs of various fields for lightweight, fast response and real-time fluid measurement. Resonant sensors are frequency output sensors that can convert changes in fluid viscosity parameters into changes in frequency domain parameters under resonant state, such as resonant frequency, phase, etc., which also makes this type of sensor have good anti-interference ability and measurement accuracy. At present, most MEMS resonant sensors are only used for the measurement of a single specific fluid parameter. For the measurement of multiple fluid parameters, they have problems such as large output coupling error and low measurement accuracy, which reduces the efficiency of such sensors in fluid measurement and restricts the technical development of MEMS resonant sensors in the field of fluid measurement. Summary of the invention

[0003] In order to solve the problems existing in the prior art, the purpose of the present invention is to provide a MEMS resonant sensor chip for fluid multi-parameter measurement and a working method thereof, in order to improve the ability of the MEMS resonant sensor to measure fluid multi-parameters and its measurement performance.

[0004] In order to achieve the above object, the present invention adopts the following technical solution: A MEMS resonant sensor chip for multi-parameter measurement of fluid comprises a silicon-based fixed support body, to which a first-step micro-cantilever plate array suspended structure and a second-step micro-cantilever plate array suspended structure of the same shape and size are connected, the first-step micro-cantilever plate array suspended structure and the second-step micro-cantilever plate array suspended structure both comprise a rectangular support plate and a wide plate cantilever that are coaxially arranged, the symmetry axes on the wide sides of the two support plates are parallel, a gap is left between the adjacent edges of the two wide plate cantilevers, the width of the support plate is smaller than the width of the wide plate cantilever, the two ends of the support plate are respectively connected to the silicon-based fixed support body and the wide plate cantilever, a piezoelectric electrode pair is arranged on the support plate, the two piezoelectric electrodes of the piezoelectric electrode pair are symmetrically arranged on both sides of the symmetry axis of the wide side of the support plate, and each piezoelectric electrode is connected to a metal lead; a comb-tooth-shaped metal layer coil is provided on the wide plate cantilever of the first-step micro-cantilever plate array suspended structure, and the teeth of the metal layer coil face the free end of the wide plate cantilever.

[0005] Preferably: in the first-step micro-cantilever plate array suspended structure and the second-step micro-cantilever plate array suspended structure, the length of the support plate is 41% to 45% of the length of the wide plate cantilever, the width of the support plate is 26% to 30% of the width of the wide plate cantilever, and the thickness of the support plate is the same as the thickness of the wide plate cantilever.

[0006] Preferably, the length of the support plate is more than 5 times the thickness, and the width is more than 5 times the thickness; the length of the wide plate cantilever is more than 5 times the thickness, and the width is more than 5 times the thickness.

[0007] Preferably, the width of the wide plate cantilever is greater than or equal to its length.

[0008] Preferably, the support plate has a length of 290-310 μm, a width of 270-290 μm, and a thickness of 19-25 μm; the wide plate cantilever has a length of 695-705 μm, a width of 995-1005 μm, and a thickness of 19-25 μm.

[0009] Preferably, the two piezoelectric electrodes of the piezoelectric electrode pair are both rectangular in shape, and have the same length, width and thickness.

[0010] Preferably, the length of the two piezoelectric electrodes of the piezoelectric electrode pair is the same as the length of the support plate.

[0011] Preferably, the teeth of the metal layer coil include rectangular and alternatingly distributed protrusions and grooves, the ends of the protrusions and the openings of the grooves face the free end of the wide plate cantilever, the number of the protrusions is an even number, and the number of the grooves is an odd number, the metal layer coil is symmetrically arranged along the length direction of the wide plate cantilever, and the edges on both sides of the metal layer coil are set as protrusions.

[0012] Preferably, the silicon-based solid support includes a single crystal silicon substrate, a thermal oxidized silicon film is provided on the top surface of the single crystal silicon substrate, a piezoelectric layer bottom electrode molybdenum film is provided on the surface of the thermal oxidized silicon film, an aluminum nitride piezoelectric film is provided on the surface of the piezoelectric layer bottom electrode molybdenum film, a layer used to form a piezoelectric electrode pair, a metal layer coil, a metal lead and a metal film is provided on the surface of the aluminum nitride piezoelectric film, a PECVD silicon oxide film is provided on the top surfaces of the aluminum nitride piezoelectric film and the metal film, the first step micro-cantilever plate array suspended structure and the second step micro-cantilever plate array suspended structure share the PECVD silicon oxide film, the metal film, the aluminum nitride piezoelectric film, the piezoelectric layer bottom electrode molybdenum film, the thermal oxidized silicon dioxide film and part of the single crystal silicon substrate with the silicon-based solid support, wherein the thickness of the first step micro-cantilever plate array suspended structure and the second step micro-cantilever plate array suspended structure is less than the thickness of the silicon-based solid support.

[0013] The present invention also provides a working method of the MEMS resonant sensor chip for fluid multi-parameter measurement as described above, comprising: One of the piezoelectric electrodes in the piezoelectric electrode pair on the two support plates is used as a driving electrode of the vibration mode, the two driving electrodes are adjacent piezoelectric electrodes on the two support plates or piezoelectric electrodes far away from each other, the driving electrodes excite the first step micro-cantilever plate array suspended structure and the second step micro-cantilever plate array suspended structure to produce a torsional vibration mode with opposite vibration directions, and when a high-order torsional mode occurs, the first step micro-cantilever plate array suspended structure and the second step micro-cantilever plate array suspended structure both have torsional vibration modes in length and width directions; A sinusoidal alternating voltage is applied to the driving electrodes on the first-step micro-cantilever plate array suspended structure and the driving electrodes on the second-step micro-cantilever plate array suspended structure, so that the top electrode is energized and the bottom electrode is grounded on the support plate, and the support plate drives the respective connected wide plate cantilevers to vibrate under the action of the inverse piezoelectric effect; at the same time, a sinusoidal alternating voltage is applied to the metal layer coil to generate an alternating magnetic field around the metal layer coil, so that the first-step micro-cantilever plate array suspended structure generates a high-order torsional vibration mode and an alternating magnetic field, and the second-step micro-cantilever plate array suspended structure generates a high-order torsional mode opposite to the first-step micro-cantilever plate array suspended structure; The MEMS resonant sensor chip for multi-parameter measurement of fluid is placed in a fluid with ferromagnetic particles, the resonant frequency of the first-step micro-cantilever plate array suspended structure changes, and the second-step micro-cantilever plate array suspended structure resonates, and multi-parameter measurement of fluid density and ferromagnetic particle mass is performed through the synergistic effect of the first-step micro-cantilever plate array suspended structure and the second-step micro-cantilever plate array suspended structure; another piezoelectric electrode on the support plate is used to output an alternating voltage signal through the piezoelectric effect to collect the resonant frequency, and the output voltage signals of the first-step micro-cantilever plate array suspended structure and the second-step micro-cantilever plate array suspended structure are output as differential voltage signals.

[0014] The present invention has the following beneficial effects: The MEMS resonant sensor chip for multi-parameter measurement of fluid of the present invention adopts a dual array structure of step micro-cantilever plates, and excites the step micro-cantilever plates to generate high-order torsional vibration modes through the local arrangement of metal layer coils, and uses the resonant frequency as a key vibration parameter to achieve multi-parameter measurement of fluid density and the mass of ferromagnetic particles in the fluid; the dual array structure of the step micro-cantilever plates adopts reverse high-order torsional vibration modes, wherein the reverse vibrations of the two can constitute a differential output form of the sensor chip, so as to improve the output signal accuracy of the sensor chip; the use of high-order torsional vibration modes can improve the vibration frequency of the step micro-cantilever plate array structure and the contact area with the fluid, thereby improving the fluid parameter measurement sensitivity.

[0015] The MEMS resonant sensor chip for fluid multi-parameter measurement of the present invention realizes the excitation and detection of vibration modes by arranging piezoelectric electrode pairs, and does not require an external auxiliary excitation or vibration pickup module, which can increase the ease of operation of the sensor chip and improve the anti-interference ability and measurement accuracy of the sensor chip. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0017] Figure 1 This is a schematic diagram of the overall structure of a MEMS resonant sensor chip for fluid multi-parameter measurement according to an embodiment of the present invention.

[0018] Figure 2 for Figure 1 Schematic diagram of the cross section along A-A'.

[0019] Figure 3 It is a simulation diagram of the high-order torsional vibration of the suspended array structure of the stepped micro-cantilever plate in the working mode in the embodiment of the present invention.

[0020] Figure 4 It is a simulation diagram of the highly linear relationship between the resonant frequency and the fluid density of the stepped micro-cantilever plate suspended array structure in the high-order torsional vibration mode in the embodiment of the present invention.

[0021] In the figure, 1-first wide plate cantilever, 2-second wide plate cantilever, 3-1-first supporting plate, 3-2-second supporting plate, 4-1-first piezoelectric electrode pair, 4-2-second piezoelectric electrode pair, 5-metal layer coil, 5-1-raised portion, 5-2-groove, 6-silicon-based solid support, 7-metal lead, 8-single crystal silicon substrate, 9-thermal oxide silicon film, 10-piezoelectric bottom electrode molybdenum film, 11-low stress aluminum nitride piezoelectric film, 12-metal layer film, 13-PECVD silicon oxide film (i.e., plasma enhanced chemical vapor deposition silicon oxide film), 14-first step micro-cantilever plate array suspended structure, 15-second step micro-cantilever plate array suspended structure. DETAILED DESCRIPTION

[0022] In order to make the objectives, technical solutions and advantages of the present invention more clear, the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0023] Reference Figure 1The MEMS resonant sensor chip for multi-parameter measurement of fluid in this embodiment includes a silicon-based solid support body 6, and two step micro-cantilever plate array suspended structures are connected to the silicon-based solid support body 6. The step micro-cantilever plate array suspended structure includes a support plate connected to the solid support body at one end and a wide plate cantilever connected to the other end of the support plate. A piezoelectric electrode pair parallel to the length direction of the support plate is provided on the support plate, and the piezoelectric electrode pair serves as the top electrode of the support plate; specifically, the two step micro-cantilever plate array suspended structures are respectively recorded as a first step micro-cantilever plate array suspended structure 14 and a second step micro-cantilever plate array suspended structure 15. Among them, the first step micro-cantilever plate array suspended structure 14 includes a rectangular first support plate 3-1 and a first wide plate cantilever 1, the width of the first support plate 3-1 is less than the width of the first wide plate cantilever 1, the thickness of the first support plate 3-1 is equal to the thickness of the first wide plate cantilever 1, one end of the first support plate 3-1 is connected to the silicon-based fixed support body 6, and the other end of the first support plate 3-1 is connected to the first wide plate cantilever 1; the symmetry axis of the wide side of the first support plate 3-1 is coaxial with the symmetry axis of the wide side of the first wide plate cantilever 1; the second step micro-cantilever plate array suspended structure 15 includes a second support plate 3-2 and a second wide plate cantilever 2, the width of the second support plate 3-2 is less than the width of the second wide plate cantilever 2, the thickness of the second support plate 3-2 is equal to the thickness of the second wide plate cantilever 2, and one end of the second support plate 3-2 is connected to the silicon-based fixed support body 6 , the other end of the second support plate 3-2 is connected to the second wide plate cantilever 2; the symmetry axis of the wide side of the second support plate 3-2 is coaxial with the symmetry axis of the wide side of the second wide plate cantilever 2; the first support plate 3-1 and the second support plate 3-2 have the same length, width and thickness, the first wide plate cantilever 1 and the second wide plate cantilever 2 have the same length, width and thickness, the symmetry axis of the wide side of the first support plate 3-1 and the symmetry axis of the wide side of the second support plate 3-2 are parallel, and a gap is left between the first wide plate cantilever 1 and the second wide plate cantilever 2; the length and width of the first support plate 3-1 are both more than 5 times the thickness, the length and width of the first wide plate cantilever 1 are both more than 5 times the thickness, the length and width of the second support plate 3-2 are both more than 5 times the thickness, and the length and width of the second wide plate cantilever 2 are both more than 5 times the thickness.

[0024] A metal layer coil 5 is arranged on the surface of the first wide plate cantilever 1; the metal layer coil 5 is arranged in a rectangular concave-convex shape (similar to a comb shape), specifically, the metal layer coil 5 has rectangular, alternately distributed convex parts 5-1 and concave grooves 5-2, the ends of the convex parts 5-1 and the openings of the concave grooves 5-2 face the free end of the first wide plate cantilever 1, the number of the convex parts 5-1 is an even number, and the number of the concave grooves 5-2 is an odd number, the metal layer coil 5 is symmetrically arranged along the length direction of the first wide plate cantilever 1, and the edges on both sides of the metal layer coil 5 are set as convex parts 5-1; A first piezoelectric electrode pair 4-1 is provided on the first support plate 3-1, and the two electrodes in the first piezoelectric electrode pair are symmetrically arranged about the symmetry axis in the length direction of the first support plate 3-1, the length of the two electrodes in the first piezoelectric electrode pair 4-2 is equal to the length of the first support plate 3-1, and the width of the two electrodes in the first piezoelectric electrode pair 4-1 is equal; a second piezoelectric electrode pair 4-2 is provided on the second support plate 3-2, and the two electrodes in the second piezoelectric electrode pair 4-2 are symmetrically arranged about the symmetry axis in the length direction of the second support plate 3-2, the length of the two electrodes in the second piezoelectric electrode pair 4-2 is equal to the length of the second support plate 3-2, and the width of the two electrodes in the second piezoelectric electrode pair 4-2 is equal; the width of the two electrodes in the first piezoelectric electrode pair 4-1 is equal to the width of the two electrodes in the second piezoelectric electrode pair 4-2, and the two electrodes in the first piezoelectric electrode pair 4-1 and the two electrodes in the second piezoelectric electrode pair 4-2 are both connected with metal leads 8.

[0025] The length direction is along Figure 1 The X direction is parallel to the axis direction of the length direction of the wide plate cantilever, and the Y direction is the width direction, which is along the width direction of the wide plate cantilever.

[0026] The working method of the MEMS resonant sensor chip for fluid multi-parameter measurement according to the above embodiment of the present invention includes the following process: One of the piezoelectric electrodes in the piezoelectric electrode pair on the first support plate 3-1 and the second support plate 3-2 is used as a driving electrode of the vibration mode, and the two piezoelectric electrodes are piezoelectric electrodes on different sides of the support plate along the width direction. In this way, piezoelectric excitation is adopted to excite the first step micro-cantilever plate array suspended structure 14 and the second step micro-cantilever plate array suspended structure 15 to produce a torsional vibration mode with opposite vibration directions. When a high-order torsional mode occurs, the first step micro-cantilever plate array suspended structure 14 and the second step micro-cantilever plate array suspended structure 15 have torsional vibration modes in both the length and width directions. Specifically, Figure 1 To illustrate, the left piezoelectric electrode in the first piezoelectric electrode pair 4-1 on the first support plate 14 is used as the driving electrode of the vibration mode, and the right piezoelectric electrode in the second piezoelectric electrode pair 4-2 on the second support plate 15 is used as the driving electrode of the vibration mode, and the piezoelectric excitation method is used to excite the first step micro-cantilever plate array suspended structure 14 and the second step micro-cantilever plate array suspended structure 15 to produce a torsional vibration mode with opposite vibration directions. Similarly, the right piezoelectric electrode in the first piezoelectric electrode pair 4-1 on the first support plate 14 can be used as the driving electrode of the vibration mode, and the left piezoelectric electrode in the second piezoelectric electrode pair 4-2 on the second support plate 15 can be used as the driving electrode of the vibration mode, and the piezoelectric excitation method is used to excite the first step micro-cantilever plate array suspended structure 14 and the second step micro-cantilever plate array suspended structure 15 to produce a torsional vibration mode with opposite vibration directions.

[0027] A sinusoidal alternating voltage is applied to the driving electrodes on the first step micro-cantilever plate array suspended structure 14 and the driving electrodes on the second step micro-cantilever plate array suspended structure 15, and the top electrode of the first support plate 3-1 and the second support plate 3-2 are energized and the bottom electrode is grounded. The first support plate 3-1 and the second support plate 3-2 drive the respectively connected wide plate cantilevers to vibrate under the action of the inverse piezoelectric effect. That is to say, the first support plate 3-1 drives the first wide plate cantilever 1 to vibrate under the action of the inverse piezoelectric effect, and the second support plate 3-2 drives the second wide plate cantilever 2 to vibrate under the action of the inverse piezoelectric effect. At the same time, a sinusoidal alternating voltage is applied to the metal layer coil 5 on the first wide plate cantilever 1, an alternating current is generated in the metal layer coil 5, and an alternating magnetic field is further generated around the metal layer coil 5, so that the first step micro-cantilever plate array suspended structure 14 undergoes a high-order torsional vibration mode and generates an alternating magnetic field, and the second step micro-cantilever plate array suspended structure 15 undergoes a high-order torsional mode opposite to the first step micro-cantilever plate array suspended structure 14.

[0028] When the sensor chip is placed in a fluid with ferromagnetic particles, the first step micro-cantilever plate array suspended structure 14 will change its resonant frequency due to different fluid densities and the adsorption of the alternating magnetic field on the ferromagnetic particles. Since the second step micro-cantilever plate array suspended structure 15 is not provided with a metal layer coil 5, the change in the resonant frequency of the second step micro-cantilever plate array suspended structure 15 only reflects the change in fluid density. Therefore, through the synergistic effect of the first step micro-cantilever plate array suspended structure 14 and the second step micro-cantilever plate array suspended structure 15, multi-parameter measurement of fluid density and ferromagnetic particle mass can be performed. Another piezoelectric electrode on the first support plate 3-1 and the second support plate 3-2 is used to output an alternating voltage signal through the piezoelectric effect, thereby realizing the acquisition of the resonant frequency. The first step micro-cantilever plate array suspended structure 14 and the second step micro-cantilever plate array suspended structure 15 have opposite vibration directions, so that their output voltage signals are inverted, and can then be output as differential voltage signals, thereby reducing the interference of the external environment on the output signal of the sensor chip and improving the accuracy of the output signal of the sensor chip.

[0029] The sensor chip of the present invention adopts a stepped micro-cantilever plate array structure, and performs multi-parameter measurement of fluid density and fluid ferromagnetic particle mass through piezoelectric excitation assisted by locally arranged metal layer coils, providing a feasible design scheme for fluid quality assessment with fluid density and ferromagnetic particles as the main parameters. The stepped micro-cantilever plate array structure adopts a reverse vibration form to form a differential output voltage signal, thereby improving the output characteristics of the sensor chip.

[0030] In this embodiment, the size of the first wide plate cantilever 1 is: length × width = (700 ± 5) × (1000 ± 5) μm2 , thickness is 20±5μm; the size of the second wide plate cantilever 2 is: length × width = (700±5) × (1000±5) μm 2 , thickness is 20±5μm; the net distance between the first wide plate cantilever 1 and the second wide plate cantilever 2 is 100±5μm; the dimensions of the first support plate 3-1 and the second support plate 3-2 are: length × width = (300±10) × (280±10) μm 2 , thickness is 20±5μm; the size of the silicon-based support body 6 is: length × width = (700±5) × (1000±5) μm 2 , thickness is 100±5μm.

[0031] like Figure 2 As shown, in the cross-sectional view of the MEMS resonant sensor chip for fluid multi-parameter measurement of this embodiment, the sensor chip is prepared through a single crystal silicon substrate 8, and the upper and lower surfaces (i.e., the top surface and the back surface) of the single crystal silicon substrate 8 are covered with a thermal oxide silicon film 9, and the thermal oxide silicon film 9 is used as an insulating layer of the single crystal silicon substrate 8. The thermal oxide silicon film 9 on the bottom surface (i.e., the back surface) of the single crystal silicon substrate 8 is finally removed; a piezoelectric layer bottom electrode molybdenum film 10 is provided on the surface of the thermal oxide silicon film 9 on the top surface of the single crystal silicon substrate 8, and an aluminum nitride piezoelectric film 11 is provided on the surface of the piezoelectric layer bottom electrode molybdenum film 10, and the piezoelectric layer bottom electrode molybdenum film 10 can be used as a chip bottom electrode grounding, and can also be used as A substrate layer on which an aluminum nitride piezoelectric film 11 is deposited; the piezoelectric film of the sensor chip of the present invention adopts an aluminum nitride film, which is used to generate an inverse piezoelectric effect and a piezoelectric effect, and realize the excitation of vibration modes and the detection of electrical signals; a metal film 12 is provided on the surface of the aluminum nitride piezoelectric film 11, and the metal film 12 is used to form a piezoelectric electrode pair (including a first piezoelectric electrode pair 4-1 and a second piezoelectric electrode pair 4-2), a metal layer coil 5 and a metal lead 7; a PECVD silicon oxide film 13 is provided on the top surface of the aluminum nitride piezoelectric film 11 and the metal film 12, and the PECVD silicon oxide film 13 covers the entire surface of the sensor chip and is used to serve as an insulation in the fluid medium. Figure 2 The area on the left side where the single crystal silicon substrate 8 has a larger thickness represents the silicon-based solid support 6 of the sensor chip, and the area on the left side where the single crystal silicon substrate has a smaller thickness represents the stepped micro-cantilever plate suspended structure. Specifically, the first stepped micro-cantilever plate array suspended structure 14 and the second stepped micro-cantilever plate array suspended structure 15 share the PECVD silicon oxide film 13, metal film 12, aluminum nitride piezoelectric film 11, piezoelectric layer bottom electrode molybdenum film 10, thermal oxidation silicon dioxide film 9 on the top surface of the single crystal silicon substrate 8, and part of the single crystal silicon substrate 8 (specifically, a part of the top of the single crystal silicon substrate 8) with the silicon-based solid support 6.

[0032] like Figure 3 and Figure 4Comsol Multiphysics multi-physics field simulation software was used to perform fluid-solid coupling simulation analysis on the suspended array structure of the stepped micro-cantilever plate of the embodiment. n-heptane (density 684 kg / m 3 , viscosity is 0.4 cP) is the simulated fluid (liquid), and the piezoelectric excitation force is 10 μN. Figure 3 The simulation results of the high-order torsional vibration modes of the first and second step micro-cantilever plates with opposite vibration directions are shown in Figure 2. Figure 4 is the simulation result of the relationship between the vibration amplitude and fluid density of the first and second step micro-cantilever plates in the high-order torsional vibration mode, where Figure 3 This is the working mode adopted by the resonant sensor chip of the present invention. Figure 3 The resonant frequency of the stepped micro-cantilever plate suspended array structure obtained in the experiment is 131808 Hz. Figure 4 In the paper, different fluids (liquids) such as n-heptane, cyclohexane, MD2M and D4 were used for simulation analysis, and a highly linear relationship between the resonant frequency of the suspended array structure of the stepped micro-cantilever plate and the fluid density was obtained, thereby realizing the fluid density measurement.

[0033] In summary, the stepped micro-cantilever plate suspended structure in the present invention is covered with a low-stress aluminum nitride piezoelectric film to stimulate high-order torsional vibration modes through piezoelectric excitation. At the same time, a metal layer coil is arranged on one of the stepped micro-cantilever plate structures to achieve multi-parameter measurement of fluid density and ferromagnetic particle mass; the two stepped micro-cantilever plate structures adopt high-order torsional vibration modes with opposite vibration directions. When a high-order torsional vibration mode occurs, the stepped micro-cantilever plate suspended structure has torsional vibration modes in both length and width directions. Combined with reverse vibration, the vibration characteristics and output characteristics of the sensor chip can be improved.

[0034] It can be seen from the above scheme that the fluid multi-parameter measurement resonant sensor chip based on the stepped micro-cantilever plate structure of the present invention has the advantages of simple structure and preparation, convenient operation, etc., and adopts high-order torsional vibration modes of reverse vibration to constitute differential electrical signal output, and the high-order modes can increase the vibration stiffness to improve the fluid damping resistance of the sensor chip placed in the fluid, thereby improving the fluid measurement accuracy of this type of sensor on the basis of realizing multi-parameter measurement of the sensor chip.

[0035] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A MEMS resonant sensor chip for fluid multi-parameter measurement, characterized in that: The invention comprises a silicon-based fixed support body (6), to which a first-step micro-cantilever plate array suspended structure (14) and a second-step micro-cantilever plate array suspended structure (15) of the same shape and size are connected, wherein the first-step micro-cantilever plate array suspended structure (14) and the second-step micro-cantilever plate array suspended structure (15) both comprise a rectangular support plate and a wide plate cantilever that are coaxially arranged, wherein the symmetry axes on the wide sides of the two support plates are parallel, and a gap is left between the adjacent sides of the two wide plate cantilevers, and the support plate is provided with a plurality of support plates, wherein ... The width of the plate is smaller than the width of the wide plate cantilever, the two ends of the support plate are respectively connected to the silicon-based fixed support (6) and the wide plate cantilever, a piezoelectric electrode pair is provided on the support plate, the two piezoelectric electrodes of the piezoelectric electrode pair are symmetrically arranged on both sides of the symmetry axis of the wide side of the support plate, and each piezoelectric electrode is connected to a metal lead (7); a comb-tooth-shaped metal layer coil (5) is provided on the wide plate cantilever of the first-step micro-cantilever plate array suspended structure (14), and the teeth of the metal layer coil (5) face the free end of the wide plate cantilever.

2. The MEMS resonant sensor chip for fluid multi-parameter measurement according to claim 1, characterized in that: In the first-step micro-cantilever plate array suspended structure (14) and the second-step micro-cantilever plate array suspended structure (15), the length of the support plate is 41% to 45% of the length of the wide plate cantilever, the width of the support plate is 26% to 30% of the width of the wide plate cantilever, and the thickness of the support plate is the same as the thickness of the wide plate cantilever.

3. The MEMS resonant sensor chip for fluid multi-parameter measurement according to claim 1, characterized in that: The length of the support plate is more than 5 times the thickness, and the width is more than 5 times the thickness; the length of the wide plate cantilever is more than 5 times the thickness, and the width is more than 5 times the thickness.

4. The MEMS resonant sensor chip for fluid multi-parameter measurement according to claim 1, characterized in that: The width of the wide plate cantilever is greater than or equal to its length.

5. A MEMS resonant sensor chip for fluid multi-parameter measurement according to any one of claims 1 to 4, characterized in that: The length of the support plate is 290~310μm, the width is 270~290μm, and the thickness is 19~25μm; the length of the wide plate cantilever is 695~705μm, the width is 995~1005μm, and the thickness is 19~25μm.

6. The MEMS resonant sensor chip for fluid multi-parameter measurement according to claim 1, characterized in that: The two piezoelectric electrodes of the piezoelectric electrode pair are both rectangular in shape and have the same length, width and thickness.

7. A MEMS resonant sensor chip for fluid multi-parameter measurement according to claim 6, characterized in that: The lengths of the two piezoelectric electrodes of the piezoelectric electrode pair are the same as the length of the support plate.

8. The MEMS resonant sensor chip for fluid multi-parameter measurement according to claim 1, characterized in that: The teeth of the metal layer coil (5) include rectangular raised portions (5-1) and grooves (5-2) that are alternately distributed, the ends of the raised portions (5-1) and the openings of the grooves (5-2) facing the free end of the wide plate cantilever, the number of the raised portions (5-1) is an even number, the number of the grooves (5-2) is an odd number, the metal layer coil (5) is symmetrically arranged along the length direction of the wide plate cantilever, and the edges on both sides of the metal layer coil (5) are both provided as raised portions (5-1).

9. The MEMS resonant sensor chip for fluid multi-parameter measurement according to claim 1, characterized in that: The silicon-based solid support (6) comprises a single crystal silicon substrate (8), a thermally oxidized silicon film (9) is provided on the top surface of the single crystal silicon substrate (8), a piezoelectric layer bottom electrode molybdenum film (10) is provided on the surface of the thermally oxidized silicon film (9), an aluminum nitride piezoelectric film (11) is provided on the surface of the piezoelectric layer bottom electrode molybdenum film (10), a piezoelectric layer bottom electrode molybdenum film (10) is provided on the surface of the aluminum nitride piezoelectric film (11), a layer for forming a piezoelectric electrode pair, a metal layer coil (5) and a metal lead (7) and a metal film (12) is provided on the surface of the aluminum nitride piezoelectric film (11), and a PECVD silicon oxide film is provided on the top surfaces of the aluminum nitride piezoelectric film (11) and the metal film (12). The film (13), the first-step micro-cantilever plate array suspended structure (14) and the second-step micro-cantilever plate array suspended structure (15) share a PECVD silicon oxide film (13), a metal film (12), an aluminum nitride piezoelectric film (11), a piezoelectric layer bottom electrode molybdenum film (10), a thermally oxidized silicon dioxide film (9) and a portion of a single crystal silicon substrate (8) with the silicon-based solid support (6), wherein the thickness of the first-step micro-cantilever plate array suspended structure (14) and the second-step micro-cantilever plate array suspended structure (15) is less than the thickness of the silicon-based solid support (6).

10. The working method of a MEMS resonant sensor chip for fluid multi-parameter measurement according to any one of claims 1 to 9, characterized in that: include: One of the piezoelectric electrodes in the piezoelectric electrode pair on the two support plates is used as a driving electrode of the vibration mode, the two driving electrodes are adjacent piezoelectric electrodes on the two support plates or piezoelectric electrodes far away from each other, the driving electrodes excite the first step micro-cantilever plate array suspended structure (14) and the second step micro-cantilever plate array suspended structure (15) to generate a torsional vibration mode with opposite vibration directions, and when a high-order torsional mode occurs, the first step micro-cantilever plate array suspended structure (14) and the second step micro-cantilever plate array suspended structure (15) have a torsional vibration mode in both the length and width directions; A sinusoidal alternating voltage is applied to the driving electrodes on the first-step micro-cantilever plate array suspended structure (14) and the driving electrodes on the second-step micro-cantilever plate array suspended structure (15), so that the top electrode is energized and the bottom electrode is grounded on the support plate, and the support plate drives the respective connected wide plate cantilevers to vibrate under the action of the inverse piezoelectric effect; at the same time, a sinusoidal alternating voltage is applied to the metal layer coil (5), so that an alternating magnetic field is generated around the metal layer coil (5), so that the first-step micro-cantilever plate array suspended structure (14) generates a high-order torsional vibration mode and an alternating magnetic field, and the second-step micro-cantilever plate array suspended structure (15) generates a high-order torsional mode in the opposite direction to the first-step micro-cantilever plate array suspended structure (14); The MEMS resonant sensor chip for multi-parameter measurement of fluid is placed in a fluid containing ferromagnetic particles, the resonance frequency of the first-step micro-cantilever plate array suspended structure (14) changes, and the second-step micro-cantilever plate array suspended structure (15) resonates, and multi-parameter measurement of fluid density and ferromagnetic particle mass is performed through the synergistic effect of the first-step micro-cantilever plate array suspended structure (14) and the second-step micro-cantilever plate array suspended structure (15); another piezoelectric electrode on the support plate is used to output an alternating voltage signal through the piezoelectric effect to collect the resonance frequency, and the output voltage signals of the first-step micro-cantilever plate array suspended structure (14) and the second-step micro-cantilever plate array suspended structure (15) are output as differential voltage signals.

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