Multi-driving-mode micro-cantilever plate array MEMS viscosity sensor chip and working method thereof

Abstract

The invention belongs to the technical field of MEMS (micro-electromechanical systems) sensors, and discloses a multi-drive-mode micro-cantilever plate array MEMS viscosity sensor chip and a working method thereof. A silicon-based clamped body is connected with a first step micro-cantilever plate array suspension structure and a second step micro-cantilever plate array suspension structure; each of the first-step micro-cantilever plate array suspension structure and the second-step micro-cantilever plate array suspension structure comprises a rectangular supporting plate and a wide plate cantilever which are coaxially arranged, the two ends of the supporting plate are connected with the silicon-based clamped support body and the wide plate cantilever respectively, and the width of the supporting plate is smaller than that of the wide plate cantilever; a metal layer coil is arranged on the surface of the wide plate cantilever; piezoelectric electrode pairs are symmetrically arranged on the supporting plate, and each electrode is connected with a metal lead. A rigidity connecting beam is connected between the two supporting plates, the two supporting plates are the same in size, and the length and the width of the first wide plate cantilever are smaller than or equal to the length and the width of the second wide plate cantilever respectively. The vibration characteristic of the viscosity sensor immersed in the viscous fluid is improved, so that the viscosity measurement precision and stability of the viscosity sensor are improved.

Description

Technical Field

[0001] The present invention belongs to the field of MEMS (Micro Electromechanical Systems) sensors, and in particular relates to a multi-driving mode micro-cantilever plate array MEMS viscosity sensor chip and a working method thereof. Background Art

[0002] Viscosity is one of the important thermophysical parameters of fluids, and is also the basic data for scientific research such as thermophysical properties and fluid mechanics, and engineering applications such as energy and power, industrial control, etc. At present, in industrial sites and laboratories, traditional viscometers such as the capillary method are mainly used to obtain fluid viscosity data, that is, samples are taken first and then offline measurements are taken. However, during the operation of power systems such as internal combustion engines, it is necessary to monitor the viscosity parameters of working fluids such as engine oil and fuel in real time to ensure the normal and efficient operation of the power system. The rapid rise of MEMS resonant sensors is mainly due to the development of micromachining technology. Viscosity sensors based on MEMS technology have the advantages of small size, light weight, fast response, and low power consumption, making this type of sensor a feasible solution for achieving high-precision online measurement of fluid viscosity. However, existing MEMS viscosity sensors generally have problems such as low quality factor, insufficient liquid phase environment vibration driving force, and small vibration amplitude, which have become important factors restricting the improvement of the accuracy of fluid viscosity measurement. Therefore, it is necessary to optimize the sensor design from aspects such as sensor structural parameters, vibration mode design, and viscosity measurement methods, so as to provide design methods and technical basis for improving the comprehensive performance of MEMS viscosity sensors such as measurement accuracy and stability. 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 multi-drive mode micro-cantilever plate array MEMS viscosity sensor chip and a working method thereof, in order to improve the vibration characteristics of the viscosity sensor immersed in a viscous fluid, thereby improving its viscosity measurement accuracy and stability.

[0004] In order to achieve the above object, the present invention adopts the following technical solution: A multi-drive mode micro-cantilever plate array MEMS viscosity sensor chip comprises a silicon-based fixed support body, a first-step micro-cantilever plate array suspended structure and a second-step micro-cantilever plate array suspended structure are connected to the silicon-based fixed support body, the first-step micro-cantilever plate array suspended structure and the second-step micro-cantilever plate array suspended structure both comprise a rectangular and coaxially arranged support plate and a 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, the width of the support plate is smaller than the width of the wide plate cantilever; a metal layer coil is arranged on the surface of the wide plate cantilever; a piezoelectric electrode is arranged on the support plate The two electrodes in the piezoelectric electrode pair are symmetrically arranged about the symmetry axis in the length direction of the support plate, and each electrode is connected to a metal lead; a rigidity connecting beam is connected between the support plates of the first-step micro-cantilever plate array suspension structure and the second-step micro-cantilever plate array suspension structure, the support plates of the first-step micro-cantilever plate array suspension structure and the second-step micro-cantilever plate array suspension structure are the same in size, and the length and width of the wide plate cantilever of the first-step micro-cantilever plate array suspension structure are respectively less than and equal to the length and width of the wide plate cantilever of the second-step micro-cantilever plate array suspension structure.

[0005] Preferably, the metal layer coil is in a comb-teeth shape, and the teeth of the metal layer coil face the free end of the wide plate cantilever.

[0006] 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.

[0007] Preferably, the size of the metal layer coil on the wide plate cantilever of the first step micro-cantilever plate array suspended structure is the same as the size of the metal layer coil on the second step micro-cantilever plate array suspended structure.

[0008] Preferably, the stiffness connecting beam is Y-shaped, including a first thin beam, a second thin beam and a third thin beam, one end of the first thin beam is connected to the support plate of the first step micro-cantilever plate array suspended structure, the other end of the first thin beam is connected to the second thin beam and one end of the third thin beam, and the other end of the second thin beam and the third thin beam is connected to the support plate of the second step micro-cantilever plate array suspended structure.

[0009] Preferably, the electrodes in the piezoelectric electrode pair are rectangular in shape, and all electrodes have the same length, width and thickness; the length of the electrode is the same as the length of the support plate.

[0010] 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 52% to 57% 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, the wide plate cantilever and the stiffness connecting beam are the same.

[0011] 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; the width of the wide plate cantilever is greater than or equal to the length.

[0012] Preferably, the silicon-based solid support comprises a single crystal silicon substrate, the top surface of the single crystal silicon substrate is covered with a thermally oxidized silicon dioxide film, a piezoelectric layer bottom electrode molybdenum film is provided on the surface of the thermally oxidized silicon dioxide film, an aluminum nitride piezoelectric film is provided on the surface of the piezoelectric layer bottom electrode molybdenum film, a metal film for forming a piezoelectric electrode pair, a metal layer coil and a metal lead is provided on the surface of the aluminum nitride piezoelectric film, and the top surfaces of the aluminum nitride piezoelectric film and the metal film are covered with a PECVD silicon oxide 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, metal film, aluminum nitride piezoelectric film, piezoelectric layer bottom electrode molybdenum film, thermally 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 working method of the multi-driving mode micro-cantilever plate array MEMS viscosity sensor chip of the present invention as described above comprises: By means of a piezoelectric electrode pair arranged on a support plate and a metal layer coil arranged on a wide plate cantilever, a piezoelectric excitation and an electromagnetic excitation are coordinated to excite the first-step micro-cantilever plate array suspended structure and the second-step micro-cantilever plate array suspended structure to generate a localized vibration mode of a high-order bending mode. When the localized vibration mode of the high-order bending mode occurs, the first-step micro-cantilever plate array suspended structure has a significant bending vibration mode along the length and width directions, and the support plate of the first-step micro-cantilever plate array suspended structure has a bending vibration mode along the length direction. At this time, the high-order bending vibration of the second-step micro-cantilever plate array suspended structure is suppressed. A sinusoidal alternating voltage is applied to the driving electrodes in the same direction along the width of the support plate in each piezoelectric electrode pair, and the top electrode of the support plate is energized and the bottom electrode is grounded. All the support plates drive the wide plate cantilevers connected to them to vibrate under the action of the inverse piezoelectric effect. At the same time, the first-step micro-cantilever plate array suspended structure and the second-step micro-cantilever plate array suspended structure are placed in a constant magnetic field, and when bending vibration is generated in the constant magnetic field, a sinusoidal alternating voltage is applied to the metal layer coil arranged on the wide plate cantilever, and a Lorentz force is generated on the wide plate cantilever, driving the wide plate cantilever and the first-step micro-cantilever plate array suspended structure and the second-step micro-cantilever plate array suspended structure to generate a high-order bending vibration mode; When the frequency of the sinusoidal alternating voltage is the same as the localized natural frequency of the high-order bending modes of the first-step micro-cantilever plate array suspended structure and the second-step micro-cantilever plate array suspended structure, localized resonant vibration of the high-order bending modes is generated on the support plate and the wide plate cantilever of the first-step micro-cantilever plate array suspended structure, and the vibration of the support plate of the first-step micro-cantilever plate array suspended structure causes another electrode on the support plate to generate and output an alternating voltage detection signal due to the piezoelectric effect.

[0014] The present invention has the following beneficial effects: The multi-drive mode micro-cantilever plate array MEMS viscosity sensor chip of the present invention adopts a cooperative drive mode of piezoelectric excitation and electromagnetic excitation to excite the suspended structure of the step micro-cantilever plate array to generate bending vibration. Compared with the single drive mode of the traditional viscosity sensor, the multi-drive mode can significantly improve the vibration driving force of the sensor chip immersed in the viscous liquid, thereby improving the vibration stability and measurement accuracy; the metal layer coil arranged on the wide plate cantilever is used to generate an electromagnetic excitation force of a high-order bending vibration mode on the wide plate cantilever, which can excite the vibration along the length of the wide plate cantilever. , and provide targeted modal drive for the bending vibration mode in the width direction to ensure the vibration stability of the high-order bending vibration mode; adopt a stepped micro-cantilever plate array suspension structure, and stimulate the localization of the vibration mode of the stepped micro-cantilever plate array suspension structure through the difference design of the length of the two wide plate cantilevers. At the same time, the connecting beam adopts a Y-shaped structure design to further enhance the vibration energy of the stepped micro-cantilever plate array suspension structure on the basis of the localization of the vibration mode. The energy is transferred to a specific stepped micro-cantilever plate, thereby significantly improving the vibration characteristics such as the quality factor of the stepped micro-cantilever plate. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the description of the embodiments will be briefly introduced below. 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.

[0016] Figure 1Schematic diagram of the overall structure of a multi-drive mode micro-cantilever plate array MEMS viscosity sensor chip according to an embodiment of the present invention.

[0017] Figure 2 for Figure 1 Schematic diagram of the cross section along A-A'.

[0018] Figure 3 It is a simulation diagram of the localized bending vibration of the suspended array structure of the stepped micro-cantilever plate in the working mode in the embodiment of the present invention.

[0019] Figure 4 It is a simulation diagram of the bending vibration mode of the suspended array structure of the stepped micro-cantilever plate in the embodiment of the present invention.

[0020] 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-rigidity connecting beam, 5-1-first thin beam, 5-2-second thin beam, 5-3-third thin beam, 6-metal layer coil, 6-1-raised portion, 6-2-groove, 7-silicon-based solid support, 8-metal lead, 9-single crystal silicon substrate, 10-thermal oxide silicon film, 11-piezoelectric bottom electrode molybdenum film, 12-low stress aluminum nitride piezoelectric film, 13-metal layer film, 14-PECVD silicon oxide film (i.e., plasma enhanced chemical vapor deposition silicon oxide film), 15-first step micro-cantilever plate array suspended structure, 16-second step micro-cantilever plate array suspended structure. DETAILED DESCRIPTION

[0021] 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.

[0022] Reference Figure 1The multi-drive mode micro-cantilever plate array MEMS viscosity sensor chip of this embodiment includes a silicon-based fixed support body 7, and two step micro-cantilever plate array suspension structures are connected to the silicon-based fixed support body 7. The step micro-cantilever plate array suspension structure includes a support plate connected to the fixed 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. The piezoelectric electrode pair serves as the top electrode of the support plate, and a stiffness connecting beam 5 is connected between adjacent support plates; specifically, the two step micro-cantilever plate array suspension structures are respectively recorded as a first step micro-cantilever plate array suspension structure 15 and a second step micro-cantilever plate array suspension structure 16. Among them, the first step micro-cantilever plate array suspended structure 15 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 7, 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 16 includes a rectangular 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, one end of the second support plate 3-2 is connected to the silicon-based fixed support body 7, and the other end of the second support plate 3-2 is connected to the second wide plate The cantilever 2 is connected; 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 symmetry axis of the wide side of the first support plate 3-1 is parallel to the symmetry axis of the wide side of the second support plate 3-2, the width of the first wide plate cantilever 1 and the second wide plate cantilever 2 are the same, the length of the second wide plate cantilever 2 is greater than the first wide plate cantilever 1, and a gap is left between the first wide plate cantilever 1 and the second wide plate cantilever 2; wherein, the length of the first wide plate cantilever 1 is less than the length of the second wide plate cantilever 7; the thickness of the first wide plate cantilever 1 is the same as the thickness of the second wide plate cantilever 2, and the width of the first wide plate cantilever 1 is the same as the width of the second wide plate cantilever 2; the thickness of the stepped micro-cantilever plate array suspended structure is less than 5 times or more of the length and width of the support plate, and is also less than 5 times or more of the length and width of the wide plate cantilever. That is to say, 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.Metal layer coils 6 are arranged on the surfaces of the first wide plate cantilever 1 and the second wide plate cantilever 2, and the metal layer coils on the first wide plate cantilever 1 and the metal layer coils on the second wide plate cantilever 2 have the same shape and size; the metal layer coils are arranged in a rectangular concave-convex shape (similar to a comb shape), specifically, the metal layer coils have rectangular, alternatingly distributed protrusions 6-1 and grooves 6-2, the ends of the protrusions 6-1 and the openings of the grooves 6-2 face the free ends of the first wide plate cantilever 1 or the second wide plate cantilever 2, the number of the protrusions 6-1 is an even number, and the number of the grooves 6-2 is an odd number, the metal layer coils are symmetrically arranged along the symmetry axis of the length direction of the first wide plate cantilever 1 or the second wide plate cantilever 2, and the edges on both sides of the metal layer coils are set as protrusions 6-1; a first piezoelectric electrode pair 4-1 is provided on the first support plate 3-1, and the first piezoelectric electrode The two electrodes in the 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, the two electrodes in the second piezoelectric electrode pair 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.

[0023] The rigidity connecting beam 5 is connected between the first support plate 3-1 and the second support plate 3-2. The thickness of the rigidity connecting beam 5, the thickness of the first support plate 3-1, the first wide plate cantilever 1, the second support plate 3-2 and the second wide plate cantilever 2 are the same. The rigidity connecting beam 5 is in a Y shape. The rigidity connecting beam 5 is connected to the second support plate 3-2 by a double thin beam and to the first support plate 3-1 by a single thin beam. Specifically, the Y-shaped rigidity connecting beam 5 includes a first thin beam 5-1, a second thin beam 5-2 and a third thin beam 5-3. -3, wherein one end of the first thin beam 5-1 is connected to the first support plate 3-1, the other end of the first thin beam 5-1 is connected to one end of the second thin beam 5-2 and the third thin beam 5-3, and the other ends of the second thin beam 5-2 and the third thin beam 5-3 are both connected to the second support plate 3-2; more preferably, the first thin beam 5-1, the second thin beam 5-2 and the third thin beam 5-3 have the same width, the first thin beam 5-1 and the second thin beam 5-2 are located on the same straight line, and the third thin beam 5-3 is at a certain angle to the second thin beam 5-2. Since the length of the second wide plate cantilever 2 is greater than that of the first wide plate cantilever 1, when a high-order bending vibration mode is generated, the vibration frequency of the second step micro-cantilever plate array suspended structure 16 is lower than the vibration frequency of the first step micro-cantilever plate array suspended structure 15, that is, the vibration energy of the second step micro-cantilever plate array suspended structure 16 is lower than that of the first step micro-cantilever plate array suspended structure 15. At the same time, through the design of the Y-shaped stiffness connecting beam 5, the transmission effect of the vibration energy from the second step micro-cantilever plate array suspended structure 16 to the first step micro-cantilever plate array suspended structure 15 can be enhanced, thereby improving the vibration characteristics of the first step micro-cantilever plate array suspended structure 15.

[0024] 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.

[0025] The working method of the multi-drive mode micro-cantilever plate array MEMS viscosity sensor chip according to the above embodiment of the present invention includes the following process: By means of the first piezoelectric electrode pair 4-1 arranged on the first support plate 3-1 and the metal layer coil 6 arranged on the first wide plate cantilever 1, as well as the second piezoelectric electrode pair 4-2 arranged on the second support plate 3-3 and the metal layer coil 6 arranged on the second wide plate cantilever 2, the first step micro-cantilever plate array suspended structure 15 and the second step micro-cantilever plate array suspended structure 16 are stimulated to produce localized vibration modes of high-order bending modes by coordinating piezoelectric excitation and electromagnetic excitation. When the localized vibration mode of high-order bending modes occurs, the first step micro-cantilever plate array suspended structure 15 has significant bending vibration modes along the length and width directions, and the first support plate 3-1 has a bending vibration mode along the length direction. At this time, the high-order bending vibration of the second step micro-cantilever plate array suspended structure 16 is suppressed.

[0026] A sinusoidal alternating voltage is applied to the driving electrodes in the same direction along the width of the support plate in each piezoelectric electrode pair, so that the top electrode is energized and the bottom electrode is grounded on the support plate. That is to say, a sinusoidal alternating voltage is applied to the driving electrodes in the same direction along the width of the first support plate 3-1 in the first piezoelectric electrode pair 4-1, so that the top electrode is energized and the bottom electrode is grounded on the first support plate 3-1; a sinusoidal alternating voltage is applied to the driving electrodes in the same direction along the width of the second support plate 3-2 in the second piezoelectric electrode pair 4-2, so that the top electrode is energized and the bottom electrode is grounded on the second support plate 3-2; all the support plates drive the wide plate cantilevers connected to them to vibrate under the action of the inverse piezoelectric effect, that is, 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 1 to vibrate under the action of the inverse piezoelectric effect. At the same time, when the stepped micro-cantilever plate suspended structure (including the first stepped micro-cantilever plate array suspended structure 15 and the second stepped micro-cantilever plate array suspended structure 16) is placed in a constant magnetic field and generates bending vibration in the constant magnetic field, a sinusoidal alternating voltage is applied to the metal layer coil 6 arranged on the wide plate cantilever (including the first wide plate cantilever 1 and the second wide plate cantilever 2), thereby generating a Lorentz force on the wide plate cantilever (including the first wide plate cantilever 1 and the second wide plate cantilever 2), driving the wide plate cantilever (including the first wide plate cantilever 1 and the second wide plate cantilever 2) and the overall stepped micro-cantilever plate suspended structure (the first stepped micro-cantilever plate array suspended structure 15 and the second stepped micro-cantilever plate array suspended structure 16) to generate high-order bending vibration modes. That is to say, when the first-step micro-cantilever plate suspended structure 15 is placed in a constant magnetic field and generates bending vibration in the constant magnetic field, a sinusoidal alternating voltage is passed through the metal layer coil 6 arranged on the first wide plate cantilever 1, thereby generating a Lorentz force on the first wide plate cantilever 1, driving the first wide plate cantilever 1 and the entire first-step micro-cantilever plate suspended structure 15 to generate high-order bending vibration modes; when the second-step micro-cantilever plate suspended structure 16 is placed in a constant magnetic field and generates bending vibration in the constant magnetic field, a sinusoidal alternating voltage is passed through the metal layer coil 6 arranged on the second wide plate cantilever 2, thereby generating a Lorentz force on the second wide plate cantilever 2, driving the second wide plate cantilever 2 and the entire second-step micro-cantilever plate suspended structure 16 to generate high-order bending vibration modes.

[0027] When the frequency of the sinusoidal alternating voltage is the same as the localized natural frequency of the high-order bending mode of the stepped micro-cantilever plate array suspended structure (including the first stepped micro-cantilever plate array suspended structure 15 and the second stepped micro-cantilever plate array suspended structure 16), high-order bending mode localized resonant vibration is generated on the first support plate 3-1 of the first stepped micro-cantilever plate array suspended structure 15 and the first wide plate cantilever 1, and the vibration of the first support plate 3-1 of the first micro-cantilever plate suspended structure 15 causes another piezoelectric electrode on the first support plate 3-1 to generate and output an alternating voltage detection signal due to the piezoelectric effect.

[0028] The sensor chip of the present invention adopts a stepped micro-cantilever plate array structure to excite the modal localization of high-order bending vibrations, thereby measuring the viscosity of the fluid. The micro-cantilever plate array under this mode produces an energy localization phenomenon, so that its overall vibration energy is transmitted to a single stepped micro-cantilever plate structure. At the same time, a high-order bending vibration mode is used as a working mode, thereby improving the vibration damping resistance of a specific micro-cantilever plate immersed in a viscous fluid.

[0029] In this embodiment, the size of the first wide plate cantilever 1 is: length × width = (550 ± 5) × (1000 ± 5) μm 2 , 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 dimensions of the first support plate 3-1 and the second support plate 3-2 are: length × width = (300±10) × (280±10) μm 2 , the thickness is 20±5μm; the thickness of the stiffness connecting beam 5 is 20±5μm, the length of the first thin beam 5-1 is 500±5μm, the length of the second thin beam 5-2 is 300±5μm, the angle between the third thin beam 5-3 and the second thin beam 5-2 is 6°, and the width of the first thin beam 5-1, the second thin beam 5-2 and the third thin beam 5-3 is 25±3μm.

[0030] like Figure 2As shown, in the cross-sectional view of the MEMS viscosity sensor chip of the stepped micro-cantilever plate array structure of the present embodiment, the sensor chip is prepared by a single crystal silicon substrate 9, and the upper and lower surfaces (i.e., the top surface and the back surface) of the single crystal silicon substrate 9 are covered with a thermally oxidized silicon dioxide film 10, and the thermally oxidized silicon dioxide film 10 is used as an insulating layer of the single crystal silicon substrate 9, and the thermally oxidized silicon dioxide film 10 on the bottom surface (i.e., the back surface) of the single crystal silicon substrate 9 is finally removed; the surface of the thermally oxidized silicon dioxide film 10 on the top surface of the single crystal silicon substrate 9 is provided with a piezoelectric layer bottom electrode molybdenum film 11, and the surface of the piezoelectric layer bottom electrode molybdenum film 11 is provided with an aluminum nitride piezoelectric film 12, and the piezoelectric layer bottom electrode molybdenum film 11 can be used as a chip bottom electrode It is grounded and can also serve as a substrate layer for the deposition of the aluminum nitride piezoelectric film 12; the piezoelectric film of the sensor chip adopts an aluminum nitride film to generate the inverse piezoelectric effect and the piezoelectric effect, so as to realize the excitation of the vibration mode and the detection of the electrical signal; a metal film 13 is provided on the surface of the aluminum nitride piezoelectric film 12, and the metal film 13 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 6 and a metal lead 8; a PECVD silicon oxide film 14 is provided on the top surface of the aluminum nitride piezoelectric film 12 and the metal film 13, and the PECVD silicon oxide film 14 covers the entire top surface of the sensor chip and is used for insulation in the fluid medium. Figure 2 The area on the left side where the single crystal silicon substrate 9 has a larger thickness represents the silicon-based solid support 7 of the sensor chip, and the area on the left side where the single crystal silicon substrate 9 has a smaller thickness represents the stepped micro-cantilever plate suspended structure. Specifically, the first stepped micro-cantilever plate array suspended structure 15 and the second stepped micro-cantilever plate array suspended structure 16 share the PECVD silicon oxide film 14, the metal film 13, the aluminum nitride piezoelectric film 12, the piezoelectric layer bottom electrode molybdenum film 11, the thermally oxidized silicon dioxide film 10 on the top surface of the single crystal silicon substrate 9, and part of the single crystal silicon substrate 9 (specifically, a part of the top of the single crystal silicon substrate 9) with the silicon-based solid support 7.

[0031] like Figure 3 and Figure 4 Comsol 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 viscous liquid, and the piezoelectric excitation force is 5 μN. Figure 3 is the simulation result of the localized high-order bending vibration mode of the first micro-cantilever plate. Figure 4 is the simulation result of the relationship between the vibration amplitude and fluid viscosity of the first microcantilever plate in the localized high-order bending vibration mode, where Figure 3 This is the working mode adopted by the viscosity 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 149270 Hz. Figure 4 In the present invention, liquids with different viscosity values, such as n-heptane, cyclohexane, MD2M and D4, are used for simulation analysis to obtain the relationship curve between the vibration of the suspended structure of the stepped micro-cantilever plate and the viscosity of the fluid. Then, the corresponding relationship between the vibration amplitude and the viscosity of the fluid can be established through the output vibration amplitude of the viscosity sensor chip, so as to verify the fluid viscosity measurement method proposed in the present invention.

[0032] In summary, the stepped micro-cantilever plate suspension structure in the present invention is covered with a low-stress aluminum nitride piezoelectric film and a metal layer coil. The micro-cantilever plate array structure is stimulated to produce localized high-order bending vibration modes by coordinating piezoelectric excitation with electromagnetic excitation. The Y-shaped stiffness connecting beam design is used to enhance the localization effect of the vibration mode of the overall stepped micro-cantilever plate suspension structure, thereby enhancing the vibration characteristics of the sensor chip in the viscous fluid. The resonant stress generated by the stepped micro-cantilever plate suspension structure can be converted into an electrical signal output through the piezoelectric effect. The viscosity sensor chip can improve the measurement accuracy of the fluid viscosity and has piezoelectric self-detection performance in the fluid.

[0033] It can be seen from the above scheme that the MEMS viscosity sensor chip based on the stepped micro-cantilever plate structure of the present invention has the advantages of simple structure, flexible modal driving mode and mature machine preparation process, and adopts high-order bending vibration mode to increase the vibration stiffness and enhance the fluid damping resistance of the sensor chip immersed in the viscous fluid, thereby improving the measurement performance of this type of sensor such as fluid viscosity measurement accuracy and stability.

[0034] 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 multi-drive mode micro-cantilever plate array MEMS viscosity sensor chip, characterized in that: The invention comprises a silicon-based fixed support body (7), a first-step micro-cantilever plate array suspended structure (15) and a second-step micro-cantilever plate array suspended structure (16) being connected to the silicon-based fixed support body (7), the first-step micro-cantilever plate array suspended structure (15) and the second-step micro-cantilever plate array suspended structure (16) both comprising a rectangular support plate and a wide plate cantilever arranged coaxially, the two ends of the support plate being respectively connected to the silicon-based fixed support body and the wide plate cantilever, the width of the support plate being smaller than the width of the wide plate cantilever; a metal layer coil (6) being arranged on the surface of the wide plate cantilever; a piezoelectric electrode pair being arranged on the support plate, the two electrodes of the piezoelectric electrode pair being in contact with each other. The support plates are arranged symmetrically about an axis of symmetry in the length direction, and each electrode is connected to a metal lead (8); a rigidity connecting beam (5) is connected between the support plates of the first-step micro-cantilever plate array suspended structure (15) and the second-step micro-cantilever plate array suspended structure (16); the support plates of the first-step micro-cantilever plate array suspended structure (15) and the second-step micro-cantilever plate array suspended structure (16) are of the same size; and the length and width of the wide plate cantilever of the first-step micro-cantilever plate array suspended structure (15) are respectively less than and equal to the length and width of the wide plate cantilever of the second-step micro-cantilever plate array suspended structure (16).

2. The multi-drive mode micro-cantilever plate array MEMS viscosity sensor chip according to claim 1, characterized in that: The metal layer coil (6) is in the shape of comb teeth, with the teeth of the metal layer coil (6) facing the free end of the wide plate cantilever.

3. The multi-drive mode micro-cantilever plate array MEMS viscosity sensor chip according to claim 2, characterized in that: The teeth of the metal layer coil (6) include rectangular raised portions (6-1) and grooves (6-2) that are alternately distributed, the ends of the raised portions (6-1) and the openings of the grooves (6-2) face the free ends of the wide plate cantilever, the number of the raised portions (6-1) is an even number, and the number of the grooves (6-2) is an odd number, the metal layer coil (6) is symmetrically arranged along the length direction of the wide plate cantilever, and the edges on both sides of the metal layer coil (6) are both provided as raised portions (6-1).

4. A multi-drive mode micro-cantilever plate array MEMS viscosity sensor chip according to any one of claims 1 to 3, characterized in that: The size of the metal layer coil (6) on the wide plate cantilever of the first stepped micro-cantilever plate array suspended structure (15) is the same as the size of the metal layer coil (6) on the second stepped micro-cantilever plate array suspended structure (16).

5. The multi-drive mode micro-cantilever plate array MEMS viscosity sensor chip according to claim 1, characterized in that: The stiffness connecting beam (5) is Y-shaped and comprises a first thin beam (5-1), a second thin beam (5-2) and a third thin beam (5-3); one end of the first thin beam (5-1) is connected to a support plate of a first step micro-cantilever plate array suspended structure (15); the other end of the first thin beam (5-1) is connected to the second thin beam (5-2) and one end of the third thin beam (5-3); the other ends of the second thin beam (5-2) and the third thin beam (5-3) are connected to a support plate of a second step micro-cantilever plate array suspended structure (16).

6. The multi-drive mode micro-cantilever plate array MEMS viscosity sensor chip according to claim 1, characterized in that: The electrodes in the piezoelectric electrode pair are rectangular in shape, and all electrodes have the same length, width and thickness; the length of the electrode is the same as the length of the support plate.

7. The multi-drive mode micro-cantilever plate array MEMS viscosity sensor chip according to claim 1, characterized in that: In the first-step micro-cantilever plate array suspended structure (15) and the second-step micro-cantilever plate array suspended structure (16), the length of the support plate is 52% to 57% 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, the wide plate cantilever and the stiffness connecting beam (5) are the same.

8. The multi-drive mode micro-cantilever plate array MEMS viscosity sensor chip 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; the width of the wide plate cantilever is greater than or equal to the length.

9. The multi-drive mode micro-cantilever plate array MEMS viscosity sensor chip according to claim 1, characterized in that: The silicon-based solid support (7) comprises a single crystal silicon substrate (9), the top surface of the single crystal silicon substrate (9) is covered with a thermally oxidized silicon dioxide film (10), a piezoelectric layer bottom electrode molybdenum film (11) is provided on the surface of the thermally oxidized silicon dioxide film (10), an aluminum nitride piezoelectric film (12) is provided on the surface of the piezoelectric layer bottom electrode molybdenum film (11), a metal film (13) used for forming a piezoelectric electrode pair, a metal layer coil (6) and a metal lead (8) is provided on the surface of the aluminum nitride piezoelectric film (12), and the top surfaces of the aluminum nitride piezoelectric film (12) and the metal film (13) are covered with PECVD oxygen The first-step micro-cantilever plate array suspended structure (15) and the second-step micro-cantilever plate array suspended structure (16) share the PECVD silicon oxide film (14), the metal film (13), the aluminum nitride piezoelectric film (12), the piezoelectric layer bottom electrode molybdenum film (11), the thermally oxidized silicon dioxide film (10) and part of the single crystal silicon substrate (9) with the silicon-based solid support (7), 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 operating method of a multi-drive mode micro-cantilever plate array MEMS viscosity sensor chip according to any one of claims 1 to 9, characterized in that: include: By means of a piezoelectric electrode pair arranged on a support plate and a metal layer coil (6) arranged on a wide plate cantilever, a piezoelectric excitation and an electromagnetic excitation are coordinated to excite the first step micro-cantilever plate array suspended structure (15) and the second step micro-cantilever plate array suspended structure (16) to generate a localized vibration mode of a high-order bending mode. When the localized vibration mode of the high-order bending mode occurs, the first step micro-cantilever plate array suspended structure (15) has a significant bending vibration mode along the length and width directions, and the support plate of the first step micro-cantilever plate array suspended structure (15) has a bending vibration mode along the length direction. At this time, the high-order bending vibration of the second step micro-cantilever plate array suspended structure (16) is suppressed; A sinusoidal alternating voltage is applied to the driving electrodes in the same direction along the width of the support plate in each piezoelectric electrode pair, and the top electrode of the support plate is energized and the bottom electrode is grounded. All the support plates drive the wide plate cantilevers connected to them to vibrate under the action of the inverse piezoelectric effect. At the same time, the first step micro-cantilever plate array suspended structure (15) and the second step micro-cantilever plate array suspended structure (16) are placed in a constant magnetic field and generate bending vibration in the constant magnetic field. A sinusoidal alternating voltage is applied to the metal layer coil (6) arranged in the wide plate cantilever, generating a Lorentz force on the wide plate cantilever, driving the wide plate cantilever and the first step micro-cantilever plate array suspended structure (15) and the second step micro-cantilever plate array suspended structure (16) to generate a high-order bending vibration mode. When the sinusoidal alternating voltage frequency is the same as the localized natural frequency of the high-order bending modes of the first-step micro-cantilever plate array suspended structure (15) and the second-step micro-cantilever plate array suspended structure (16), a localized resonant vibration of the high-order bending modes is generated on the support plate and the wide plate cantilever of the first-step micro-cantilever plate array suspended structure (15), and the vibration of the support plate of the first-step micro-cantilever plate array suspended structure (15) causes another electrode on the support plate to generate and output an alternating voltage detection signal due to the piezoelectric effect.

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