A multi-driving mode micro-cantilever array MEMS viscosity sensor chip and a working method thereof

Abstract

The application belongs to the technical field of MEMS sensor, and discloses a multi-drive mode micro-cantilever plate array MEMS viscosity sensor chip and a working method thereof. A first and a second stepped micro-cantilever plate array suspended structure are connected to a silicon-based fixed support body. The first and the second stepped micro-cantilever plate array suspended structure each comprises a support plate and a wide plate cantilever arranged in a rectangular and coaxial manner. The two ends of the support plate are connected to the silicon-based fixed support body and the wide plate cantilever, respectively. The width of the support plate is smaller than that of the wide plate cantilever. A metal layer coil is arranged on the surface of the wide plate cantilever. A piezoelectric electrode pair is symmetrically arranged on the support plate. Each electrode is connected to a metal lead wire. A stiffness connecting beam is connected between the two support plates. The two support plates are of the same size. The length and the width of the first wide plate cantilever are smaller than and equal to those of the second wide plate cantilever, respectively. The vibration characteristics of the viscosity sensor immersed in viscous fluid are improved, so that the viscosity measurement precision and stability are improved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of MEMS (Micro Electromechanical Systems) sensor, and particularly relates to a multi-drive mode micro cantilever array MEMS viscosity sensor chip and a working method thereof. BACKGROUND

[0002] Viscosity is one of the important thermophysical parameters of fluid, and is also a basic data for scientific research in thermophysics, fluid mechanics and engineering applications in energy power and industrial control. At present, in industrial field and laboratory, traditional viscometers such as capillary method are mainly used to obtain fluid viscosity data, that is, samples are taken and then measured offline, but in the running process of power systems such as internal combustion engine, the viscosity parameters of working medium such as engine oil and fuel need to be monitored in real time to ensure the normal and efficient operation of the power system. The rapid rise of MEMS resonant sensor is mainly due to the development of micro-machining technology, and the viscosity sensor based on MEMS technology has the advantages of small size, light weight, fast response and low power consumption, which provides a feasible solution for realizing high-precision online measurement of fluid viscosity. However, the existing MEMS viscosity sensor generally has the problems of low quality factor, insufficient liquid phase environment vibration driving force and small vibration amplitude, which become important factors restricting the improvement of the measurement precision of the viscosity sensor, so it is necessary to optimize the design of the sensor from the aspects of sensor structure parameters and vibration mode design, viscosity measurement method, etc., to provide design method and technical basis for improving the comprehensive performance of the MEMS viscosity sensor such as measurement precision and stability. SUMMARY

[0003] In order to solve the problems in the prior art, the purpose of the present application is to provide a multi-drive mode micro cantilever array MEMS viscosity sensor chip and a working method thereof, so as to improve the vibration characteristics of the viscosity sensor immersed in viscous fluid, and thus improve the viscosity measurement precision and stability.

[0004] In order to achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows:

[0005] The application discloses a multi-drive mode micro-cantilever array MEMS viscosity sensor chip, which comprises a silicon base fixed support body, a first ladder micro-cantilever array suspended structure and a second ladder micro-cantilever array suspended structure are connected to the silicon base fixed support body, the first ladder micro-cantilever array suspended structure and the second ladder micro-cantilever array suspended structure each comprise a support plate and a wide plate cantilever which are arranged coaxially in a rectangular shape, the two ends of the support plate are connected with the silicon base fixed support body and the wide plate cantilever respectively, and 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 pair is arranged on the support plate, the two electrodes in the piezoelectric electrode pair are symmetrically arranged about the symmetry axis of the length direction of the support plate, and each electrode is connected with a metal lead wire; a stiffness connecting beam is connected between the support plates of the first ladder micro-cantilever array suspended structure and the second ladder micro-cantilever array suspended structure, the sizes of the support plates of the first ladder micro-cantilever array suspended structure and the second ladder micro-cantilever array suspended structure are the same, the length and the width of the wide plate cantilever of the first ladder micro-cantilever array suspended structure are smaller than and equal to the length and the width of the wide plate cantilever of the second ladder micro-cantilever array suspended structure respectively.

[0006] Preferably, the metal layer coil is in a comb shape, and the tooth part of the metal layer coil faces the free end of the wide plate cantilever.

[0007] Preferably, the tooth part of the metal layer coil comprises rectangular and alternately distributed convex parts and grooves, the end part of the convex part and the opening of the groove face the free end of the wide plate cantilever, the number of the convex parts is even, the number of the grooves is odd, the metal layer coil is symmetrically arranged along the length direction of the wide plate cantilever, and the two side edges of the metal layer coil are provided as the convex parts.

[0008] Preferably, the size of the metal layer coil on the wide plate cantilever of the first ladder micro-cantilever array suspended structure is the same as the size of the metal layer coil on the second ladder micro-cantilever array suspended structure.

[0009] Preferably, the shape of the stiffness connecting beam is Y-shaped, and the stiffness connecting beam comprises a first thin beam, a second thin beam and a third thin beam, one end of the first thin beam is connected with the support plate of the first ladder micro-cantilever array suspended structure, the other end of the first thin beam is connected with one end of the second thin beam and the third thin beam, and the other ends of the second thin beam and the third thin beam are connected with the support plate of the second ladder micro-cantilever array suspended structure.

[0010] Preferably, the electrodes in the piezoelectric electrode pair are in a rectangular shape, and the length, the width and the thickness of all the electrodes are the same; the length of the electrode is the same as the length of the support plate.

[0011] Preferably, in the first and second stepped micro-cantilever array suspension structures, the length of the support plate is 52% to 57% of the length of the wide plate cantilever, and 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 link beam is the same.

[0012] Preferably, the length of the support plate is more than 5 times the thickness, and the width of the support plate is more than 5 times the thickness; the length of the wide plate cantilever is more than 5 times the thickness, and the width of the wide plate cantilever is more than 5 times the thickness; and the width of the wide plate cantilever is greater than or equal to the length.

[0013] Preferably, the silicon-based fixed support body comprises a monocrystalline silicon substrate, the top surface of the monocrystalline silicon substrate is covered with a thermal oxidation silicon dioxide film, the surface of the thermal oxidation silicon dioxide film is provided with a molybdenum film of a bottom electrode of a piezoelectric layer, the surface of the molybdenum film of the bottom electrode of the piezoelectric layer is provided with an aluminum nitride piezoelectric film, the surface of the aluminum nitride piezoelectric film is provided with a metal film used for forming a pair of piezoelectric electrodes, a metal layer coil and a metal lead, and the top surface of the aluminum nitride piezoelectric film and the metal film is covered with a PECVD silicon oxide film; the first and second stepped micro-cantilever array suspension structures share the PECVD silicon oxide film, the metal film, the aluminum nitride piezoelectric film, the molybdenum film of the bottom electrode of the piezoelectric layer, the thermal oxidation silicon dioxide film and part of the monocrystalline silicon substrate, and the thickness of the first and second stepped micro-cantilever array suspension structures is less than the thickness of the silicon-based fixed support body.

[0014] The working method of the multi-drive mode micro-cantilever array MEMS viscosity sensor chip according to the application comprises the following steps:

[0015] The piezoelectric electrodes arranged on the support plate and the metal layer coil arranged on the wide plate cantilever are used to excite the first and second stepped micro-cantilever array suspension structures to generate a localized vibration mode of a high-order bending mode through the coordination of piezoelectric excitation and electromagnetic excitation; when the localized vibration mode of the high-order bending mode occurs, the first stepped micro-cantilever array suspension structure has a bending vibration mode along the length and width directions, and the support plate of the first stepped micro-cantilever array suspension structure has a bending vibration mode along the length direction, and the high-order bending vibration of the second stepped micro-cantilever array suspension structure is inhibited.

[0016] The sinusoidal alternating voltage is input to the driving electrode along the same direction of the width of each piezoelectric electrode pair, the support plate is in a mode of top electrode power supply and bottom electrode grounding, all the support plates drive the respective connected wide plate cantilever to generate vibration under the action of the inverse piezoelectric effect, meanwhile, the first stepped micro-cantilever array suspension structure and the second stepped micro-cantilever array suspension structure are placed in a constant magnetic field, and the metal layer coil arranged on the wide plate cantilever is input with a sinusoidal alternating voltage when the first stepped micro-cantilever array suspension structure and the second stepped micro-cantilever array suspension structure generate bending vibration in the constant magnetic field, the wide plate cantilever generates a Lorentz force, and drives the wide plate cantilever and the first stepped micro-cantilever array suspension structure and the second stepped micro-cantilever array suspension structure to generate high-order bending vibration modes.

[0017] When the frequency of the sinusoidal alternating voltage is the same as the high-order bending mode localization natural frequency of the first stepped micro-cantilever array suspension structure and the second stepped micro-cantilever array suspension structure, high-order bending mode localization resonance vibration is generated on the support plate and the wide plate cantilever of the first stepped micro-cantilever array suspension structure, and the vibration of the support plate of the first stepped micro-cantilever array suspension structure makes another electrode on the support plate generate and output an alternating voltage detection signal due to the piezoelectric effect.

[0018] The present application has the following beneficial effects:

[0019] The multi-drive mode micro-cantilever array MEMS viscosity sensor chip of the present application adopts piezoelectric excitation and electromagnetic excitation cooperative driving mode to excite the bending vibration of the stepped micro-cantilever array suspension structure, compared with the single driving mode of the traditional viscosity sensor, the use of multi-drive mode can significantly improve the vibration driving force of the sensor chip immersed in viscous liquid, thereby improving the vibration stability and measurement accuracy; the metal layer coil arranged on the wide plate cantilever is used to generate electromagnetic excitation force for high-order bending vibration mode of the wide plate cantilever, which can provide targeted mode driving for exciting the bending vibration mode along the length and width direction of the wide plate cantilever, and ensure the vibration stability of the high-order bending vibration mode; the stepped micro-cantilever array suspension structure is used, the vibration mode localization of the stepped micro-cantilever array suspension structure is excited through the difference design of the lengths of the two wide plate cantilevers, meanwhile, the Y-shaped structure design of the connecting beam is used to further improve the transmission of the vibration energy of the stepped micro-cantilever array suspension structure to the specific stepped micro-cantilever on the basis of vibration mode localization, thereby significantly improving the vibration characteristics such as quality factor of the stepped micro-cantilever. BRIEF DESCRIPTION OF DRAWINGS

[0020] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiment description. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creating any creative labor on the basis of these drawings.

[0021] Figure 1 The overall structure schematic diagram of the multi-drive mode micro-cantilever array MEMS viscosity sensor chip of the embodiment of the present application.

[0022] Figure 2 The cross-sectional schematic diagram along A-A' in the embodiment of the present application. Figure 1

[0023] Figure 3 The localized bending vibration simulation diagram of the stepped micro-cantilever array structure in the working mode in the embodiment of the present application.

[0024] Figure 4 The bending vibration mode simulation diagram of the stepped micro-cantilever array structure in the embodiment of the present application.

[0025] In the figure, 1 is a first wide plate cantilever, 2 is a second wide plate cantilever, 3-1 is a first support plate, 3-2 is a second support plate, 4-1 is a first piezoelectric electrode pair, 4-2 is a second piezoelectric electrode pair, 5 is a stiffness connecting beam, 5-1 is a first thin beam, 5-2 is a second thin beam, 5-3 is a third thin beam, 6 is a metal layer coil, 6-1 is a convex part, 6-2 is a groove, 7 is a silicon-based fixed support body, 8 is a metal lead wire, 9 is a monocrystalline silicon substrate, 10 is a thermal oxide silicon thin film, 11 is a piezoelectric bottom electrode molybdenum thin film, 12 is a low stress aluminum nitride piezoelectric thin film, 13 is a metal layer thin film, 14 is a PECVD silicon oxide thin film (i.e. plasma enhanced chemical vapor deposition silicon oxide thin film), 15 is a first stepped micro-cantilever array suspended structure, and 16 is a second stepped micro-cantilever array suspended structure. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical scheme and advantages of the present application more clear, the embodiments of the present application will be further described in detail below with reference to the drawings.

[0027] Reference Figure 1 ​The multi-drive mode microcantilever array MEMS viscosity sensor chip of the embodiment comprises a silicon-based fixed support body 7, two stepped microcantilever array suspended structures are connected to the silicon-based fixed support body 7, the stepped microcantilever array suspended structure comprises a support plate connected to one end of the fixed support body 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 arranged on the support plate, the piezoelectric electrode pair serves as the top electrode of the support plate, and a stiffness connection beam 5 is connected between adjacent support plates; specifically, the two stepped microcantilever array suspended structures are respectively denoted as a first stepped microcantilever array suspended structure 15 and a second stepped microcantilever array suspended structure 16. The first stepped microcantilever array suspended structure 15 comprises a rectangular first support plate 3-1 and a first wide plate cantilever 1, the width of the first support plate 3-1 is smaller 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 axes of the wide edges of the first support plate 3-1 and the first wide plate cantilever 1 are coaxial; the second stepped microcantilever array suspended structure 16 comprises a rectangular second support plate 3-2 and a second wide plate cantilever 2, the width of the second support plate 3-2 is smaller 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 cantilever 2; the symmetry axes of the wide edges of the second support plate 3-2 and the second wide plate cantilever 2 are coaxial; the first support plate 3-1 and the second support plate 3-2 are of the same length, the same width and the same thickness, the symmetry axes of the wide edges of the first support plate 3-1 and the second support plate 3-2 are parallel, the first wide plate cantilever 1 and the second wide plate cantilever 2 are of the same width, the length of the second wide plate cantilever 2 is greater than that of 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 smaller than the length of the second wide plate cantilever 7; the thickness of the first wide plate cantilever 1 is the same as that of the second wide plate cantilever 2, and the width of the first wide plate cantilever 1 is the same as that of the second wide plate cantilever 2; the thickness of the stepped microcantilever array suspended structure is smaller than 5 times or more of the length and width of the support plate and smaller than 5 times or more of the length and width of the wide plate cantilever. That is, the length and width of the first support plate 3-1 are 5 times or more of the thickness, the length and width of the first wide plate cantilever 1 are 5 times or more of the thickness, the length and width of the second support plate 3-2 are 5 times or more of the thickness, and the length and width of the second wide plate cantilever 2 are 5 times or more of the thickness.The metal layer coil 6 is arranged on the surface of the first wide plate cantilever 1 and the second wide plate cantilever 2, and the metal layer coil on the first wide plate cantilever 1 and the metal layer coil on the second wide plate cantilever 2 are the same in shape and size; the metal layer coil is arranged in a rectangular concave-convex shape (similar to a comb shape), specifically, the metal layer coil has rectangular, alternately distributed convex portions 6-1 and grooves 6-2, the end of the convex portion 6-1 and the opening of the groove 6-2 are towards the free end of the first wide plate cantilever 1 or the second wide plate cantilever 2, the number of the convex portions 6-1 is even, the number of the grooves 6-2 is odd, the metal layer coil is symmetrically arranged along the symmetry axis of the first wide plate cantilever 1 or the second wide plate cantilever 2 in the length direction, and the two side edges of the metal layer coil are both set as the convex portions 6-1; the first piezoelectric electrode pair 4-1 is arranged on the first support plate 3-1, the two electrodes in the first piezoelectric electrode pair are symmetrically arranged about the symmetry axis of the first support plate 3-1 in the length direction, 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; the second piezoelectric electrode pair 4-2 is arranged on the second support plate 3-2, the two electrodes in the second piezoelectric electrode pair are symmetrically arranged about the symmetry axis of the second support plate 3-2 in the length direction, 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 the metal lead wire 8.

[0028] 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 is the same as 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, the shape of the rigidity connecting beam 5 adopts a Y shape; the rigidity connecting beam 5 is connected with the second support plate 3-2 by double thin beams and connected with 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, wherein one end of the first thin beam 5-1 is connected with the first support plate 3-1, the other end of the first thin beam 5-1 is connected with 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 connected with 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 with 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 high-order bending vibration modes are generated, the vibration frequency of the second stepped micro-cantilever plate array suspended structure 16 is lower than that of the first stepped micro-cantilever plate array suspended structure 15, that is, the vibration energy of the second stepped micro-cantilever plate array suspended structure 16 is lower than that of the first stepped micro-cantilever plate array suspended structure 15, and at the same time, through the design of the Y-shaped rigidity connecting beam 5, the transmission effect of the vibration energy from the second stepped micro-cantilever plate array suspended structure 16 to the first stepped micro-cantilever plate array suspended structure 15 can be enhanced, thereby improving the vibration characteristics of the first stepped micro-cantilever plate array suspended structure 15.

[0029] The length direction is along the direction of X in the figure, and the width direction is along the direction of Y in the figure. 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.

[0030] The working method of the multi-drive mode micro-cantilever plate array MEMS viscosity sensor chip according to the embodiment of the present application is as follows:

[0031] 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, and 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, adopt a piezoelectric excitation and electromagnetic excitation synergistic mode to excite the first stepped micro-cantilever array suspended structure 15 and the second stepped micro-cantilever 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 stepped micro-cantilever array suspended structure 15 has a significant bending vibration mode 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 stepped micro-cantilever array suspended structure 16 is suppressed.

[0032] The driving electrodes along the same direction of the width of each piezoelectric electrode pair are connected with sinusoidal alternating voltage, and the support plate forms a top electrode connected with power and a bottom electrode connected with ground, that is, the driving electrodes along the same direction of the width of the first piezoelectric electrode pair 4-1 are connected with sinusoidal alternating voltage, and the first support plate 3-1 forms a top electrode connected with power and a bottom electrode connected with ground, and the driving electrodes along the same direction of the width of the second piezoelectric electrode pair 4-2 are connected with sinusoidal alternating voltage, and the second support plate 3-2 forms a top electrode connected with power and a bottom electrode connected with ground; all support plates drive the respective connected wide plate cantilever 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, 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 produces bending vibration in the constant magnetic field, and the metal layer coil 6 arranged in the wide plate cantilever (including the first wide plate cantilever 1 and the second wide plate cantilever 2) is connected with sinusoidal alternating voltage to produce Lorentz force on the wide plate cantilever (including the first wide plate cantilever 1 and the second wide plate cantilever 2), drive the wide plate cantilever (including the first wide plate cantilever 1 and the second wide plate cantilever 2) and the whole 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 produce high-order bending vibration mode. That is, the first stepped micro-cantilever plate suspended structure 15 is placed in a constant magnetic field and produces bending vibration in the constant magnetic field, and the metal layer coil 6 arranged in the first wide plate cantilever 1 is connected with sinusoidal alternating voltage to produce Lorentz force on the first wide plate cantilever 1, drive the first wide plate cantilever 1 and the whole first stepped micro-cantilever plate suspended structure 15 to produce high-order bending vibration mode; the second stepped micro-cantilever plate suspended structure 16 is placed in a constant magnetic field and produces bending vibration in the constant magnetic field, and the metal layer coil 6 arranged in the second wide plate cantilever 2 is connected with sinusoidal alternating voltage to produce Lorentz force on the second wide plate cantilever 2, drive the second wide plate cantilever 2 and the whole second stepped micro-cantilever plate suspended structure 16 to produce high-order bending vibration mode.

[0033] 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), the first support plate 3-1 and the first wide plate cantilever 1 of the first stepped micro-cantilever plate array suspended structure 15 produce localized resonant vibration of high-order bending mode, 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.

[0034] The sensor chip of the present application adopts a stepped micro-cantilever array structure to excite the mode localization of high-order bending vibration, thereby measuring the viscosity of fluid. The micro-cantilever array under the mode generates energy localization phenomenon, so that the overall vibration energy is transmitted to a single stepped micro-cantilever structure, and a high-order bending vibration mode is used as a working mode, thereby improving the vibration damping resistance of a specific micro-cantilever immersed in viscous fluid.

[0035] In the embodiment, the size of the first wide plate cantilever 1 is: length x width = (550±5) x (1000±5) μm 2 , and the thickness is 20±5 μm; the size of the second wide plate cantilever 2 is: length x width = (700±5) x (1000±5) μm 2 , and the thickness is 20±5 μm; the size of the first support plate 3-1 and the second support plate 3-2 is: length x width = (300±10) x (280±10) μm 2 , and the thickness is 20±5 μm; the thickness of the stiffness connection beam 5 is 20±5 μm, the length of the first thin beam 5-1 is 500±5 μm, the length of the second thin beam 5-2 is 300±5 μm, the included 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±3 μm.

[0036] As shown in Figure 2 , the cross-sectional view of the MEMS viscosity sensor chip of the stepped micro-cantilever array structure in the embodiment, the sensor chip is prepared by a single crystal silicon substrate 9, both upper and lower surfaces (i.e. top surface and back surface) of the single crystal silicon substrate 9 are covered with a thermal oxide silicon dioxide film 10, the thermal oxide silicon dioxide film 10 is used as an insulation layer of the single crystal silicon substrate 9, and the thermal oxide silicon dioxide film 10 on the bottom surface (i.e. back surface) of the single crystal silicon substrate 9 is finally removed; the surface of the thermal oxide 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, the surface of the piezoelectric layer bottom electrode molybdenum film 11 is provided with an aluminum nitride piezoelectric film 12, the piezoelectric layer bottom electrode molybdenum film 11 can be used as a chip bottom electrode ground or as a substrate layer for deposition of the aluminum nitride piezoelectric film 12; the piezoelectric film of the sensor chip adopts an aluminum nitride film, which is used to generate inverse piezoelectric effect and piezoelectric effect, to realize excitation of vibration mode and detection of electric signal; the surface of the aluminum nitride piezoelectric film 12 is provided with a metal film 13, which 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; the top surface of the aluminum nitride piezoelectric film 12 and the metal film 13 is provided with a PECVD silicon oxide film 14, which covers the entire top surface of the sensor chip and is used for insulation in a fluid medium. Figure 2The region with a larger thickness of the left single crystal silicon substrate 9 represents a silicon base fixed body 7 of the sensor chip, and the region with a smaller thickness of the single crystal silicon substrate 9 represents a stepped micro-cantilever plate suspended structure, specifically, a first stepped micro-cantilever plate array suspended structure 15 and a 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 molybdenum film 11, the thermal oxygen 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, part of the top of the single crystal silicon substrate 9).

[0037] As Figure 3 With Figure 4 , Comsol Multiphysics multi-physical field simulation software is used to perform fluid-solid coupling simulation analysis on the stepped micro-cantilever plate suspended array structure of the embodiment, and n-heptane (density of 684 kg / m 3 , viscosity of 0.4 cP) is selected as the simulated viscous liquid, and the piezoelectric excitation force is 5 μN. Figure 3 is the simulation result of the first micro-cantilever plate in the localized high-order bending vibration mode, Figure 4 is the simulation result of the relationship between the vibration amplitude and the fluid viscosity of the first micro-cantilever plate in the localized high-order bending vibration mode, wherein Figure 3 is the working mode adopted by the viscosity sensor chip of the present application. Figure 3 The resonant frequency of the stepped micro-cantilever plate suspended array structure obtained in the embodiment is 149270 Hz, Figure 4 In the embodiment, n-heptane, cyclohexane, MD2M and D4 liquids with different viscosity values are simulated and analyzed to obtain the relationship curve between the vibration of the stepped micro-cantilever plate suspended structure and the fluid viscosity, and then the corresponding relationship between the vibration amplitude and the fluid viscosity 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 application.

[0038] In summary, the stepped micro-cantilever plate suspended structure in the present application is covered with a low-stress aluminum nitride piezoelectric film and a metal layer coil, and a piezoelectric excitation and electromagnetic excitation are used in a coordinated manner to excite the micro-cantilever plate array structure to produce a localized high-order bending vibration mode, and the Y-shaped stiffness link beam design improves the localization of the vibration mode of the overall stepped micro-cantilever plate suspended structure, thereby improving the vibration characteristics of the sensor chip in the viscous fluid. The resonant stress generated by the stepped micro-cantilever plate suspended structure can be converted into an electrical signal output through the piezoelectric effect, and the viscosity sensor chip can improve the measurement accuracy of the fluid viscosity and has piezoelectric self-detection performance in the fluid.

[0039] From the above scheme, the MEMS viscosity sensor chip based on the ladder micro-cantilever plate structure has the advantages of simple structure, flexible modal driving mode, mature preparation process, etc., and adopts high-order bending vibration mode, which is used to increase the vibration stiffness, enhance the fluid damping resistance of the sensor chip immersed in the viscous fluid, and thus improve the fluid viscosity measurement accuracy, stability and other measurement performances of the sensor.

[0040] Finally, it should be noted that: the above examples are only used to illustrate the technical solutions of the present application, but not to limit it, although the present application has been described in detail with reference to the above examples, those skilled in the art should understand that: the specific embodiments of the present application can still be modified or replaced by the equivalent, without departing from the spirit and scope of the present application, any modification or equivalent replacement, which should be covered within the protection scope of the claims of the present application.

Claims

1. A multi-actuation mode microcantilever array MEMS viscosity sensor chip, characterized in that, The application relates to a piezoelectric sensor, which comprises a silicon base fixed body (7), a first ladder-shaped micro-cantilever plate array suspension structure (15) and a second ladder-shaped micro-cantilever plate array suspension structure (16) connected to the silicon base fixed body (7), the first ladder-shaped micro-cantilever plate array suspension structure (15) and the second ladder-shaped micro-cantilever plate array suspension structure (16) each comprise a support plate and a wide plate cantilever arranged coaxially in a rectangular shape, the two ends of the support plate are connected with the silicon base fixed body and the wide plate cantilever respectively, and the width of the support plate is smaller than that of the wide plate cantilever; a metal layer coil (6) is arranged on the surface of the wide plate cantilever; a piezoelectric electrode pair is arranged on the support plate, the two electrodes of the piezoelectric electrode pair are symmetrically arranged about the symmetry axis of the support plate in the length direction, and each electrode is connected with a metal lead wire (8); a stiffness connecting beam (5) is connected between the support plates of the first ladder-shaped micro-cantilever plate array suspension structure (15) and the second ladder-shaped micro-cantilever plate array suspension structure (16), the sizes of the support plates of the first ladder-shaped micro-cantilever plate array suspension structure (15) and the second ladder-shaped micro-cantilever plate array suspension structure (16) are the same, the length of the wide plate cantilever of the first ladder-shaped micro-cantilever plate array suspension structure (15) is smaller than that of the wide plate cantilever of the second ladder-shaped micro-cantilever plate array suspension structure (16), and the width of the wide plate cantilever of the first ladder-shaped micro-cantilever plate array suspension structure (15) is equal to that of the wide plate cantilever of the second ladder-shaped micro-cantilever plate array suspension structure (16).

2. The multi-actuation mode microcantilever array MEMS viscosity sensor chip according to claim 1, wherein, The metal layer coil (6) is in a comb shape, and the tooth part of the metal layer coil (6) faces the free end of the wide plate cantilever.

3. The multi-actuation mode microcantilever array MEMS viscosity sensor chip according to claim 2, wherein, The tooth part of the metal layer coil (6) comprises rectangular and alternately distributed convex parts (6-1) and grooves (6-2), the end part of the convex part (6-1) and the opening of the groove (6-2) face the free end of the wide plate cantilever, the number of the convex parts (6-1) is even, the number of the grooves (6-2) is odd, the metal layer coil (6) is symmetrically arranged along the length direction of the wide plate cantilever, and the two side edges of the metal layer coil (6) are provided as the convex parts (6-1).

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

5. The multi-actuation mode microcantilever array MEMS viscosity sensor chip according to claim 1, wherein, The stiffness connecting beam (5) is in a Y shape, comprising 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 with the support plate of the first ladder-shaped micro-cantilever plate array suspension structure (15), the other end of the first thin beam (5-1) is connected with 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 connected with the support plate of the second ladder-shaped micro-cantilever plate array suspension structure (16).

6. The multi-actuation mode microcantilever array MEMS viscosity sensor chip of claim 1, wherein, The electrodes of the piezoelectric electrode pair are in a rectangular shape, and the length, width and thickness of all the electrodes are the same; the length of the electrode is the same as the length of the support plate.

7. The multi-actuation mode microcantilever array MEMS viscosity sensor chip according to claim 1, wherein, In the first ladder micro-cantilever plate array suspension structure (15) and the second ladder micro-cantilever plate array suspension structure (16), the width of the support plate is 26%-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) is the same.

8. The multi-actuation mode microcantilever array MEMS viscosity sensor chip of claim 1, wherein, The silicon-based fixed body (7) comprises a monocrystalline silicon substrate (9), the top surface of the monocrystalline silicon substrate (9) is covered with a thermal oxygen silicon dioxide film (10), the surface of the thermal oxygen silicon dioxide film (10) is provided with a molybdenum film (11) of a bottom electrode of a piezoelectric layer, the surface of the molybdenum film (11) of the bottom electrode of the piezoelectric layer is provided with a low-stress aluminum nitride piezoelectric film (12), the surface of the low-stress aluminum nitride piezoelectric film (12) is provided with a metal film (13) used for forming a pair of piezoelectric electrodes, a metal layer coil (6) and a metal lead wire (8), and the top surfaces of the low-stress aluminum nitride piezoelectric film (12) and the metal film (13) are covered with a PECVD silicon oxide film (14); the first ladder micro-cantilever plate array suspension structure (15) and the second ladder micro-cantilever plate array suspension structure (16) share the PECVD silicon oxide film (14), the metal film (13), the low-stress aluminum nitride piezoelectric film (12), the molybdenum film (11) of the bottom electrode of the piezoelectric layer, the thermal oxygen silicon dioxide film (10) and part of the monocrystalline silicon substrate (9) of the silicon-based fixed body (7), wherein the thickness of the monocrystalline silicon substrate (9) on the first ladder micro-cantilever plate array suspension structure (15) and the second ladder micro-cantilever plate array suspension structure (16) is less than the thickness of the monocrystalline silicon substrate (9) on the silicon-based fixed body (7).

9. The method of operating a multi-actuated mode microcantilever array MEMS viscosity sensor chip according to any one of claims 1-8, wherein, Comprise: By the piezoelectric electrode pair arranged on the support plate and the metal layer coil (6) arranged on the wide plate cantilever, the piezoelectric excitation and the electromagnetic excitation are coordinated to excite the first ladder micro-cantilever plate array suspension structure (15) and the second ladder micro-cantilever plate array suspension 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 ladder micro-cantilever plate array suspension structure (15) has a bending vibration mode along the length and width directions, and the support plate of the first ladder micro-cantilever plate array suspension structure (15) has a bending vibration mode along the length direction, at this time, the high-order bending vibration of the second ladder micro-cantilever plate array suspension structure (16) is inhibited; A sinusoidal alternating voltage is applied to the driving electrode in the same direction along the width of the support plate in each piezoelectric electrode pair, the support plate is in a top electrode power supply and bottom electrode grounding mode, and all the support plates drive the respective connected wide plate cantilevers to vibrate under the action of the inverse piezoelectric effect, at the same time, the first ladder micro-cantilever plate array suspension structure (15) and the second ladder micro-cantilever plate array suspension structure (16) are placed in a constant magnetic field, and when the wide plate cantilever arranged metal layer coil (6) is applied with a sinusoidal alternating voltage, the wide plate cantilever generates a Lorentz force, which drives the wide plate cantilever and the first ladder micro-cantilever plate array suspension structure (15) and the second ladder micro-cantilever plate array suspension structure (16) to generate a high-order bending vibration mode; When the sine alternating voltage frequency is the same as the high order bending mode localized natural frequency of the first stepped micro-cantilever array suspended structure (15) and the second stepped micro-cantilever array suspended structure (16), high order bending mode localized resonant vibration is generated on the support plate and the wide plate cantilever of the first stepped micro-cantilever array suspended structure (15), and the vibration of the support plate of the first stepped micro-cantilever array suspended structure (15) makes another electrode on the support plate generate and output an alternating voltage detection signal due to the piezoelectric effect.

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