Vibration coupling double-micro-cantilever slab MEMS viscosity sensor chip and working method thereof

Abstract

The invention belongs to the field of MEMS sensors, and particularly relates to a vibration coupling double-micro-cantilever plate MEMS viscosity sensor chip and a working method thereof.The chip comprises a silicon-based clamped support body, a clamped support body cavity is formed in the silicon-based clamped support body, a first micro-cantilever plate and a second micro-cantilever plate are arranged in the clamped support body cavity, and the free ends of the first micro-cantilever plate and the second micro-cantilever plate are oppositely arranged; a vibration coupling gap is formed between the free ends of the first micro-cantilever plate and the second micro-cantilever plate, and the length of the second micro-cantilever plate is smaller than that of the first micro-cantilever plate; a first piezoelectric driving electrode and a first piezoelectric vibration pickup electrode are symmetrically arranged on the first micro-cantilever plate in the width direction of the first micro-cantilever plate, and a second piezoelectric driving electrode and a second piezoelectric vibration pickup electrode are symmetrically arranged on the second micro-cantilever plate in the width direction of the second micro-cantilever plate. The first piezoelectric driving electrode, the first piezoelectric vibration pick-up electrode, the second piezoelectric driving electrode and the second piezoelectric vibration pick-up electrode are all connected with metal leads. The vibration coupling double-micro-cantilever slab MEMS viscosity sensor chip can remarkably improve the measurement performance such as fluid measurement precision and stability.

Description

Technical Field

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

[0002] In the chemical industry, fluid viscosity is used as an important indicator of quality control. The existing traditional viscometers such as rotating cylinders have the disadvantages of bulky equipment, high measurement cost, and low efficiency, which can hardly meet the application requirements of efficient fluid detection. Faced with the above viscosity measurement problems, viscosity sensors based on MEMS technology have the advantages of low manufacturing cost, miniaturized integration, and online measurement. In recent years, they have shown good research and development potential and application prospects. However, most of the current MEMS viscosity sensors rely on the resonant measurement method with quality factor as the key vibration parameter. For the measurement of high-viscosity fluids in many industries such as energy and chemical industry, the performance improvement of such sensors is restricted by problems such as poor fluid measurement accuracy, low quality factor, and cumbersome sensor measurement process. Therefore, it is necessary to take MEMS viscosity sensors as the research object, and optimize the design of sensors from the aspects of sensor structure design and its working mechanism, so as to improve the comprehensive measurement performance of such sensors, such as measurement accuracy and viscosity application range. 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 vibration-coupled dual micro-cantilever plate MEMS viscosity sensor chip and a working method thereof, in order to improve the comprehensive performance of the MEMS viscosity sensor, such as measurement accuracy, measurement range, and stability.

[0004] In order to achieve the above object, the present invention adopts the following technical solution: A vibration-coupled dual micro-cantilever plate MEMS viscosity sensor chip, comprising a silicon-based solid support, a solid support cavity is provided on the silicon-based solid support, a dual piezoelectric micro-cantilever plate suspension structure is provided in the solid support cavity on the silicon-based solid support, the dual piezoelectric micro-cantilever plate suspension structure comprises a first micro-cantilever plate and a second micro-cantilever plate which are rectangular and have free ends arranged opposite to each other, a vibration coupling gap is provided between the free end of the first micro-cantilever plate and the free end of the second micro-cantilever plate, and the length of the second micro-cantilever plate is less than the length of the first micro-cantilever plate; The first micro-cantilever plate is symmetrically provided with a first piezoelectric driving electrode and a first piezoelectric pickup electrode in its width direction, and the second micro-cantilever plate is symmetrically provided with a second piezoelectric driving electrode and a second piezoelectric pickup electrode in its width direction. The first piezoelectric driving electrode and the second piezoelectric driving electrode are located on the same side, and the first piezoelectric pickup electrode and the second piezoelectric pickup electrode are located on the same side. The first piezoelectric driving electrode, the first piezoelectric pickup electrode, the second piezoelectric driving electrode and the second piezoelectric pickup electrode are all connected with metal leads.

[0005] Preferably, the first micro-cantilever plate and the second micro-cantilever plate have the same width and thickness, the width of the first micro-cantilever plate is greater than or equal to the length, and the width and length of the first micro-cantilever plate are both more than 5 times the thickness; the width of the second micro-cantilever plate is greater than or equal to the length, and the width and length of the second micro-cantilever plate are both more than 5 times the thickness.

[0006] Preferably, a first rectangular protrusion is provided at the free end of the first micro-cantilever plate, and the first piezoelectric driving electrode and the first piezoelectric pickup electrode are symmetrically located on both sides of the first rectangular protrusion; a second rectangular protrusion is provided at the free end of the second micro-cantilever plate, and the second piezoelectric driving electrode and the second piezoelectric pickup electrode are symmetrically located on both sides of the second rectangular protrusion, the first rectangular protrusion and the second rectangular protrusion are directly opposite to each other, and a gap is left between the first rectangular protrusion and the second rectangular protrusion.

[0007] Preferably, the first micro cantilever plate has the same thickness as the first rectangular protrusion, the second micro cantilever plate has the same thickness as the second rectangular protrusion, and the first rectangular protrusion and the second rectangular protrusion have the same length, width and thickness.

[0008] Preferably, the net distance between the first rectangular protrusion and the second rectangular protrusion is 33% to 48% of the width of the vibration coupling gap, the width of the first rectangular protrusion is 33% to 36% of the width of the first micro-cantilever plate, the width of the second rectangular protrusion is 33% to 36% of the width of the second micro-cantilever plate, and the length of the second micro-cantilever plate is 80% to 84% of the length of the first micro-cantilever plate.

[0009] Preferably, the first piezoelectric driving electrode and the first piezoelectric pickup electrode have the same length, width and thickness; the second piezoelectric driving electrode and the second piezoelectric pickup electrode have the same length, width and thickness.

[0010] Preferably, the first piezoelectric driving electrode, the first piezoelectric pickup electrode and the first micro-cantilever plate have the same length, and the second piezoelectric driving electrode, the second piezoelectric pickup electrode and the second micro-cantilever plate have the same length.

[0011] Preferably, the shape of the cavity of the support body is rectangular, and the symmetry axis of the first micro-cantilever plate and the second micro-cantilever plate in the length direction is coaxial with the symmetry axis of the wide side of the cavity of the support body.

[0012] Preferably, the silicon-based solid support body comprises a single crystal silicon substrate, the bottom and top surfaces of the single crystal silicon substrate are both provided with a thermal oxidized silicon film, the surface of the thermal oxidized silicon film on the top surface of the single crystal silicon substrate is provided with a piezoelectric layer bottom electrode molybdenum film, the surface of the piezoelectric layer bottom electrode molybdenum film is provided with a low stress aluminum nitride piezoelectric film, the surface of the low stress aluminum nitride piezoelectric film is provided with an electrode metal layer used as a first piezoelectric driving electrode, a first piezoelectric pickup electrode, a second piezoelectric driving electrode and a second piezoelectric pickup electrode, and the surfaces of the low stress aluminum nitride piezoelectric film and the electrode metal layer are provided with a silicon nitride film; the first micro-cantilever plate, the second micro-cantilever plate and the silicon-based solid support body share the thermal oxidized silicon film, the piezoelectric layer bottom electrode molybdenum film, the low stress aluminum nitride piezoelectric film, the silicon nitride film and part of the single crystal silicon substrate on the top surface of the single crystal silicon substrate, wherein the thickness of the single crystal silicon substrate on the first micro-cantilever plate and the second micro-cantilever plate is less than the single crystal silicon substrate of the silicon-based solid support body.

[0013] The present invention also provides a working method of the vibration-coupled dual micro-cantilever plate MEMS viscosity sensor chip as described above, comprising: When the vibration-coupled dual micro-cantilever plate MEMS viscosity sensor chip is immersed in a fluid, the fluid fills the vibration coupling gap and acts as a vibration coupling medium; The first micro-cantilever plate is used as an active cantilever plate. When an alternating electric field is applied to the first piezoelectric driving electrode of the first micro-cantilever plate, the top electrode of the piezoelectric layer of the first micro-cantilever plate is energized and the bottom electrode is grounded, so that the first micro-cantilever plate generates non-resonant bending vibration at the frequency of the driving voltage, and at the same time drives the fluid around the first micro-cantilever plate to generate corresponding vibration; the second micro-cantilever plate is used as a passive cantilever plate, and generates vibration coupling with the first cantilever plate through the fluid medium, and the fluid medium in the vibration coupling gap is subjected to shear force between the first micro-cantilever plate and the second micro-cantilever plate, so that the vibration amplitude of the second micro-cantilever plate is directly related to the fluid viscosity and the vibration amplitude of the first micro-cantilever plate; when the first micro-cantilever plate and the second micro-cantilever plate are in a non-resonant bending vibration state, the first piezoelectric pickup electrode and the second piezoelectric pickup electrode constitute a top electrode externally connected to an electrical output port and the bottom electrode is grounded, and an alternating voltage detection signal is generated and output through the piezoelectric effect, and then the output voltage ratio of the dual piezoelectric micro-cantilever plate suspended structure is extracted to achieve the measurement of fluid viscosity.

[0014] The present invention has the following beneficial effects: The vibration-coupled dual micro-cantilever plate MEMS viscosity sensor chip of the present invention adopts a dual piezoelectric micro-cantilever plate structure. Compared with the traditional slender micro-cantilever beam structure, it can have a high Reynolds number by increasing the width size, which helps to improve the fluid damping resistance of the sensor chip immersed in the fluid, thereby improving the vibration stability of the sensor. The present invention uses a fluid medium to realize the vibration coupling between the dual piezoelectric micro-cantilever plate structures, and drives the passive piezoelectric micro-cantilever plate (i.e., the second micro-cantilever plate) to generate a non-resonant bending vibration of a specific frequency through the non-resonant vibration of the active piezoelectric micro-cantilever plate (i.e., the first micro-cantilever plate) and the fluid medium vibration coupling. Compared with the existing resonant fluid viscosity measurement method based on the quality factor vibration parameter, the viscosity sensor chip working method proposed by the present invention does not require resonance curve fitting, and at the same time avoids the problem that the sensor has poor fluid viscosity measurement accuracy due to the complexity of the quality factor in high-viscosity fluids, and even the problem that it is difficult to measure the fluid viscosity experimental value. The direct measurement of the fluid viscosity is realized by the sensor output vibration amplitude, which can significantly improve the measurement efficiency and accuracy. The vibration-coupled dual piezoelectric micro-cantilever plate MEMS viscosity sensor chip of the present invention realizes piezoelectric driven vibration and output voltage detection of the dual piezoelectric micro-cantilever plate suspended structure through the arrangement of piezoelectric driving electrodes and vibration pickup electrodes. Compared with electromagnetic, electrothermal and electrostatic excitation methods, it has excellent packaging characteristics and anti-interference capabilities. 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 1 Schematic diagram of the overall structure of the vibration-coupled dual micro-cantilever plate MEMS viscosity sensor chip in 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 bending vibration mode of the micro-cantilever plate suspended array structure according to an embodiment of the present invention.

[0019] Figure 4 It is a simulation curve diagram of the vibration amplitude ratio of the micro-cantilever plate suspended array structure in different fluids according to an embodiment of the present invention.

[0020] In the figure, 1-silicon-based solid support, 2-first micro-cantilever plate, 3-1-first piezoelectric driving electrode, 3-2-first piezoelectric pickup electrode, 4-second micro-cantilever plate, 5-1-second driving electrode, 5-2-second pickup electrode, 6-metal lead, 7-solid support cavity, 8-single crystal silicon substrate, 9-thermal oxygen oxide silicon film, 10-piezoelectric layer bottom electrode molybdenum film, 11-low stress aluminum nitride piezoelectric film, 12-electrode metal layer, 13-silicon nitride film, 14-rectangular protrusion, 15-vibration coupling gap. 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 vibration-coupled dual micro-cantilever plate MEMS viscosity sensor chip of this embodiment comprises a silicon-based solid support body 1, a rectangular solid support body cavity 7 is provided on the silicon-based solid support body 1, a dual piezoelectric micro-cantilever plate suspension structure is provided in the solid support body cavity 7 on the silicon-based solid support body 1, and the dual piezoelectric micro-cantilever plate suspension structure comprises a rectangular first micro-cantilever plate 2 and a second micro-cantilever plate 4 with free ends arranged opposite to each other, the symmetry axis of the first micro-cantilever plate 2 and the second micro-cantilever plate 4 in the length direction is coaxial with the symmetry axis of the wide side of the solid support body cavity 7, and a vibration coupling gap 15 is provided between the free end of the first micro-cantilever plate 2 and the free end of the second micro-cantilever plate 4; the length of the second micro-cantilever plate 4 is less than the length of the first micro-cantilever plate 2; the first micro-cantilever plate 2 and the second micro-cantilever plate 4 have the same width and thickness; The width and length of the first micro-cantilever plate 2 are both more than 5 times the thickness; the width of the second micro-cantilever plate 4 is greater than or equal to the length, and the width and length of the second micro-cantilever plate 4 are both more than 5 times the thickness; a rectangular protrusion 14 is provided at the end of the free end of the first micro-cantilever plate 2 and the second micro-cantilever plate 4, the rectangular protrusion 14 in the first micro-cantilever plate 2 and the second micro-cantilever plate 3 are the same size, the rectangular protrusion 14 on the first micro-cantilever plate 2 and the rectangular protrusion 14 on the second micro-cantilever plate 4 are directly opposite, and a gap is left between the two rectangular protrusions; the first micro-cantilever plate 2 has the same thickness as the rectangular protrusion thereon, the second micro-cantilever plate 4 has the same thickness as the rectangular protrusion thereon, and the two rectangular protrusions 14 have the same length, width and thickness; the silicon-based fixed support plate 1 and The lower bottoms of the first micro-cantilever plate 2 and the second micro-cantilever plate 4 are coaxially connected; the first micro-cantilever plate 2 and the second micro-cantilever plate 4 are coaxially arranged along the length direction, and there is a free end gap width between the two; the dual piezoelectric micro-cantilever plate suspended structure is arranged with a piezoelectric electrode pair, wherein the first micro-cantilever plate 2 is arranged with a first piezoelectric driving electrode 3-1 and a first piezoelectric pickup electrode 3-2, and the second micro-cantilever plate 4 is arranged with a piezoelectric pickup electrode pair (i.e., a second piezoelectric driving electrode 5-1 and a second piezoelectric pickup electrode 5-2), and the piezoelectric electrode pairs are both used as top electrodes of the dual piezoelectric micro-cantilever plate suspended structure; the piezoelectric electrode pairs on the dual piezoelectric micro-cantilever plate suspended structure are symmetrical about the symmetry axis in the width direction of the rectangular protrusion 14, and are arranged on both sides of the micro-cantilever plate along the width direction, that is, the first micro The first piezoelectric driving electrode 3-1 and the first piezoelectric pickup electrode 3-2 on the cantilever plate 2 are symmetrical about the symmetry axis in the width direction of the rectangular protrusion 14, and the second piezoelectric driving electrode 5-1 and the second piezoelectric pickup electrode 5-2 on the second micro-cantilever plate 4 are symmetrical about the symmetry axis in the width direction of the rectangular protrusion 14. The first piezoelectric driving electrode 3-1 and the second piezoelectric driving electrode 5-1 are located on the same side, and the first piezoelectric pickup electrode 3-2 and the second piezoelectric pickup electrode 5-2 are located on the same side; the piezoelectric driving electrode and the pickup electrode on the same micro-cantilever plate (i.e., the first micro-cantilever plate 2 or the second micro-cantilever plate 4) have the same length, width, and thickness, and the length of the piezoelectric driving electrode and the pickup electrode is the same as the length of the micro-cantilever plate (i.e., the first micro-cantilever plate 2 or the second micro-cantilever plate 4);The width dimension of the dual piezoelectric micro cantilever plate suspended structure is greater than or equal to the length dimension; each piezoelectric driving electrode and piezoelectric pickup electrode is connected to a metal lead 6. The length direction is along; Figure 1 The X direction is parallel to the axial direction of the length direction of the micro cantilever plate, and the Y direction is the width direction, which is along the width direction of the micro cantilever plate.

[0023] Reference Figure 1 Combined with Figure 3 The working method of the vibration-coupled dual micro-cantilever plate MEMS viscosity sensor chip of this embodiment includes the following steps: When the vibration-coupled dual micro-cantilever plate MEMS viscosity sensor chip is immersed in a fluid, the fluid will fill the free end gap between the dual piezoelectric micro-cantilever plate suspended structures (i.e., the gap between the free ends of the first micro-cantilever plate 2 and the second micro-cantilever plate 4) and act as a vibration coupling medium. The first micro-cantilever plate 2 acts as an active cantilever plate. When an alternating electric field is applied to the first piezoelectric driving electrode 3-1 of the first micro-cantilever plate 2, the top electrode of the piezoelectric layer of the first micro-cantilever plate 2 is energized and the bottom electrode is grounded, so that the first micro-cantilever plate 2 generates non-resonant bending vibration at the frequency of the driving voltage, and at the same time drives the surrounding fluid to generate corresponding vibration. Further, the surrounding fluid vibration generates a vibration driving force on the second micro-cantilever plate 4, so that the second micro-cantilever plate 4 generates passive bending vibration at a specific frequency. The second micro-cantilever plate 4 acts as a passive cantilever plate, and generates vibration coupling with the first cantilever plate 2 through the fluid medium, and the fluid medium in the gap at the free end of the suspended structure of the dual piezoelectric micro-cantilever plate is subjected to shear force between the first and second micro-cantilever plates (2, 4), so that the vibration amplitude of the second micro-cantilever plate 4 is directly related to the fluid viscosity and the vibration amplitude of the first micro-cantilever plate 2. When the first and second micro-cantilever plates are in a non-resonant bending vibration state, the piezoelectric pickup electrode also forms a mode in which the top electrode is externally connected to the electrical output port and the bottom electrode is grounded, and an alternating voltage detection signal is generated and output through the piezoelectric effect, thereby extracting the output voltage ratio of the suspended structure of the dual piezoelectric micro-cantilever plate to achieve the measurement of fluid viscosity.

[0024] The vibration-coupled dual micro-cantilever plate MEMS viscosity sensor chip of the present invention adopts a dual piezoelectric micro-cantilever plate suspended structure with a free end gap (i.e., a vibration coupling gap 15) to stimulate the vibration coupling effect of the dual micro-cantilever plate through a fluid medium; through the structural design of the rectangular protrusion 14 on the micro-cantilever plate, the fluid medium in the free end gap (i.e., the vibration coupling gap 15, which can be determined by experiments and can be designed according to the type of the detected fluid and the overall size of the sensor, and the present invention does not make specific restrictions, as long as vibration coupling can occur between the first micro-cantilever plate 2 and the second micro-cantilever plate 4) produces uneven vibration distribution, thereby improving the bending vibration transmission effect of the fluid on the dual micro-cantilever plate; a dual cantilever plate structure in a non-resonant bending vibration state is adopted, and the fluid viscosity is measured by the sensor vibration amplitude, so as to avoid the problem of poor fluid viscosity measurement accuracy caused by the difficulty in accurately fitting complex resonant parameters such as quality factor in high-viscosity fluids, thereby improving the working performance of this type of sensor, such as fluid viscosity measurement accuracy and measurement efficiency.

[0025] The size of the first micro cantilever plate 2 of the dual piezoelectric micro cantilever plate suspended structure in this embodiment is: length × width = (1100 ± 10) × (1400 ± 10) μm 2 , thickness is 20±5μm; the size of the second micro cantilever plate 4 is: length × width = (900±10) × (1400±10) μm 2 , thickness is 20±5μm; the size of the rectangular protrusion 14 is: length × width = (30±5) × (480±10) μm 2 , the thickness is 20±5μm; the length of the vibration coupling gap 15 at the free end of the first micro-cantilever plate 2 and the second micro-cantilever plate 4 is 100±5μm, that is, the distance between the two rectangular protrusions 14 of the first micro-cantilever plate 2 and the second micro-cantilever plate 4 is 40±5μm.

[0026] like Figure 2As shown in the cross-sectional view of the vibration-coupled micro-cantilever plate MEMS viscosity sensor chip of the present invention, the sensor chip is prepared from a single crystal silicon substrate 8, and the upper and lower surfaces of the single crystal silicon substrate 8 are covered with a thermal oxide silicon film 9, and the thermal oxide silicon film 9 is used as an electrical insulation layer of the single crystal silicon substrate; a piezoelectric layer bottom electrode molybdenum film 10 is provided on the surface of the thermal oxide silicon film 9 on the upper side of the single crystal silicon substrate 8, and the piezoelectric layer bottom electrode molybdenum film 10 can be used as a chip bottom electrode grounding, and can also be used as a substrate layer for the deposition of a low stress aluminum nitride piezoelectric film 11; the upper surface of the piezoelectric layer bottom electrode molybdenum film 10 A low-stress aluminum nitride piezoelectric film 11 is provided, which is used to generate the inverse piezoelectric effect and the piezoelectric effect, and realize the excitation of the vibration mode and the detection of the electrical signal; an electrode metal layer 12 is provided on the upper surface of the low-stress aluminum nitride piezoelectric film 11, and the electrode metal layer 12 is used to form a piezoelectric electrode pair and a metal lead 6; a silicon nitride insulating layer film 13 is provided on the upper side of the low-stress aluminum nitride piezoelectric film 11 and the electrode metal layer 12, and the silicon nitride insulating layer film 13 covers the surface of the sensor chip, and the silicon nitride insulating layer film 13 is used for insulation in the fluid medium. Figure 2 The area with a larger thickness of the single crystal silicon substrate 8 on the left side of the cross-sectional view represents the silicon-based fixed support body 1 of the sensor chip, and the area with a smaller thickness of the single crystal silicon substrate 8 represents the suspended structure of the dual piezoelectric micro-cantilever plate. Specifically, the first micro-cantilever plate 2, the second micro-cantilever plate 4 and the silicon-based fixed support body 1 share the thermally oxidized silicon film 9 on the top surface of the single crystal silicon substrate 8, the piezoelectric layer bottom electrode molybdenum film 10, the low stress aluminum nitride piezoelectric film 11, the silicon nitride film 14 and part of the single crystal silicon substrate 8, wherein the thickness of the single crystal silicon substrate 8 on the first micro-cantilever plate 2 and the second micro-cantilever plate 4 is less than the single crystal silicon substrate 8 of the silicon-based fixed support body 1.

[0027] like Figure 3 and Figure 4 As shown, Comsol Multiphysics multi-physics field simulation software is used to perform fluid-solid coupling simulation analysis on the dual piezoelectric micro-cantilever plate suspended structure of the above embodiment size. Figure 3 The simulation results of the non-resonant bending vibration of the first micro-cantilever plate 2 and the second micro-cantilever plate 4 under the vibration coupling effect are shown in Figure 2. The simulation liquid is cyclohexane (density 779 kg / m 3 , viscosity is 1.0 cP). It can be seen that the first micro-cantilever plate 2 and the second micro-cantilever plate 4 respectively undergo bending vibrations of specific amplitudes, and the vibration between the dual piezoelectric micro-cantilever plate suspended structures is transmitted through the fluid medium in the vibration coupling gap, and the active bending vibration of the first micro-cantilever plate 2 is coupled to the second micro-cantilever plate 4, so that the second micro-cantilever plate 4 undergoes passive bending vibration, thereby verifying the vibration mode of the dual piezoelectric micro-cantilever plate suspended structure proposed in the present invention.

[0028] Figure 4In the present invention, four different liquids are selected for fluid-solid coupling simulation analysis, including n-heptane, cyclohexane, MD2M, and D4 liquids, and a variation curve between the ratio of the vibration amplitude of the dual piezoelectric micro-cantilever plate suspended structure (the second micro-cantilever plate 4 vibration amplitude / the first micro-cantilever plate 2 vibration amplitude) and the fluid viscosity is obtained. It can be seen that a univariate corresponding relationship between the vibration amplitude ratio of the micro-cantilever plate suspended structure and the fluid viscosity can be established, thereby realizing the measurement of the fluid viscosity, thereby verifying the working mode of the viscosity sensor chip proposed in the present invention.

[0029] In summary, the dual piezoelectric micro-cantilever plate suspension structure in the present invention adopts a free end gap design, and realizes the vibration coupling between the dual piezoelectric micro-cantilever plate suspension structures through the fluid medium, so that the dual piezoelectric micro-cantilever plate suspension structure undergoes active and passive non-resonant bending vibrations; the rectangular protrusion design of the dual piezoelectric micro-cantilever plate suspension structure is used to enhance the vibration transmission effect of the fluid medium, and at the same time to space the piezoelectric electrode pairs, thereby reducing the inhibitory effect of the parasitic effect of the piezoelectric layer on the output amplitude of the sensor chip; the sensor chip adopts locally arranged piezoelectric drive electrodes to excite non-resonant bending vibrations, and the piezoelectric pickup electrodes are used to convert vibration signals into electrical signal outputs through the piezoelectric effect, thereby realizing the self-excitation and self-detection performance of the viscosity sensor chip, which helps to improve the comprehensive measurement performance of the viscosity sensor chip, such as fluid measurement accuracy and stability.

[0030] 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 vibration-coupled dual micro-cantilever plate MEMS viscosity sensor chip, characterized in that: The invention comprises a silicon-based fixed support body (1), a fixed support body cavity (7) being provided on the silicon-based fixed support body (1), a dual piezoelectric micro-cantilever plate suspension structure being provided in the fixed support body cavity (7) on the silicon-based fixed support body (1), the dual piezoelectric micro-cantilever plate suspension structure comprising a first micro-cantilever plate (2) and a second micro-cantilever plate (4) which are rectangular and whose free ends are arranged opposite to each other, a vibration coupling gap (15) being provided between the free end of the first micro-cantilever plate (2) and the free end of the second micro-cantilever plate (4), and the length of the second micro-cantilever plate (4) being less than the length of the first micro-cantilever plate (2); The first micro-cantilever plate (2) is symmetrically provided with a first piezoelectric driving electrode (3-1) and a first piezoelectric vibration pickup electrode (3-2) in its width direction; the second micro-cantilever plate (4) is symmetrically provided with a second piezoelectric driving electrode (5-1) and a second piezoelectric vibration pickup electrode (5-2) in its width direction; the first piezoelectric driving electrode (3-1) and the second piezoelectric vibration pickup electrode (5-1) are located on the same side; the first piezoelectric vibration pickup electrode (3-2) and the second piezoelectric vibration pickup electrode (5-2) are located on the same side; and the first piezoelectric driving electrode (3-1), the first piezoelectric vibration pickup electrode (3-2), the second piezoelectric driving electrode (5-1) and the second piezoelectric vibration pickup electrode (5-2) are all connected to metal leads (6).

2. The vibration-coupled dual micro-cantilever plate MEMS viscosity sensor chip according to claim 1, characterized in that: The first micro-cantilever plate (2) and the second micro-cantilever plate (4) have the same width and thickness; the width of the first micro-cantilever plate (2) is greater than or equal to the length, and the width and length of the first micro-cantilever plate (2) are both more than 5 times the thickness; the width of the second micro-cantilever plate (4) is greater than or equal to the length, and the width and length of the second micro-cantilever plate (4) are both more than 5 times the thickness.

3. A vibration-coupled dual micro-cantilever plate MEMS viscosity sensor chip according to claim 1 or 2, characterized in that: A first rectangular protrusion is provided at the free end of the first micro-cantilever plate (2), a first piezoelectric drive electrode (3-1) and a first piezoelectric pickup electrode (3-2) are symmetrically located on both sides of the first rectangular protrusion, a second rectangular protrusion is provided at the free end of the second micro-cantilever plate (4), a second piezoelectric drive electrode (5-1) and a second piezoelectric pickup electrode (5-2) are symmetrically located on both sides of the second rectangular protrusion, the first rectangular protrusion and the second rectangular protrusion are directly opposite, and a gap is left between the first rectangular protrusion and the second rectangular protrusion.

4. The vibration-coupled dual micro-cantilever plate MEMS viscosity sensor chip according to claim 3, characterized in that: The first micro cantilever plate (2) has the same thickness as the first rectangular protrusion, the second micro cantilever plate (4) has the same thickness as the second rectangular protrusion, and the first rectangular protrusion and the second rectangular protrusion have the same length, width and thickness.

5. The vibration-coupled dual micro-cantilever plate MEMS viscosity sensor chip according to claim 3, characterized in that: The net distance between the first rectangular protrusion and the second rectangular protrusion is 33% to 48% of the width of the vibration coupling gap (15), the width of the first rectangular protrusion is 33% to 36% of the width of the first micro-cantilever plate (2), the width of the second rectangular protrusion is 33% to 36% of the width of the second micro-cantilever plate (4), and the length of the second micro-cantilever plate (4) is 80% to 84% of the length of the first micro-cantilever plate (2).

6. The vibration-coupled dual micro-cantilever MEMS viscosity sensor chip according to claim 1, characterized in that: The first piezoelectric driving electrode (3-1) and the first piezoelectric pickup electrode (3-2) have the same length, width and thickness; the second piezoelectric driving electrode (5-1) and the second piezoelectric pickup electrode (5-2) have the same length, width and thickness.

7. The vibration-coupled dual micro-cantilever plate MEMS viscosity sensor chip according to claim 1, characterized in that: The first piezoelectric driving electrode (3-1), the first piezoelectric vibration pickup electrode (3-2) and the first micro cantilever plate (2) have the same length, and the second piezoelectric driving electrode (5-1), the second piezoelectric vibration pickup electrode (5-2) and the second micro cantilever plate (4) have the same length.

8. The vibration-coupled dual micro-cantilever plate MEMS viscosity sensor chip according to claim 1, characterized in that: The shape of the support body cavity (7) is rectangular, and the symmetry axis of the first micro-cantilever plate (2) and the second micro-cantilever plate (4) in the length direction is coaxial with the symmetry axis of the wide side of the support body cavity (7).

9. The vibration-coupled dual micro-cantilever plate MEMS viscosity sensor chip according to claim 1, characterized in that: The silicon-based solid support (1) comprises a single crystal silicon substrate (8), the bottom and top surfaces of the single crystal silicon substrate (8) are both provided with a thermally oxidized silicon film (9), the surface of the thermally oxidized silicon film (9) on the top surface of the single crystal silicon substrate (8) is provided with a piezoelectric layer bottom electrode molybdenum film (10), the surface of the piezoelectric layer bottom electrode molybdenum film (10) is provided with a low-stress aluminum nitride piezoelectric film (11), and the surface of the low-stress aluminum nitride piezoelectric film (11) is provided with an electrode metal layer (11) used as a first piezoelectric driving electrode (3-1), a first piezoelectric pickup electrode (3-2), a second piezoelectric driving electrode (5-1) and a second piezoelectric pickup electrode (5-2) 12), a silicon nitride film (14) is provided on the surface of the low stress aluminum nitride piezoelectric film (11) and the electrode metal layer (12); the first micro cantilever plate (2), the second micro cantilever plate (4) and the silicon-based solid support body (1) share the thermally oxidized silicon film (9) on the top surface of the single crystal silicon substrate (8), the molybdenum film (10) at the bottom electrode of the piezoelectric layer, the low stress aluminum nitride piezoelectric film (11), the silicon nitride film (14) and part of the single crystal silicon substrate (8), wherein the single crystal silicon substrate (8) on the first micro cantilever plate (2) and the second micro cantilever plate (4) is thinner than the single crystal silicon substrate (8) of the silicon-based solid support body (1).

10. The working method of a vibration-coupled dual micro-cantilever plate MEMS viscosity sensor chip according to any one of claims 1 to 9, characterized in that: include: When the vibration-coupled dual micro-cantilever plate MEMS viscosity sensor chip is immersed in a fluid, the fluid fills the vibration coupling gap (15) and acts as a vibration coupling medium; The first micro-cantilever plate (2) is used as an active cantilever plate. When an alternating electric field is applied to a first piezoelectric driving electrode (3-1) of the first micro-cantilever plate (2), a top electrode of the piezoelectric layer of the first micro-cantilever plate (2) is energized and a bottom electrode is grounded, so that the first micro-cantilever plate (2) generates non-resonant bending vibration at the frequency of the driving voltage, and simultaneously drives the fluid around the first micro-cantilever plate (2) to generate corresponding vibration. The second micro-cantilever plate (4) is used as a passive cantilever plate, and generates a vibration coupling effect with the first cantilever plate (2) through a fluid medium, and the fluid medium in the vibration coupling gap (15) is in the first The micro-cantilever plate (2) and the second micro-cantilever plate (4) are subjected to shear force, so that the vibration amplitude of the second micro-cantilever plate (4) is directly related to the fluid viscosity and the vibration amplitude of the first micro-cantilever plate (2); when the first micro-cantilever plate (2) and the second micro-cantilever plate (4) are in a non-resonant bending vibration state, the first piezoelectric vibration pickup electrode (3-2) and the second piezoelectric vibration pickup electrode (5-2) form a top electrode externally connected to an electrical output port and a bottom electrode grounded, and an alternating voltage detection signal is generated and output through the piezoelectric effect, thereby extracting the output voltage ratio of the dual piezoelectric micro-cantilever plate suspended structure to achieve fluid viscosity measurement.

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