CN113091993A - Multistage cantilever beam structure and bionic differential pressure sensor thereof - Google Patents
Multistage cantilever beam structure and bionic differential pressure sensor thereof Download PDFInfo
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- CN113091993A CN113091993A CN202110307482.5A CN202110307482A CN113091993A CN 113091993 A CN113091993 A CN 113091993A CN 202110307482 A CN202110307482 A CN 202110307482A CN 113091993 A CN113091993 A CN 113091993A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
- G01L13/00—Devices or apparatus for measuring differences of two or more fluid pressure values
- G01L13/06—Devices or apparatus for measuring differences of two or more fluid pressure values using electric or magnetic pressure-sensitive elements
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B81—MICROSTRUCTURAL TECHNOLOGY
- B81B—MICROSTRUCTURAL DEVICES OR SYSTEMS, e.g. MICROMECHANICAL DEVICES
- B81B7/00—Microstructural systems; Auxiliary parts of microstructural devices or systems
- B81B7/02—Microstructural systems; Auxiliary parts of microstructural devices or systems containing distinct electrical or optical devices of particular relevance for their function, e.g. microelectro-mechanical systems [MEMS]
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B81—MICROSTRUCTURAL TECHNOLOGY
- B81B—MICROSTRUCTURAL DEVICES OR SYSTEMS, e.g. MICROMECHANICAL DEVICES
- B81B2201/00—Specific applications of microelectromechanical systems
- B81B2201/02—Sensors
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B81—MICROSTRUCTURAL TECHNOLOGY
- B81B—MICROSTRUCTURAL DEVICES OR SYSTEMS, e.g. MICROMECHANICAL DEVICES
- B81B2201/00—Specific applications of microelectromechanical systems
- B81B2201/02—Sensors
- B81B2201/0264—Pressure sensors
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B81—MICROSTRUCTURAL TECHNOLOGY
- B81B—MICROSTRUCTURAL DEVICES OR SYSTEMS, e.g. MICROMECHANICAL DEVICES
- B81B2203/00—Basic microelectromechanical structures
- B81B2203/01—Suspended structures, i.e. structures allowing a movement
- B81B2203/0118—Cantilevers
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Abstract
The invention discloses a multistage cantilever beam structure, which comprises a primary main beam, a plurality of secondary side beams and a plurality of tertiary auxiliary beams, wherein the primary main beam is provided with a plurality of first-stage main beams; the secondary side beams are connected with the primary main beam, the plurality of secondary side beams are symmetrically distributed on two sides of the primary main beam, and the secondary side beams are perpendicular to the primary main beam; the three-level auxiliary beams are connected with the two-level side beams, the three-level auxiliary beams are symmetrically distributed on two sides of the two-level side beams, and the three-level auxiliary beams are perpendicular to the two-level side beams; the rigidity of the secondary side beam is smaller than that of the primary main beam, and the multi-stage cantilever beam structure is applied to the bionic differential pressure sensor, so that the effects of high sensitivity of the sensor under low differential pressure and large measuring range of the sensor under high differential pressure are achieved.
Description
Technical Field
The invention relates to the field of micro-mechanical electronic gas differential pressure measurement, in particular to a multi-stage cantilever beam structure and a bionic differential pressure sensor thereof.
Background
Micro-Electro-Mechanical systems (MEMS) differential pressure sensors are widely used in the fields of aerospace and central air conditioning systems due to their advantages of small size, low cost, mass production, high performance, etc. At present, two MEMS differential pressure sensors, namely a film type MEMS differential pressure sensor and a cantilever beam type MEMS differential pressure sensor, are available, and under the same differential pressure action, the cantilever beam can generate larger bending deformation, namely has higher sensitivity, because the three ends of the cantilever beam are free ends. Therefore, for the measurement of micro differential pressure, the cantilever type MEMS differential pressure sensor has more superiority, however, when a larger pressure difference is measured, the characteristic that the cantilever beam is easier to bend and deform can reach the saturation of the bending degree more quickly, therefore, the range of the cantilever beam type MEMS differential pressure sensor is smaller, the range can be increased by reducing the stress area of the single-stage cantilever beam, because the pressure differential required is greater when the force applied to the cantilever beam is the same when the force area is smaller, therefore, the measuring range can be increased by reducing the stress area, the stress area of the single-stage cantilever beam is further reduced by reducing the size of the single-stage cantilever beam in the prior art, thereby improving the measuring range, but at the same time, the sensitivity of the single-stage cantilever beam is reduced when measuring low differential pressure, therefore, the double improvement of the two indexes of the sensitivity and the measuring range of the sensor cannot be realized only by changing the size of the single-stage cantilever beam.
Disclosure of Invention
The invention aims to provide a multi-stage cantilever beam structure and a bionic differential pressure sensor thereof, and aims to solve the problem that double improvement of two indexes of sensitivity and measuring range of a sensor cannot be realized only by changing the size of a single-stage cantilever beam in the prior art.
In order to achieve the purpose, the invention provides the following scheme:
a multi-level cantilever beam structure comprising: a primary main beam, a plurality of secondary side beams, and a plurality of tertiary auxiliary beams;
the secondary side beams are connected with the primary main beam, a plurality of secondary side beams are symmetrically distributed on two sides of the primary main beam, and the secondary side beams are perpendicular to the primary main beam; the three-level auxiliary beams are connected with the two-level side beams, a plurality of the three-level auxiliary beams are symmetrically distributed on two sides of the two-level side beams, and the three-level auxiliary beams are perpendicular to the two-level side beams; the rigidity of the secondary side beam is smaller than that of the primary main beam.
A bionic differential pressure sensor based on a multistage cantilever beam structure comprises: the sensor comprises an upper pressure guide port, an upper packaging cavity, a sensing diaphragm, a lower packaging cavity, an external signal lead, a lower pressure guide port, a reference resistor, a signal lead, a piezoresistive unit and a multistage cantilever beam structure; the multistage cantilever beam structure comprises a primary main beam, a plurality of secondary side beams and a plurality of tertiary auxiliary beams; the secondary side beams are connected with the primary main beam, a plurality of secondary side beams are symmetrically distributed on two sides of the primary main beam, and the secondary side beams are perpendicular to the primary main beam; the plurality of tertiary auxiliary beams are symmetrically distributed on two sides of the secondary side beam; the rigidity of the secondary side beam is less than that of the primary main beam;
the sensing diaphragm is positioned in the middle of a sealed cavity formed by the upper packaging cavity and the lower packaging cavity, and the reference resistor, the signal lead, the piezoresistive unit and the multistage cantilever beam structure are all positioned on the sensing diaphragm and are all in contact with the sensing diaphragm; the piezoresistive units are connected with the root parts of the multi-stage cantilever beam structures; the signal lead is respectively connected with the reference resistor and the piezoresistive unit and is used for outputting resistance signals of the reference resistor and the piezoresistive unit; the external signal lead is connected with the signal lead and arranged on the lower packaging cavity; the upper pressure guide port is connected with the upper packaging cavity; the lower pressure guide port is connected with the lower packaging cavity;
the multi-stage cantilever beam structure is characterized in that a first gas pressure enters the upper packaging cavity through the upper pressure guide port, a second gas pressure enters the lower packaging cavity through the lower pressure guide port, the first gas pressure and the second gas pressure form pressure difference on the upper side and the lower side of the sensing diaphragm, the multi-stage cantilever beam structure generates bending deformation under the action of the pressure difference and generates strain on the root part, the pressure resistance unit generates a resistance value signal according to the strain, the signal lead outputs the resistance value signal through the external signal lead, and the relation between the pressure difference and the resistance value signal is obtained according to the pressure difference and the resistance value signal.
Optionally, the sensing membrane and the multi-stage cantilever beam structure are made of resin; the piezoresistive units and the reference resistor are made of monocrystalline silicon.
Optionally, the sensing diaphragm and the multi-stage cantilever structure are made of photoresist, and the piezoresistive unit and the reference resistor are made of constantan, platinum or gold formed by sputtering.
Optionally, the sensing diaphragm and the multi-stage cantilever beam structure have the same thickness, and the thickness is greater than or equal to 3 microns and less than 50 microns.
Optionally, the width of the tertiary auxiliary beam is less than or equal to 5 micrometers; and the gaps of the three-level auxiliary beams are less than or equal to 5 micrometers.
Optionally, the length of the primary main beam is more than 2 times the width of the primary main beam, and the width of the primary main beam is not less than 100 micrometers.
Optionally, the length of the secondary side beam is not less than the width of the primary main beam, and the width of the secondary side beam is not less than 5 microns.
Optionally, the manufacturing process of the sensing diaphragm is as follows: sputtering 100 nm of metal chromium and 100 nm of metal aluminum on a silicon chip as a chromium/aluminum sacrificial layer; spin-coating polyimide photoresist or SU-8 photoresist on the sacrificial chromium/aluminum layer, and patterning to obtain a cantilever beam structure; spin-coating photoresist and patterning the photoresist to be used as a mask for sputtering the piezoresistive unit and the reference resistor in the next step; sputtering a chromium/constantan layer to serve as the piezoresistive unit and the reference resistor and removing glue; spin-coating the photoresist and patterning the photoresist to be used as a mask for sputtering the signal lead in the next step; sputtering a chromium/gold layer to serve as the signal lead and removing glue; and removing the chromium/aluminum sacrificial layer by using an electrolysis mode, and peeling the sensing diaphragm from the silicon wafer integrally.
Optionally, the manufacturing process of the sensing diaphragm is as follows: sputtering 100 nm of metal chromium and 100 nm of metal aluminum on a silicon chip as a chromium/aluminum sacrificial layer; spin-coating polyimide or PET on the sacrificial chromium/aluminum layer, and patterning the multilevel cantilever beam structure by reactive ion etching; spin-coating photoresist and patterning the photoresist to be used as a mask for sputtering the piezoresistive unit and the reference resistor in the next step; sputtering a chromium/platinum layer as the piezoresistive unit and the reference resistor and removing glue; spin-coating photoresist and patterning the photoresist to be used as a mask for sputtering the signal lead in the next step; sputtering a chromium/gold layer to serve as the signal lead and removing glue; and removing the chromium/aluminum sacrificial layer by using an electrolysis mode, and peeling the sensing diaphragm from the silicon wafer integrally.
According to the specific embodiment provided by the invention, the invention discloses the following technical effects:
the invention discloses a multistage cantilever beam structure and a bionic pressure difference sensor thereof, wherein a comb-shaped wing configuration-imitated multistage cantilever beam structure is adopted to replace a common cantilever beam structure, and the difference of bending rigidity between a secondary side beam and a primary main beam is utilized to realize that: under low pressure difference, the multi-stage cantilever beam structure is smaller in stress area than a common single-stage cantilever beam structure, but larger viscous force can be generated due to the existence of the three-stage auxiliary beam, so that the sensitivity similar to that of the common single-stage cantilever beam can be realized; under high pressure difference, the rigidity of the secondary side beam is smaller, so that larger bending deformation is generated, and the multistage cantilever beam structure has a smaller stress area than the common single-stage cantilever beam structure, so that smaller sensitivity can be realized to increase the measurement range.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed to be used in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings without inventive exercise.
FIG. 1 is a schematic view of a measurement principle of a cantilever-beam-based differential pressure sensor provided by the invention;
FIG. 2 is an optical view of a comb-shaped wing of a miniature insect named Thysanopterus fasciatus according to the present invention;
FIG. 3 is a diagram showing simulation results of the blocking effect of the comb-shaped wings on the air flow at a low Reynolds number according to the present invention;
FIG. 4 is a schematic view of a multi-stage cantilever structure designed to simulate a comb-shaped wing according to the present invention;
FIG. 5 is a schematic diagram of a conventional single-stage cantilever structure provided by the present invention;
FIG. 6(a) is a diagram of a deformation result of a multi-stage cantilever structure in a bidirectional fluid-solid coupling simulation calculation under a pressure difference of 5 Pa;
FIG. 6(b) is a diagram showing the deformation result of the single-stage cantilever structure in the bidirectional fluid-solid coupling simulation calculation under a pressure difference of 5 Pa;
FIG. 7(a) is a diagram of a deformation result of a multi-stage cantilever structure in a bidirectional fluid-solid coupling simulation calculation under a pressure difference of 500 Pa;
FIG. 7(b) is a diagram of a deformation result of a single-stage cantilever structure in a bidirectional fluid-solid coupling simulation calculation under a pressure difference of 500 Pa;
FIG. 8(a) is a diagram showing a deformation result of a multi-stage cantilever structure in a bidirectional fluid-solid coupling simulation calculation under a pressure difference of 1000 Pa;
FIG. 8(b) is a diagram showing the deformation result of the single-stage cantilever structure in the bidirectional fluid-solid coupling simulation calculation under a pressure difference of 1000 Pa;
FIG. 9 is a schematic structural diagram of a biomimetic differential pressure sensor based on a multi-stage cantilever structure according to the present invention;
FIG. 10 is an external view of a bionic differential pressure sensor based on a multi-stage cantilever structure according to the present invention;
FIG. 11 is a schematic diagram of a processing route of a biomimetic differential pressure sensor based on a multi-level cantilever structure according to the present invention;
FIG. 12 is a graph showing the results of measurements of sensors based on type II cantilevers and type I cantilevers according to the present invention under different pressure differentials.
Description of the symbols: the sensor comprises an upper pressure guide port 1, an upper packaging cavity 2, a sensing diaphragm 3, a lower packaging cavity 4, an external signal lead 5, a lower pressure guide port 6, a reference resistor 7, a signal lead 8, a piezoresistive unit 9, a multistage cantilever beam structure 10, a tertiary auxiliary beam 11, a secondary side beam 12, a primary main beam 13, a silicon wafer 14, a chromium/aluminum sacrificial layer 15, a polyimide photoresist 16, a chromium/constantan layer 17, a chromium/gold layer 18 and a gap 19 of the tertiary auxiliary beam.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The invention aims to provide a multi-stage cantilever beam structure and a bionic differential pressure sensor thereof, and aims to solve the problem that double improvement of two indexes of sensitivity and measuring range of a sensor cannot be realized only by changing the size of a single-stage cantilever beam in the prior art.
Many technical problems in the engineering field can be skillfully solved from the biology world, the size of the cantilever beam in the existing cantilever beam type differential pressure sensor (the measurement principle is shown in figure 1) is very similar to the size of the wings of a group of ubiquitous micro insects existing in the biology world, and the wings of the micro insects are transformed into a unique comb-shaped wing configuration shown in figure 2, so that the precious bionic sense is provided for the design of a new cantilever beam configuration. Studies have shown that at low reynolds numbers (Re <80), the comb-wing configuration can be seen as a continuous plane (as shown in fig. 3) due to the effects of air viscous forces and boundary layer effects, which is comparable to the aerodynamic forces generated by conventional membrane wing configurations. The invention designs a multi-stage cantilever beam structure imitating the comb-shaped wing structure as shown in figure 4 by using the comb-shaped wing structure as inspiration.
Fig. 5 is a general single-stage cantilever beam structure, and through utilizing a bidirectional fluid-solid coupling simulation analysis, the deformation of the multi-stage cantilever beam structure 10 in fig. 4 and the deformation of the single-stage cantilever beam structure in fig. 5 under the differential pressure of 5Pa, 500Pa and 1000Pa are calculated in a simulation mode, and as a result, as shown in fig. 6-8, the feasibility of the measurement principle is proved, wherein the general single-stage cantilever beam structure mentioned in the present invention is the ii-type cantilever beam in fig. 5, and the multi-stage cantilever beam structure is the i-type cantilever beam in fig. 4.
In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in further detail below.
As shown in fig. 4, a multi-stage cantilever beam structure 10 includes: a primary main beam 13, secondary side beams 12, and tertiary auxiliary beams 11; the secondary side beams 12 are connected with the primary main beam 13, a plurality of secondary side beams 12 are symmetrically distributed on two sides of the primary main beam 13, and the secondary side beams 12 are perpendicular to the primary main beam 13; the tertiary auxiliary beams 11 are connected with the secondary side beams 12, a plurality of the tertiary auxiliary beams 11 are symmetrically distributed on two sides of the secondary side beams 12, and the tertiary auxiliary beams 11 are perpendicular to the secondary side beams 12; the rigidity of the secondary side member 12 is smaller than that of the primary main member 13.
As shown in fig. 9-10, the present invention further provides a biomimetic differential pressure sensor based on a multi-stage cantilever structure 10, comprising: the sensor comprises an upper pressure guide port 1, an upper packaging cavity 2, a sensing diaphragm 3, a lower packaging cavity 4, an external signal lead 5, a lower pressure guide port 6, a reference resistor 7, a signal lead 8, a piezoresistive unit 9 and a multistage cantilever beam structure 10; the multi-stage cantilever beam structure 10 comprises a primary main beam 13, a plurality of secondary side beams 12 and a plurality of tertiary auxiliary beams 11; the secondary side beams 12 are connected with the primary main beam 13, a plurality of secondary side beams 12 are symmetrically distributed on two sides of the primary main beam 13, and the secondary side beams 12 are perpendicular to the primary main beam 13; the plurality of tertiary auxiliary beams 11 are symmetrically distributed on two sides of the secondary side beam 12; the rigidity of the secondary side member 12 is smaller than that of the primary main member 13.
The sensing diaphragm 3 is located in the middle of a sealed cavity formed by the upper packaging cavity 2 and the lower packaging cavity 4, and the reference resistor 7, the signal lead 8, the piezoresistive unit 9 and the multi-stage cantilever beam structure 10 are all located on the sensing diaphragm 3 and are all in contact with the sensing diaphragm 3; the piezoresistive units 9 are connected with the root parts of the multi-stage cantilever beam structures 10; the signal lead 8 is respectively connected to the reference resistor 7 and the piezoresistive unit 9, and the signal lead 8 is used for outputting resistance signals of the reference resistor 7 and the piezoresistive unit 9; the external signal lead 5 is connected with the signal 8 lead and arranged on the lower packaging cavity 4; the upper pressure guide port 1 is connected with the upper packaging cavity 2; the lower pressure guide port 6 is connected with the lower packaging cavity 4.
The first gas pressure enters the upper packaging cavity 2 through the upper pressure guide port 1, the second gas pressure enters the lower packaging cavity 4 through the lower pressure guide port 6, pressure differences are formed between the first gas pressure and the second gas pressure at the upper side and the lower side of the sensing diaphragm 3, the multi-stage cantilever beam structure 10 generates bending deformation under the action of the pressure differences and generates strain at the root part, the pressure resistance unit 9 generates a resistance value signal according to the strain, the signal lead 8 outputs the resistance value signal through the external signal lead 5, and the relation between the pressure differences and the resistance value signal is obtained according to the pressure differences and the resistance value signal.
In practical applications, the sensing diaphragm 3 and the multi-stage cantilever structure 10 are made of resin, such as polyimide, pet (polyethylene terephthalate), parylene, and the piezoresistive unit 9 and the reference resistor 7 are made of monocrystalline silicon.
In practical application, the sensing diaphragm 3 and the multi-stage cantilever structure 10 are made of photoresist, the piezoresistive unit 9 and the reference resistor 7 are made of constantan, platinum or gold formed by sputtering, and the photoresist is SU-8 photoresist capable of being etched by light. The SU-8 photoresist is an epoxy type, near ultraviolet negative photoresist.
In practical application, the thickness of the sensing diaphragm 3 is the same as that of the multi-stage cantilever structure 10, and the thickness is greater than or equal to 3 micrometers and less than 50 micrometers.
In practical application, the width of the tertiary auxiliary beam 11 is less than or equal to 5 micrometers; the gaps 19 of the plurality of tertiary auxiliary beams 11 are less than or equal to 5 micrometers.
In practical application, the length of the primary main beam 13 is more than 2 times of the width of the primary main beam 13, and the width of the primary main beam 13 is not less than 100 micrometers.
In practical applications, the length of the secondary side member 12 is not less than the width of the primary main member 13, and the width of the secondary side member 12 is not less than 5 μm.
In practical application, the manufacturing process of the sensing diaphragm 3 is as follows: sputtering 100 nm of metal chromium and 100 nm of metal aluminum on a silicon chip as a chromium/aluminum sacrificial layer; spin-coating polyimide photoresist or SU-8 photoresist on the sacrificial chromium/aluminum layer, and patterning to obtain a cantilever beam structure; spin-coating photoresist and patterning the photoresist to be used as a mask for sputtering the piezoresistive unit 9 and the reference resistor 7 in the next step; sputtering a chromium/constantan layer to serve as the piezoresistive unit 9 and the reference resistor 7, and removing glue; spin-coating the photoresist and patterning the photoresist to be used as a mask for sputtering the signal lead in the next step; sputtering a chromium/gold layer to serve as the signal lead and removing glue; and removing the chromium/aluminum sacrificial layer by using an electrolytic method, and peeling the sensing diaphragm 3 from the silicon wafer integrally.
In practical application, the manufacturing process of the sensing diaphragm 3 is as follows: sputtering 100 nm of metal chromium and 100 nm of metal aluminum on a silicon chip as a chromium/aluminum sacrificial layer; spin-coating polyimide or PET on the sacrificial chromium/aluminum layer, and patterning the multilevel cantilever beam structure 10 by reactive ion etching; spin-coating photoresist and patterning the photoresist to be used as a mask for sputtering the piezoresistive unit 9 and the reference resistor 7 in the next step; sputtering a chromium/platinum layer as the piezoresistive unit 9 and the reference resistor 7 and removing glue; spin-coating photoresist and patterning the photoresist to be used as a mask for sputtering the signal lead in the next step; sputtering a chromium/gold layer to serve as the signal lead and removing glue; and removing the chromium/aluminum sacrificial layer by using an electrolytic method, and peeling the sensing diaphragm 3 from the silicon wafer integrally.
The technical scheme provided by the invention is combined into practical application, and the invention provides a specific implementation scheme of the differential pressure sensor with the multi-stage cantilever beam structure, which comprises the following steps:
as shown in fig. 10, a bionic differential pressure sensor based on a multi-stage cantilever structure includes an upper pressure guide port 1, an upper package cavity 2, a sensing diaphragm 3, a lower package cavity 4, an external signal lead 5, a lower pressure guide port 6, a reference resistor 7, a signal lead 8, a piezoresistive unit 9, and a multi-stage cantilever structure 10; the sensing diaphragm 3 is packaged between the upper packaging cavity 2 and the lower packaging cavity 4, the sensing diaphragm 3 is embedded in a groove in the lower packaging cavity 4, a multi-stage cantilever beam structure 10 is arranged on the sensing diaphragm 3, and the multi-stage cantilever beam structure 10 is composed of a first-stage main beam 13, a second-stage side beam 12 and a third-stage auxiliary beam 11. The secondary side beam 12 structures are positioned on two sides of the primary main beam 13 and are symmetrically distributed, and the tertiary auxiliary beam 11 structures are positioned on two sides of the secondary side beam 12 and are symmetrically distributed; the length of the first-level main beam is 450 micrometers, and the width of the first-level main beam is 200 micrometers; a secondary side beam having a length of 250 microns and a width of 8 microns; the third class auxiliary beam, length is 50 microns, and the width is 5 microns, and clearance 19 is 5 microns. The multi-stage cantilever beam structure 10 on the sensing diaphragm 3 is located in the middle of the cavities of the upper packaging cavity 2 and the lower packaging cavity 4. The signal lead 8 is fixed to the sensor diaphragm 3, and is connected to the piezoresistive unit 9 and the reference resistor 7, and resistance value signals of the piezoresistive unit 9 and the reference resistor 7 are output from the signal lead 8. The signal lead 8 is connected with the external signal lead 5 through the conductive silver adhesive and the wire. The sensing diaphragm 3 and the multi-stage cantilever structure 10 are made of polyimide photoresist and have a thickness of 4 microns, and the reference resistor 7 and the piezoresistive unit 9 are made of constantan (Cu 55 wt% and Ni 45 wt%) and have a thickness of 30 nanometers. The upper packaging cavity 2 and the lower packaging cavity 4 are obtained by 3-D printing of photosensitive resin materials. The reference resistor and the piezoresistive unit are connected with the signal lead and are arranged on the sensing diaphragm 3.
The bionic pressure difference sensor based on the multistage cantilever beam structure converts the physical information of gas pressure difference into strain of the root of the cantilever beam by utilizing the cantilever beam structure, and then converts the strain into an electric signal to be acquired through the change of the piezoresistive resistance value of the root, and the specific working principle is as follows: the external gas pressure enters the upper packaging cavity 2 and the lower packaging cavity 4 through the upper pressure guide port 1 and the lower pressure guide port 6, and pressure difference is formed between the upper side and the lower side of the sensing diaphragm 3. Under the action of the pressure difference, the cantilever beam structure 10 on the sensing diaphragm 3 is bent and deformed, the strain generated at the root of the cantilever beam structure is converted into an electric signal by the piezoresistive unit 9 and is output by the signal lead 8, and finally the relation between the pressure difference and the output electric signal is obtained. The common single-stage cantilever beam structure is replaced by the comb-shaped wing-like-structure-imitated multi-stage cantilever beam structure 10, and the difference of the bending rigidity between a second-stage side beam 12 and a first-stage main beam 13 is utilized to realize that: under low pressure difference, the multi-stage cantilever beam structure 10 has a smaller stress area than a common single-stage cantilever beam structure, but due to the existence of the three-stage auxiliary beam 11, a larger viscous force can be generated, so that the sensitivity similar to that of the common single-stage cantilever beam can be realized; under high pressure difference, the secondary side beam 12 has lower rigidity and thus generates larger bending deformation, resulting in a smaller stressed area of the multi-stage cantilever beam structure 10 than that of a common single-stage cantilever beam structure, and therefore, smaller sensitivity can be realized to increase the measurement range. Finally, the single-stage cantilever beam structure is realized, and the practical application requirement of a larger range can be met while the characteristic of high sensitivity under low pressure difference is kept.
The processing process flow of the bionic differential pressure sensor based on the multi-stage cantilever beam structure is shown in figure 11. Sputtering 100 nm of chromium metal and 100 nm of aluminum metal on a silicon wafer 14 as a sacrificial layer 15; spinning polyimide photoresist 16 with the thickness of 4 microns on the chromium/aluminum sacrificial layer, and patterning to form a cantilever beam structure; spin-coating photoresist and patterning the photoresist to be used as a mask for sputtering the piezoresistive unit and the reference resistor in the next step; sputtering a chromium/constantan layer 17 as a piezoresistive unit and a reference resistor and removing glue; spin-coating photoresist and patterning the photoresist to be used as a mask for sputtering a signal lead in the next step; sputtering a chromium/gold layer 18 as a signal lead and removing the glue; and removing the sacrificial layer 15 by using an electrolytic mode, and peeling the sensing diaphragm from the silicon wafer integrally.
FIG. 12 shows the test results of the sensors based on the II-type cantilever beam and the I-type cantilever beam under different pressure differences, and it can be seen from the graph that the resistance change rates of the two sensors are obviously changed at the time of low pressure difference, i.e. the two sensors have better sensitivity; when the pressure difference is measured, along with the increase of the pressure difference, it can be obviously seen that the resistance change rate of the sensor based on the I-type cantilever beam is obviously lower than that of the sensor based on the II-type cantilever beam, namely, compared with the sensor based on the II-type cantilever beam, the measuring range of the sensor based on the I-type cantilever beam is larger.
The embodiments in the present description are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments are referred to each other.
The principles and embodiments of the present invention have been described herein using specific examples, which are provided only to help understand the method and the core concept of the present invention; meanwhile, for a person skilled in the art, according to the idea of the present invention, the specific embodiments and the application range may be changed. In view of the above, the present disclosure should not be construed as limiting the invention.
Claims (10)
1. A multi-stage cantilever beam structure, comprising: a primary main beam, a plurality of secondary side beams, and a plurality of tertiary auxiliary beams;
the secondary side beams are connected with the primary main beam, a plurality of secondary side beams are symmetrically distributed on two sides of the primary main beam, and the secondary side beams are perpendicular to the primary main beam; the three-level auxiliary beams are connected with the two-level side beams, a plurality of the three-level auxiliary beams are symmetrically distributed on two sides of the two-level side beams, and the three-level auxiliary beams are perpendicular to the two-level side beams; the rigidity of the secondary side beam is smaller than that of the primary main beam.
2. The utility model provides a bionical differential pressure sensor based on multistage cantilever beam structure which characterized in that includes: the sensor comprises an upper pressure guide port, an upper packaging cavity, a sensing diaphragm, a lower packaging cavity, an external signal lead, a lower pressure guide port, a reference resistor, a signal lead, a piezoresistive unit and a multistage cantilever beam structure; the multistage cantilever beam structure comprises a primary main beam, a plurality of secondary side beams and a plurality of tertiary auxiliary beams; the secondary side beams are connected with the primary main beam, a plurality of secondary side beams are symmetrically distributed on two sides of the primary main beam, and the secondary side beams are perpendicular to the primary main beam; the plurality of tertiary auxiliary beams are symmetrically distributed on two sides of the secondary side beam; the rigidity of the secondary side beam is less than that of the primary main beam;
the sensing diaphragm is positioned in the middle of a sealed cavity formed by the upper packaging cavity and the lower packaging cavity, and the reference resistor, the signal lead, the piezoresistive unit and the multistage cantilever beam structure are all positioned on the sensing diaphragm and are all in contact with the sensing diaphragm; the piezoresistive units are connected with the root parts of the multi-stage cantilever beam structures; the signal lead is respectively connected with the reference resistor and the piezoresistive unit and is used for outputting resistance signals of the reference resistor and the piezoresistive unit; the external signal lead is connected with the signal lead and arranged on the lower packaging cavity; the upper pressure guide port is connected with the upper packaging cavity; the lower pressure guide port is connected with the lower packaging cavity;
the multi-stage cantilever beam structure is characterized in that a first gas pressure enters the upper packaging cavity through the upper pressure guide port, a second gas pressure enters the lower packaging cavity through the lower pressure guide port, the first gas pressure and the second gas pressure form pressure difference on the upper side and the lower side of the sensing diaphragm, the multi-stage cantilever beam structure generates bending deformation under the action of the pressure difference and generates strain on the root part, the pressure resistance unit generates a resistance value signal according to the strain, the signal lead outputs the resistance value signal through the external signal lead, and the relation between the pressure difference and the resistance value signal is obtained according to the pressure difference and the resistance value signal.
3. The bionic differential pressure sensor based on the multistage cantilever beam structure is characterized in that the sensing membrane and the multistage cantilever beam structure are made of resin; the piezoresistive units and the reference resistor are made of monocrystalline silicon.
4. The bionic differential pressure sensor based on the multistage cantilever beam structure as claimed in claim 2, wherein the sensing diaphragm and the multistage cantilever beam structure are made of photoresist, and the piezoresistive unit and the reference resistor are made of constantan, platinum or gold formed by sputtering.
5. The biomimetic pressure differential sensor based on the multi-stage cantilever beam structure of claim 2, wherein the sensing membrane has the same thickness as the multi-stage cantilever beam structure, and the thickness is greater than or equal to 3 microns and less than 50 microns.
6. The biomimetic pressure differential sensor based on the multi-stage cantilever beam structure according to claim 2, wherein the width of the third-stage auxiliary beam is less than or equal to 5 microns; and the gaps of the three-level auxiliary beams are less than or equal to 5 micrometers.
7. The bionic differential pressure sensor based on the multistage cantilever beam structure is characterized in that the length of the primary main beam is more than 2 times of the width of the primary main beam, and the width of the primary main beam is not less than 100 micrometers.
8. The biomimetic pressure differential sensor based on a multi-stage cantilever beam structure of claim 2, wherein the length of the secondary side beam is not less than the width of the primary main beam, and the width of the secondary side beam is not less than 5 microns.
9. The bionic differential pressure sensor based on the multistage cantilever beam structure as claimed in claim 2, wherein the manufacturing process of the sensing diaphragm is as follows: sputtering 100 nm of metal chromium and 100 nm of metal aluminum on a silicon chip as a chromium/aluminum sacrificial layer; spin-coating polyimide photoresist or SU-8 photoresist on the sacrificial chromium/aluminum layer, and patterning to obtain a cantilever beam structure; spin-coating photoresist and patterning the photoresist to be used as a mask for sputtering the piezoresistive unit and the reference resistor in the next step; sputtering a chromium/constantan layer to serve as the piezoresistive unit and the reference resistor and removing glue; spin-coating the photoresist and patterning the photoresist to be used as a mask for sputtering the signal lead in the next step; sputtering a chromium/gold layer to serve as the signal lead and removing glue; and removing the chromium/aluminum sacrificial layer by using an electrolysis mode, and peeling the sensing diaphragm from the silicon wafer integrally.
10. The bionic differential pressure sensor based on the multistage cantilever beam structure as claimed in claim 2, wherein the manufacturing process of the sensing diaphragm is as follows: sputtering 100 nm of metal chromium and 100 nm of metal aluminum on a silicon chip as a chromium/aluminum sacrificial layer; spin-coating polyimide or PET on the sacrificial chromium/aluminum layer, and patterning the multilevel cantilever beam structure by reactive ion etching; spin-coating photoresist and patterning the photoresist to be used as a mask for sputtering the piezoresistive unit and the reference resistor in the next step; sputtering a chromium/platinum layer as the piezoresistive unit and the reference resistor and removing glue; spin-coating photoresist and patterning the photoresist to be used as a mask for sputtering the signal lead in the next step; sputtering a chromium/gold layer to serve as the signal lead and removing glue; and removing the chromium/aluminum sacrificial layer by using an electrolysis mode, and peeling the sensing diaphragm from the silicon wafer integrally.
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