CN114427879B - MEMS respiration monitoring sensing chip, preparation method and sensor assembly - Google Patents
MEMS respiration monitoring sensing chip, preparation method and sensor assembly Download PDFInfo
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- CN114427879B CN114427879B CN202110171845.7A CN202110171845A CN114427879B CN 114427879 B CN114427879 B CN 114427879B CN 202110171845 A CN202110171845 A CN 202110171845A CN 114427879 B CN114427879 B CN 114427879B
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- 238000012544 monitoring process Methods 0.000 title claims abstract description 43
- 230000029058 respiratory gaseous exchange Effects 0.000 title claims abstract description 41
- 238000002360 preparation method Methods 0.000 title abstract description 6
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 claims abstract description 56
- 230000000241 respiratory effect Effects 0.000 claims abstract description 36
- 239000001569 carbon dioxide Substances 0.000 claims abstract description 28
- 229910002092 carbon dioxide Inorganic materials 0.000 claims abstract description 28
- 238000000034 method Methods 0.000 claims abstract description 16
- 230000008859 change Effects 0.000 claims abstract description 13
- 230000008569 process Effects 0.000 claims abstract description 7
- 239000000758 substrate Substances 0.000 claims description 29
- 238000002161 passivation Methods 0.000 claims description 17
- 229910052751 metal Inorganic materials 0.000 claims description 9
- 239000002184 metal Substances 0.000 claims description 9
- 238000009413 insulation Methods 0.000 claims description 8
- 229910021420 polycrystalline silicon Inorganic materials 0.000 claims description 7
- 229920005591 polysilicon Polymers 0.000 claims description 7
- 238000005070 sampling Methods 0.000 claims description 7
- 239000011159 matrix material Substances 0.000 claims description 6
- 229910052581 Si3N4 Inorganic materials 0.000 claims description 5
- 238000004891 communication Methods 0.000 claims description 5
- 238000000151 deposition Methods 0.000 claims description 5
- HQVNEWCFYHHQES-UHFFFAOYSA-N silicon nitride Chemical compound N12[Si]34N5[Si]62N3[Si]51N64 HQVNEWCFYHHQES-UHFFFAOYSA-N 0.000 claims description 5
- 238000005530 etching Methods 0.000 claims description 4
- PCHJSUWPFVWCPO-UHFFFAOYSA-N gold Chemical compound [Au] PCHJSUWPFVWCPO-UHFFFAOYSA-N 0.000 claims description 4
- 229910052737 gold Inorganic materials 0.000 claims description 4
- 239000010931 gold Substances 0.000 claims description 4
- 239000000463 material Substances 0.000 claims description 4
- 150000002739 metals Chemical class 0.000 claims description 4
- 229910052782 aluminium Inorganic materials 0.000 claims description 3
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims description 3
- 239000011248 coating agent Substances 0.000 claims description 3
- 238000000576 coating method Methods 0.000 claims description 3
- 238000005459 micromachining Methods 0.000 claims description 3
- 238000005520 cutting process Methods 0.000 claims description 2
- 229920000557 Nafion® Polymers 0.000 claims 1
- 230000035945 sensitivity Effects 0.000 abstract description 9
- 238000009826 distribution Methods 0.000 abstract description 3
- 238000000429 assembly Methods 0.000 abstract description 2
- 230000000712 assembly Effects 0.000 abstract description 2
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 6
- 238000009423 ventilation Methods 0.000 description 6
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 4
- 238000005259 measurement Methods 0.000 description 4
- 230000002269 spontaneous effect Effects 0.000 description 4
- KWYUFKZDYYNOTN-UHFFFAOYSA-M Potassium hydroxide Chemical compound [OH-].[K+] KWYUFKZDYYNOTN-UHFFFAOYSA-M 0.000 description 3
- 230000009286 beneficial effect Effects 0.000 description 3
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- 238000001514 detection method Methods 0.000 description 2
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- 229910052759 nickel Inorganic materials 0.000 description 2
- 238000012545 processing Methods 0.000 description 2
- WGTYBPLFGIVFAS-UHFFFAOYSA-M tetramethylammonium hydroxide Chemical compound [OH-].C[N+](C)(C)C WGTYBPLFGIVFAS-UHFFFAOYSA-M 0.000 description 2
- 208000004756 Respiratory Insufficiency Diseases 0.000 description 1
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 1
- 230000004888 barrier function Effects 0.000 description 1
- 239000003153 chemical reaction reagent Substances 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 230000005611 electricity Effects 0.000 description 1
- 238000005566 electron beam evaporation Methods 0.000 description 1
- 238000005328 electron beam physical vapour deposition Methods 0.000 description 1
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Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
- G01D21/00—Measuring or testing not otherwise provided for
- G01D21/02—Measuring two or more variables by means not covered by a single other subclass
-
- 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]
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N25/00—Investigating or analyzing materials by the use of thermal means
- G01N25/18—Investigating or analyzing materials by the use of thermal means by investigating thermal conductivity
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N25/00—Investigating or analyzing materials by the use of thermal means
- G01N25/20—Investigating or analyzing materials by the use of thermal means by investigating the development of heat, i.e. calorimetry, e.g. by measuring specific heat, by measuring thermal conductivity
Abstract
The invention provides a MEMS respiration monitoring sensing chip and a preparation method thereof, wherein the flow of respiration airflow changes the temperature distribution of the chip surface, and four calorimetric elements positioned on the chip surface obtain the flow, speed and direction of the respiration airflow by measuring the change of a temperature field; the chip can be placed in a specific airflow channel, and the average temperature difference and the corresponding position determine the forward direction and the reverse direction of airflow; the calorimetric sensor is composed of a micromachined thermopile, so that passive monitoring can be realized; a thermal conductive element located in the center of the chip monitors the thermal conductivity change of the air flow to obtain the carbon dioxide content of the respiratory air flow. The chip has the advantages of small volume, passivity, high sensitivity and the like, is convenient to process and use, and can also form a portable sensor assembly together with other assemblies, thereby carrying out close-range real-time monitoring on respiratory conditions.
Description
Technical Field
The invention belongs to the technical field of respiratory sensors, and particularly relates to a MEMS respiratory monitoring sensing chip and a preparation method thereof.
Background
Noninvasive ventilation is a ventilation mode in which a mask or a nasal mask is worn to perform mechanical ventilation. The most critical issues of non-invasive ventilation are man-machine synchrony, i.e. synchrony of ventilator start delivery with spontaneous breathing inhalation, and synchrony of ventilator switch to exhalation phase with spontaneous breathing start exhalation. The existing method for processing the noninvasive ventilation synchronization is indirect, no matter what sensor is used and no matter where the sensor is placed is a mask or a proximal pipeline, the inhalation and exhalation of spontaneous breathing cannot be directly detected, so the method for processing the man-machine synchronization is realized through an indirect algorithm although various, so that the quality of the man-machine synchronization still has a great gap, and the comfort, tolerance, compliance and effectiveness of the noninvasive ventilation cannot be ensured. In addition, real-time respiration monitoring is also an important link, if spontaneous respiration can be continuously and dynamically monitored, the method is beneficial to evaluating the progress degree of respiratory failure before mechanical ventilation, so that the timing and the intensity of ventilation treatment are judged. The existing sensor has the defects of large volume, power supply matching, limited detection precision and the like, so that short-distance real-time and high-precision respiration monitoring cannot be realized, and the sensor is also an important problem faced by the person skilled in the art.
Disclosure of Invention
In order to solve the technical problems, the invention provides a MEMS respiration monitoring sensing chip, a preparation method and a sensor assembly.
The specific technical scheme of the invention is as follows:
the invention provides an MEMS respiration monitoring sensing chip, which comprises a substrate and a plurality of sensing elements arranged on the substrate, wherein the sensing elements comprise at least two calorimetric elements as respiration flow and flow direction sensing elements and at least one thermal conduction element as carbon dioxide sensing elements, the respiration flow and flow direction sensing elements are formed by thermopiles or thermocouples, and the carbon dioxide sensing elements are made of thermocouple metals; the respiratory flow and flow direction sensing elements are symmetrically distributed on the substrate, and the flow and direction of the respiratory airflow are obtained according to the change condition of the surface temperature field of the sensing chip under the respiratory airflow; one part of the carbon dioxide sensing element is covered with an inert coating, the other part of the carbon dioxide sensing element is exposed in the air, and the carbon dioxide content in the respiratory airflow is obtained according to the thermal conductivity change condition of the two parts; and the plurality of sensing elements respectively transmit the acquired signals to the receiving terminal through preset signal paths.
Further, the base body is square, the four respiratory flow and flow direction sensing units are respectively arranged at four corners of the base body, and the two carbon dioxide sensing units are respectively symmetrically arranged at two sides of the middle of the base body.
Further, an insulating layer, a chip layer and a passivation layer are sequentially arranged on the substrate from bottom to top, the plurality of sensing elements are arranged on the chip layer, and the chip layer and the passivation layer are mutually fused at the etching position.
Further, a plurality of heat insulation cavities are arranged at the positions of the bottom of the base body, which are opposite to the plurality of sensing elements.
Further, the chip layer is further provided with a plurality of groups of signal lines which are respectively conducted with the sensing elements.
Further, the respiratory flow and flow direction sensing element is composed of a thermopile or a thermocouple, and the thickness is 80-200 nm; the carbon dioxide sensing element is made of thermocouple metal, which may be doped with polysilicon.
Further, the signal line is made of gold or aluminum, in which conductive polysilicon may be doped; the thickness of the signal wire is 100-300 nm.
In another aspect, the invention provides a method for preparing the MEMS respiration monitoring sensing chip, which comprises the following steps:
depositing silicon nitride on the upper and lower surfaces of the substrate;
depositing the sensing element onto the upper surface of the substrate and connecting with a predetermined signal path;
performing surface passivation on all areas of the upper surface of the substrate, and constructing a passivation layer covering the upper surface of the substrate and the sensing element;
the lower surface of the matrix is provided with a plurality of empty slots corresponding to the sensing elements to form a heat insulation cavity;
and after finishing the micromachining process, cutting and separating to obtain the chip.
The invention also provides a respiration monitoring sensor component, which comprises the chip, a flexible circuit board, a flexible cable and a control module, wherein the chip is packaged on the flexible circuit board to form a monitoring part, and the monitoring part is connected with the control module through the flexible cable; the control module comprises a main control circuit, a power supply module, a wireless communication module and an antenna.
Further, the sensor assembly also includes a sampling tube in which the chip is packaged.
The beneficial effects of the invention are as follows: the invention provides a MEMS respiration monitoring sensing chip and a preparation method thereof, wherein the flow of respiration airflow changes the temperature distribution of the chip surface, and four calorimetric elements positioned on the chip surface obtain the flow, speed and direction of the respiration airflow by measuring the change of a temperature field; the chip can be placed in a specific airflow channel, and the average temperature difference and the corresponding position determine the forward direction and the reverse direction of airflow; the calorimetric sensor is composed of a micromachined thermopile, so that passive monitoring can be realized; a thermal conductive element located in the center of the chip monitors the thermal conductivity change of the air flow to obtain the carbon dioxide content of the respiratory air flow. The chip has the advantages of small volume, passivity, high sensitivity and the like, is convenient to process and use, and can also form a portable sensor assembly together with other assemblies, thereby carrying out close-range real-time monitoring on respiratory conditions.
Drawings
FIG. 1 is a schematic diagram of a MEMS respiration monitoring sensor chip according to embodiment 1;
FIG. 2 is a longitudinal cross-sectional view of the MEMS respiration monitoring sensor chip described in example 1;
FIG. 3 is a schematic view of a respiratory monitoring sensor assembly according to embodiment 3;
fig. 4 is a schematic diagram of the packaging mode of the respiration monitoring sensor assembly according to embodiment 3 in the use state.
Wherein: 100-chip; 101-substrate; 112. 114, 116, 118-respiratory flow and flow direction sensing element; 122. 124, 126, 128-insulating chambers; 131. 132, 134, 155, 156-signal connection lines; 150-a carbon dioxide sensing element; 200-monitoring a component; 210-a flexible circuit board; 300-flexible cable; 400-a control module; 410-a master circuit; 420-a wireless communication module; 422-antenna; 430-a power module; 510-square sampling tube; 520-circular sampling tube.
Detailed Description
The invention will be described in further detail with reference to the accompanying drawings and the following examples.
Example 1
As shown in fig. 1, an embodiment of the present invention provides a MEMS respiration monitoring sensing chip, which includes a substrate 101 and a plurality of sensing elements disposed on the substrate 101, wherein the sensing elements include at least two calorimetric elements as respiration flow and flow direction sensing elements and at least one thermal conduction element as carbon dioxide sensing element, the respiration flow and flow direction sensing elements are formed by a thermopile or a thermocouple, and the carbon dioxide sensing elements are made of metals with larger temperature coefficients (such as nickel, platinum, etc.); the respiratory flow and the flow direction sensing elements are symmetrically distributed on the substrate, and the flow and the direction of respiratory airflow are obtained according to the change condition of the surface temperature field of the sensing chip under respiratory flow; one part of the carbon dioxide sensing element is covered with an inert coating (passivation layer), the other part of the carbon dioxide sensing element is exposed in the air, and the carbon dioxide content in the respiratory airflow is obtained according to the thermal conductivity change condition of the two parts; the plurality of sensing elements respectively transmit the acquired signals to the receiving terminal through preset signal paths.
When the chip works, the respiratory airflow flows through the surface of the substrate 101, the temperature distribution of each position is changed, the calorimetric element formed by a thermopile or a thermocouple senses the temperature field change of the position, the flow direction of the airflow can be determined according to the difference between groups, the average value of the amplitude change between groups is related to the flow, and the actual measurement data can be obtained by calculating according to the reference value obtained by the reference standard flow device in advance. If the carbon dioxide in the air flow is required to be monitored, the heat conduction element is started, errors caused by the environment and other effects can be eliminated through the signal difference between the part covered with the passivation layer and the exposed part, so that the optimal sensitivity is achieved, the heat conduction of the air is directly related to the air component, and the carbon dioxide concentration value of the current air flow can be obtained by calibrating according to the reference air in advance.
In practice, the calorimetric element is fabricated from a thermocouple metal, preferably nickel or platinum, which may be doped with polysilicon. Platinum is a stable metal with excellent temperature coefficient to provide the required sensitivity, while doped polysilicon can be fabricated using standard compatible metal oxide semiconductor processes, which in combination with thermocouple metals can ensure the stability and reliability of the chip output.
The heat conduction element is made of a thermopile or a thermocouple, and in the non-power supply state, the calorimetric element can sense the temperature change of the breathing air flow, so that a corresponding temperature control signal is transmitted to an external receiving terminal, and the breathing condition is monitored. The form can realize automatic annular shape in the shake year, can effectively save electricity and energy, and does not need an external power supply. When the heat conducting element works, micro-power consumption current passes through the heat conducting element, so that a micro-heater is formed, and a reference temperature, namely a thermal field, can be provided for the heat conducting element at the same time, so that the sensitivity of the heat conducting element is further improved. The arrangement can reduce the number of parts, thereby reducing the size of the chip and being beneficial to miniaturization improvement of the chip.
In a preferred embodiment, the base 101 is square, the four respiratory flow and flow direction sensing elements (112, 114, 116, 118) are all arranged at four corners of the base, the two carbon dioxide sensing units 150 are all arranged in the middle of the base 101 and symmetrically arranged at two sides, that is, one respiratory flow and flow direction sensing element is arranged at the upstream and downstream positions of each carbon dioxide sensing unit 150. Through the design, the chip can sense the air flow in opposite directions, so that the flow velocity measurement requirements in different directions are met.
As shown in fig. 2, in some specific embodiments, the substrate 1 may be manufactured to have a structure including, from bottom to top, an insulating layer 160, a chip layer 180, and a passivation layer 170, where the sensing element is disposed on the chip layer 180, and the passivation layer 170 is fused with the chip layer 180 at the etching site; the insulating layer 160 acts as a thermal barrier and provides the necessary mechanical strength to weaken or even eliminate the pressure applied to the chip surface during measurement, thereby effectively reducing the damage to the chip during use.
In practice, the compressive strength of the insulating layer 160 may be adjusted by varying the thickness of the insulating layer during the manufacturing process. Specifically, the insulating layer 160 may be made of silicon nitride, etc., and its center is deformed d= (α×p×b) 4 )/(E*t 3 ) Wherein α is a constant value under the condition of applying uniform pressure p theretoB is the side length of the insulating layer, t is the thickness of the insulating layer, and E is the Young's modulus of the material (silicon oxide, etc.). Thus, the accuracy requirements in the application can be calculated from the d/b bias, and the thickness of the insulating layer 160 can be determined for the preferred chip.
In some specific embodiments, a plurality of heat insulation cavities, preferably 5, are further disposed at the bottom of the base 1 opposite to the sensing elements, wherein 122, 124, 126, 128 respectively correspond to the respiratory flow and flow sensing units 112, 114, 116, 118, 125 are disposed at the bottom center of the base 1, and two ends respectively correspond to two carbon dioxide sensing units 150.
In actual manufacturing, an ion deep etching method or a wet etching method (by means of chemical reagents such as potassium hydroxide or tetramethylammonium hydroxide) can be adopted to dig grooves in the bottom of the substrate 1, a heat insulation cavity is manufactured, and thermal isolation can be established between the sensing elements and the respiratory airflow, so that the working sensitivity of the sensing elements is ensured.
In some specific embodiments, the chip layer 180 is further provided with a plurality of signal lines, preferably 6 sets, respectively connected to the plurality of sensing elements, wherein 131, 132, 133, 134 are respectively connected to the respiratory flow and flow sensing units 112, 114, 116, 118, and 155, 156 are respectively connected to the two carbon dioxide sensing units 150.
In practical manufacturing, the signal line is made of gold or aluminum by electron beam evaporation or physical vapor deposition, etc., and the metal can be doped with conductive polysilicon, and the most preferable material is gold. The thickness of the signal line is preferably in the range of 100 to 300nm, and in this range, the stability of the optimized material and the sensitivity of the chip are optimized, wherein 200nm is the most preferable.
Example 2
The embodiment 2 provides a method for preparing the MEMS respiration monitoring sensing chip in the embodiment 1, which specifically comprises the following steps:
silicon nitride is deposited on the upper surface and the lower surface of the matrix, and passivation treatment is carried out on the surface of the chip so as to improve the corrosion resistance of the chip;
depositing a sensing element on the upper surface of the substrate and connecting the sensing element with a predetermined signal path, thereby realizing signal transmission between the sensing element and a corresponding control module;
performing surface passivation on all areas of the upper surface of the substrate, and constructing a passivation layer covering the upper surface of the substrate and the sensing element;
the lower surface of the matrix is provided with a plurality of empty slots corresponding to the sensing elements to form a heat insulation cavity;
after the micromachining process is completed, dicing and separation are performed, thereby obtaining a chip.
In the process, silicon nitride is deposited on the surface of the matrix, and passivation treatment is performed on the surface of the matrix again after the sensing element and the signal path are distributed, so that the corrosion resistance of the chip can be further improved through two rounds of passivation treatment; the heat insulation cavity is arranged to provide heat insulation between the heat measuring element and the respiratory airflow medium, so that the sensitivity of the heat measuring element can be ensured.
The MEMS respiration monitoring sensing chip obtained by the method can realize the respiration monitoring function without an active device, has excellent corrosion resistance and measurement sensitivity, effectively reduces the size of the chip, and improves the flexibility and portability of the chip in use.
Example 3
As shown in fig. 3, embodiment 3 provides a respiration monitoring sensor assembly, which includes the chip 100 in embodiment 1, and further includes a flexible circuit board 210, a flexible cable 300, and a control module 400, wherein the chip 100 is packaged on the flexible circuit board 210 to form a monitoring component 200, and the monitoring component 200 is connected with the control module 400 through the flexible cable 210; the control module 400 specifically includes a main control circuit 410, a power module 430, a wireless communication module 420 (preferably a bluetooth module), and an antenna 422, but is not limited to the above.
As shown in fig. 4, in actual use, the above components can be packaged in a sampling tube 510 (square) or 520 (round) and attached to the upper lip or the respiratory mask of a patient needing respiratory monitoring, so that the air inlet of the sampling tube is aligned to the nasal cavity, thereby collecting and monitoring the respiratory condition of the patient in a close-range real-time manner and effectively improving the detection precision.
The foregoing examples illustrate only a few embodiments of the invention and are described in detail herein without thereby limiting the scope of the invention. It should be noted that it will be apparent to those skilled in the art that several variations and modifications can be made without departing from the spirit of the invention, which are all within the scope of the invention. Accordingly, the scope of protection of the present invention is to be determined by the appended claims.
Claims (10)
1. The MEMS respiration monitoring sensing chip is characterized by comprising a substrate and a plurality of sensing elements arranged on the substrate, wherein the sensing elements comprise at least two calorimetric elements serving as respiration flow and flow direction sensing elements and at least one thermal conduction element serving as carbon dioxide sensing elements, the respiration flow and flow direction sensing elements are formed by thermopiles or thermocouples, and the carbon dioxide sensing elements are made of thermocouple metals; the respiratory flow and flow direction sensing elements are symmetrically distributed on the substrate, and the flow and direction of the respiratory airflow are obtained according to the change condition of the surface temperature field of the sensing chip under the respiratory airflow; one part of the carbon dioxide sensing element is covered with an inert coating, the other part of the carbon dioxide sensing element is exposed in the air, and the carbon dioxide content in the respiratory airflow is obtained according to the thermal conductivity change condition of the two parts; and the plurality of sensing elements respectively transmit the acquired signals to the receiving terminal through preset signal paths.
2. The MEMS respiration monitoring sensor chip of claim 1, wherein the substrate is square, the respiration flow and flow direction sensing units are four in number and are respectively arranged at four corners of the substrate, and the carbon dioxide sensing elements are two in number and are respectively symmetrically arranged at two sides of the middle of the substrate.
3. The MEMS respiration monitoring sensor chip of claim 1, wherein the substrate is provided with an insulating layer, a chip layer and a passivation layer in sequence from bottom to top, the plurality of sensor elements are arranged on the chip layer, and the chip layer and the passivation layer are mutually fused at the etching position.
4. The MEMS respiratory monitoring sensor chip of claim 3, wherein the base bottom is provided with a plurality of insulating cavities at positions opposite the plurality of sensing elements.
5. The MEMS respiratory monitoring sensor chip of claim 3, wherein the chip layer is further provided with a plurality of sets of signal lines that are respectively in conductive communication with a plurality of the sensing elements.
6. The MEMS respiratory monitoring sensor chip of claim 1, wherein the respiratory flow and flow sensing element has a thickness of 80-200 nm; polysilicon is doped in the thermocouple metal that constitutes the carbon dioxide sensing element.
7. The MEMS respiratory monitoring sensor chip of claim 5, wherein the signal line is made of gold or aluminum, wherein conductive polysilicon is doped; the thickness of the signal line is 100-300 nm.
8. A method for preparing the MEMS respiration monitoring sensor chip as claimed in any one of claims 1 to 7, comprising the steps of:
depositing silicon nitride on the upper and lower surfaces of the substrate;
depositing the sensing element onto the upper surface of the substrate and connecting with a predetermined signal path;
performing surface passivation on all areas of the upper surface of the substrate, and constructing a passivation layer covering the upper surface of the substrate and the sensing element;
the lower surface of the matrix is provided with a plurality of empty slots corresponding to the sensing elements to form a heat insulation cavity;
and after finishing the micromachining process, cutting and separating to obtain the chip.
9. A respiration monitoring sensor assembly comprising the chip of any one of claims 1 to 7, further comprising a flexible circuit board, a flexible cable and a control module, wherein the chip is packaged on the flexible circuit board to form a monitoring component, and the monitoring component is connected with the control module through the flexible cable; the control module comprises a main control circuit, a power supply module, a wireless communication module and an antenna.
10. The respiration monitoring sensor assembly of claim 9, further comprising a sampling tube of Nafion material, the chip being packaged in the sampling tube.
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