Preparation method of MEMS hydrogen sensor

Abstract

The invention discloses a preparation method of an MEMS hydrogen sensor. The MEMS hydrogen sensor comprises a bottom plate, an MEMS base layer and a hydrogen sensitive material, the hydrogen sensitive material is arranged above the MEMS base layer and comprises three metal oxide nano sensitive film layers and a noble metal deposition layer, and a tin dioxide sensitive film layer, a tin dioxide and zinc oxide composite sensitive film layer and a nickel oxide sensitive film layer are sequentially arranged on the surface of the MEMS base layer to form a three-layer metal oxide nano sensitive film layer semiconductor; the specific beneficial effects are as follows: zinc oxide and stannic oxide have good response to hydrogen; hydrogen sensors with various shapes, specifications and thicknesses can be prepared by an ink-jet printing method; hydrogen sensors with various properties are prepared by adjusting the mass fraction ratio of zinc oxide, stannic oxide and nickel oxide; the sensor has the advantages of high sensitivity, low detection limit, fast response, small size, low power consumption, low cost, large-scale industrial production and the like, and can be applied to monitoring of various environments.

Description

Technical Field

[0001] The invention relates to the technical field of odor detection, and in particular to a method for preparing a MEMS hydrogen sensor. Background Art

[0002] In recent years, with the acceleration of industrialization and urbanization, hydrogen has been widely used in industry, energy and scientific research. It is a candidate for clean energy and can be used in fuel cells as well as hydrogen energy storage and transmission. In addition, hydrogen is also used in many fields such as chemical synthesis, electronics industry and metal production. Although hydrogen has many favorable properties, it is also a highly flammable gas. In hydrogen-related applications, safety has always been a concern that must be paid great attention to. Leaked hydrogen may cause explosions or fires, so reliable hydrogen detection and monitoring systems are required. In applications such as hydrogen fuel cell vehicles, hydrogen storage and hydrogen production, timely monitoring of hydrogen leaks is crucial. Hydrogen sensors can help monitor hydrogen concentrations so that appropriate measures can be taken at the early stage of leakage to avoid accidents that cause human or economic losses.

[0003] At present, hydrogen monitoring technologies mainly include several types: electrochemical sensors, metal oxide semiconductor (MOS) sensors, optical sensors and acoustic sensors. Each technology has its own unique advantages and disadvantages: electrochemical sensors detect hydrogen through electrochemical reactions. They usually have high sensitivity and good selectivity, but may be affected by temperature and humidity and need to be calibrated regularly; metal oxide semiconductor (MOS) sensors detect hydrogen through the reaction of hydrogen with metal oxides on the surface of the sensor. This type of sensor is sensitive to temperature changes and is greatly affected by ambient temperature, thus affecting the accuracy of monitoring; optical sensors use spectral technology to detect hydrogen, are not easily affected by chemical interference, and can provide non-contact remote detection, but require complex and expensive instruments and equipment, and are costly; acoustic sensors monitor hydrogen by measuring the interaction between gas and sound waves. They are relatively simple and low-cost, but not as sensitive as other types of sensors, have slow monitoring responses, and are not safe enough.

[0004] The above-mentioned current hydrogen sensors still have some problems in terms of sensitivity, accuracy, stability, response speed and economic cost. Therefore, the development of high-performance hydrogen sensors has important research significance and application value to meet the needs of industrial preparation, industrial application and urbanization process. Summary of the invention

[0005] The purpose of the present invention is to provide a method for preparing a MEMS hydrogen sensor. By utilizing MEMS nanofabrication technology, a hydrogen sensor with small weight, high sensitivity, strong accuracy, excellent stability, fast response speed and low economic cost can be prepared, thereby realizing accurate monitoring of hydrogen to solve the objective problems existing in the above-mentioned background technology.

[0006] To achieve the above-mentioned object, the present invention provides the following technical solutions: a method for preparing a MEMS hydrogen sensor, including a hydrogen sensor and a method for preparing the same; The hydrogen sensor comprises a base plate, a MEMS substrate, and a hydrogen sensitive material; The bottom plate is configured as a "U"-shaped PCB board with a hollow hole in the middle, four circuit terminals are respectively arranged at the four corners of one side of the bottom plate, and four screw holes are fixedly arranged at the centers of the four circuit terminals; a four-legged bracket is fixedly arranged on one side of the hollow hole in the middle of the bottom plate, and the four legs of the four-legged bracket are respectively connected to the four circuit terminals, and a pair of interdigital electrode circuits are fixedly arranged on two legs on a diagonal line and the corresponding two circuit connection terminals; The MEMS substrate is located in the middle of one side of the four-legged support and is configured as a micro-heated interdigital electrode composite silicon wafer. A pair of interdigital electrode circuits on the four-legged support are connected to the interdigital electrode composite silicon wafer for power supply. The hydrogen sensitive material is arranged on the MEMS base layer, and includes three layers of metal oxide nano-sensitive film layers and a noble metal deposition layer; The three-layer metal oxide nano-sensitive film layer is sequentially arranged on the surface of the MEMS base layer as a tin dioxide sensitive film layer, a tin dioxide and zinc oxide composite sensitive film layer, and a nickel oxide sensitive film layer to form the three-layer metal oxide nano-sensitive film layer semiconductor, and the total thickness is set to 50 to 500 nanometers;

[0007] The noble metal deposition layer is a palladium metal layer, which is deposited on the surface of the nickel oxide sensitive film layer.

[0008] The preparation method of the hydrogen sensor comprises: The preparation method of the tin dioxide sensitive film layer, the preparation method of the tin dioxide and zinc oxide composite sensitive film layer, the preparation method of the nickel oxide sensitive film layer, and the preparation method of the precious metal deposition layer; The preparation method of the tin dioxide sensitive film layer: Tin tetrachloride is the source of tin dioxide, ethanolamine is the reducing agent, and ethanol and deionized water are the solvents; the concentration of tin tetrachloride is 0.01-10M, the concentration of ethanolamine is 0.01-10M, the molar ratio of tin tetrachloride to ethanolamine is 1:1, and the mass ratio of ethanol to deionized water is 1:1; Further, 50 ml of ethanol and 50 ml of deionized water were added to the container in proportion, and then 0.075-7.5 ml of ethanolamine was added, and the mixture was stirred thoroughly. Then 0.075-7.5 ml of tin tetrachloride was added, and the mixture was stirred thoroughly. The mixture was heated to 30° C. to 90° C. and stirred with a magnetic stirrer until a transparent and slightly yellow solution was obtained, thereby obtaining the tin dioxide ink solution. Further, the tin dioxide ink is attached to the MEMS substrate by inkjet printing; Further, the bottom plate with the tin dioxide ink attached thereto is placed in a sintering furnace, and sintered at a high temperature of 200 to 500° C. to form the tin dioxide sensitive film layer, with a thickness of 10 to 200 nanometers; The preparation method of the composite sensitive film layer of tin dioxide and zinc oxide: Tin tetrachloride is the source of tin dioxide, zinc acetate dihydrate is the source of zinc oxide, ethanolamine is the reducing agent, and ethanol and deionized water are the solvents; wherein the concentration of tin tetrachloride is 0.01-10M, the concentration of zinc acetate dihydrate is 0.01-10M, the concentration of ethanolamine is 0.01-10M, the molar ratio of tin tetrachloride to zinc acetate dihydrate is 1-10:1, the molar ratio of tin tetrachloride and zinc acetate dihydrate to ethanolamine is 1:1, and the mass ratio of ethanol to deionized water is 1:1; Further, 50 ml of ethanol and 50 ml of deionized water are added to the container in proportion, followed by 0.1 to 10 ml of ethanolamine, and the mixture is stirred thoroughly. Then, 0.05 to 5 ml of tin tetrachloride and 0.05 to 5 ml of zinc acetate dihydrate are added, stirred thoroughly, heated to 30° C. to 90° C., and stirred magnetically until a transparent slightly yellow solution is obtained, thereby obtaining the tin dioxide and zinc oxide composite ink solution, wherein the ratio of tin dioxide to zinc oxide is 1 to 10:1; Furthermore, the tin dioxide and zinc oxide composite ink is attached to the sintered and fixed tin dioxide sensitive film layer by inkjet printing; Further, the bottom plate with the tin dioxide and zinc oxide composite ink attached thereto is placed in a sintering furnace, and sintered at a high temperature of 300 to 500° C. to form the tin dioxide and zinc oxide composite sensitive film layer, with a thickness of 10 to 100 nanometers; The preparation method of the nickel oxide sensitive film layer: Nickel chloride hexahydrate is the source of nickel oxide, ethanolamine is the reducing agent, and ethanol and deionized water are the solvents; wherein the concentration of nickel chloride hexahydrate is 0.01-10M, the concentration of ethanolamine is 0.01-10M, the molar ratio of ethanolamine to nickel chloride hexahydrate is 1:1, and the mass ratio of ethanol to deionized water is 1:1; Further, 50 ml of ethanol and 50 ml of deionized water are added to the container in proportion, and then 0.05-5 ml of ethanolamine is added, and the mixture is stirred thoroughly. Then 0.05-5 ml of nickel chloride hexahydrate is added, and the mixture is stirred thoroughly. The mixture is heated to 30° C. to 90° C. and stirred with a magnetic force until a transparent green solution is obtained, thereby obtaining the nickel oxide ink solution. Furthermore, the nickel oxide ink is attached to the sintered and fixed tin dioxide and zinc oxide composite sensitive film layer by inkjet printing; Furthermore, the bottom plate with the nickel oxide ink attached thereto is placed in a sintering furnace, and sintered at a high temperature of 300 to 500° C. to form the nickel oxide sensitive film layer, with a thickness of 1 to 100 nanometers; A method for preparing the noble metal deposit layer; Palladium chloride is the source of palladium, ethanol and deionized water are solvents, and the concentration of palladium chloride is 0.001-0.1M; Further, 50 ml of ethanol and 50 ml of deionized water were added to the container in proportion, and then 0.005-0.5 ml of palladium chloride was added and stirred thoroughly to prepare a palladium ink solution; Furthermore, the palladium ink is attached to the sintered and fixed nickel oxide sensitive film layer by inkjet printing. Further, the base plate with the palladium ink attached thereto is placed in a sintering furnace, and sintered at a high temperature of 300 to 500° C. to form the palladium metal layer, with a thickness of 0.1 to 100 nanometers; Finally, an ultrasonic bonding machine is used to bond the gold wires to form the hydrogen sensor. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 It is a schematic diagram of the overall structure of the hydrogen sensor of the present invention; Figure 2 It is a schematic diagram of the longitudinal cross-section structure of the MEMS substrate and the hydrogen sensitive material of the present invention; Figure 3 The response curves of the hydrogen sensor of the present invention exposed to different concentrations of hydrogen atmosphere at room temperature; Figure 4 This is a comparison diagram of the responses of the hydrogen sensor of the present invention when exposed to different gas atmospheres with different concentrations at room temperature; Figure 5 This is a schematic diagram of the long-term stability of the hydrogen sensor of the present invention; Figure 6 is a repetitive schematic diagram of the hydrogen sensor of the present invention; Figure 7 This is a silicon poisoning resistance test response diagram of the hydrogen sensor of the present invention. DETAILED DESCRIPTION

[0010] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0011] In this specific embodiment, Figure 1 , Figure 2 As shown, a method for preparing a MEMS hydrogen sensor includes a hydrogen sensor and a method for preparing the same; The hydrogen sensor comprises a base plate 1, a MEMS substrate 40, and a hydrogen sensitive material 4; The bottom plate 1 is configured as a U-shaped PCB board with a hollow hole 3 in the middle, and four circuit terminals 2 are respectively arranged at the four corners of one side of the bottom plate 1, and four screw holes are fixedly arranged at the centers of the four circuit terminals 2; a four-legged bracket 5 is fixedly arranged on one side of the hollow hole 3 in the middle of the bottom plate 1, and the four legs of the four-legged bracket 5 are respectively connected to the four circuit terminals 2, and a pair of interdigital electrode circuits 6 are fixedly arranged on two legs on a diagonal line and the corresponding two circuit connection terminals 2; The MEMS substrate 40 is located in the middle of one side of the four-legged support 5 and is configured as a micro-heated interdigital electrode composite silicon wafer. A pair of interdigital electrode circuits 6 on the four-legged support 5 are connected to the interdigital electrode composite silicon wafer for power supply. The hydrogen sensitive material 4 is disposed above the MEMS substrate 40 and includes three layers of metal oxide nano-sensitive film layers and a noble metal deposition layer 44; The three-layer metal oxide nano-sensitive film layer is sequentially arranged on the surface of the MEMS substrate 40 as a tin dioxide sensitive film layer 41, a tin dioxide and zinc oxide composite sensitive film layer 42, and a nickel oxide sensitive film layer 43, forming the three-layer metal oxide nano-sensitive film layer semiconductor, and the total thickness is set to 50-500 nanometers; The noble metal deposition layer 44 is a palladium metal layer, which is deposited on the surface of the nickel oxide sensitive film layer 43 .

[0012] In this specific embodiment, Figure 1 , Figure 2 As shown, the preparation method of the hydrogen sensor includes: The preparation method of the tin dioxide sensitive film layer 41, the preparation method of the tin dioxide and zinc oxide composite sensitive film layer 42, the preparation method of the nickel oxide sensitive film layer 43, and the preparation method of the noble metal deposition layer 44; Example 1 of the method for preparing the tin dioxide sensitive film layer 41: Tin tetrachloride is the source of tin dioxide, ethanolamine is the reducing agent, and ethanol and deionized water are the solvents; the concentration of tin tetrachloride is 0.01-10M, the concentration of ethanolamine is 0.01-10M, the molar ratio of tin tetrachloride to ethanolamine is 1:1, and the mass ratio of ethanol to deionized water is 1:1; Further, 50 ml of ethanol and 50 ml of deionized water were added to the container in proportion, and then 0.075-7.5 ml of ethanolamine was added, and the mixture was stirred thoroughly. Then 0.075-7.5 ml of tin tetrachloride was added, and the mixture was stirred thoroughly. The mixture was heated to 30° C. to 90° C. and stirred with a magnetic stirrer until a transparent and slightly yellow solution was obtained, thereby obtaining the tin dioxide ink solution. Further, the tin dioxide ink is attached to the MEMS substrate 40 by inkjet printing; Furthermore, the bottom plate 1 with the tin dioxide ink attached thereto is placed in a sintering furnace and sintered at a high temperature of 200 to 500° C. to form the tin dioxide sensitive film layer 41 with a thickness of 10 to 200 nanometers. If the tin dioxide sensitive film layer 41 is too thin, the resistance is too large, and the stability of hydrogen monitoring is low; if the tin dioxide sensitive film layer 41 is too thick, the resistance is too small, and the responsiveness of hydrogen monitoring is low; Example 1 of the method for preparing the tin dioxide and zinc oxide composite sensitive film layer 42: Tin tetrachloride is the source of tin dioxide, zinc acetate dihydrate is the source of zinc oxide, ethanolamine is the reducing agent, and ethanol and deionized water are the solvents; wherein the concentration of tin tetrachloride is 0.01-10M, the concentration of zinc acetate dihydrate is 0.01-10M, the concentration of ethanolamine is 0.01-10M, the molar ratio of tin tetrachloride to zinc acetate dihydrate is 1-10:1, the molar ratio of tin tetrachloride and zinc acetate dihydrate to ethanolamine is 1:1, and the mass ratio of ethanol to deionized water is 1:1; Further, 50 ml of ethanol and 50 ml of deionized water are added to the container in proportion, followed by 0.1 to 10 ml of ethanolamine, and the mixture is stirred thoroughly. Then, 0.05 to 5 ml of tin tetrachloride and 0.05 to 5 ml of zinc acetate dihydrate are added, and the mixture is stirred thoroughly. The mixture is heated to 30° C. to 90° C. and stirred by magnetic stirring until a transparent slightly yellow solution is obtained, thereby obtaining the tin dioxide and zinc oxide composite ink solution, wherein the ratio of tin dioxide to zinc oxide is 1 to 10:1. Furthermore, the tin dioxide and zinc oxide composite ink is attached to the sintered and fixed tin dioxide sensitive film layer 41 by inkjet printing; Furthermore, the bottom plate 1 with the tin dioxide and zinc oxide composite ink attached thereto is placed in a sintering furnace and sintered at a high temperature of 300-500° C. to form the tin dioxide and zinc oxide composite sensitive film layer 42 with a thickness of 10-100 nanometers. Based on the band gap width of zinc oxide being 3.37 eV and the band gap width of tin dioxide being 3.6 eV, the use of the two in combination can construct a nn heterojunction, increase the depletion layer thickness of the material, and further improve the hydrogen gas sensing performance of the material; at the same time, since the stability and hydrogen gas sensing performance of zinc oxide itself are relatively low, the zinc oxide doping ratio should not be too high and should be controlled within the range of 1% to 40%; Embodiment 1 of the method for preparing the nickel oxide sensitive film layer 43: Nickel chloride hexahydrate is the source of nickel oxide, ethanolamine is the reducing agent, and ethanol and deionized water are the solvents; wherein the concentration of nickel chloride hexahydrate is 0.01-10M, the concentration of ethanolamine is 0.01-10M, the molar ratio of ethanolamine to nickel chloride hexahydrate is 1:1, and the mass ratio of ethanol to deionized water is 1:1; Further, 50 ml of ethanol and 50 ml of deionized water are added to the container in proportion, and then 0.05-5 ml of ethanolamine is added, and the mixture is stirred thoroughly. Then 0.05-5 ml of nickel chloride hexahydrate is added, and the mixture is stirred thoroughly. The mixture is heated to 30° C. to 90° C. and stirred with a magnetic force until a transparent green solution is obtained, thereby obtaining the nickel oxide ink solution. Furthermore, the nickel oxide ink is attached to the sintered and fixed tin dioxide and zinc oxide composite sensitive film layer 42 by inkjet printing; Furthermore, the bottom plate 1 with the nickel oxide ink attached thereto is placed in a sintering furnace and sintered at a high temperature of 300-500° C. to form the nickel oxide sensitive film layer 43 with a thickness of 1-100 nanometers. The nickel oxide is a P-type semiconductor, and can form an NP heterojunction with the tin dioxide and zinc oxide composite sensitive film layer, greatly increasing the width of the depletion layer and the initial resistance of the material, thereby improving the hydrogen gas sensing performance of the sensitive material. However, the gas sensing performance of the nickel oxide material itself is relatively low, so it is not easy to be too thick; Embodiment 1 of the method for preparing the noble metal deposition layer 44; Palladium chloride is the source of palladium, ethanol and deionized water are solvents, and the concentration of palladium chloride is 0.001-0.1M; Further, 50 ml of ethanol and 50 ml of deionized water were added to the container in proportion, and then 0.005-0.5 ml of palladium chloride was added and stirred thoroughly to prepare a palladium ink solution; Furthermore, the palladium ink is attached to the sintered and fixed nickel oxide sensitive film layer 43 by inkjet printing. Further, the base plate with the palladium ink attached thereto is placed in a sintering furnace, and sintered at a high temperature of 300 to 500° C. to form the palladium metal layer, with a thickness of 0.1 to 100 nanometers; Palladium metal has a good catalytic decomposition effect on hydrogen, which can effectively improve hydrogen selectivity and responsiveness; if the palladium metal layer is too thin, the catalytic effect is small; if the palladium metal layer is too thick, the material directly conducts electricity based on the conductivity of the palladium metal itself, and the hydrogen gas sensitivity performance is reduced; Finally, an ultrasonic bonding machine is used to bond the gold wires to form the hydrogen sensor.

[0013] In this specific embodiment, Figure 1 , Figure 2 As shown, the preparation method of the tin dioxide sensitive film layer 41 is as follows: Add 50 ml of ethanol and 50 ml of deionized water to the container in proportion, then add 0.15-4 ml of ethanolamine, stir thoroughly, then add 0.15-4 ml of tin tetrachloride, stir thoroughly, heat to 30° C.-90° C., and stir magnetically until a transparent slightly yellow solution is obtained, thereby preparing the tin dioxide ink solution; Example 2 of the preparation method of the tin dioxide and zinc oxide composite sensitive film layer 42: Add 50 ml of ethanol and 50 ml of deionized water to the container in proportion, then add 0.2-5 ml of ethanolamine, stir thoroughly, then add 0.1-3 ml of tin tetrachloride and 0.1-3 ml of zinc acetate dihydrate, stir thoroughly, heat to 30° C.-90° C., and stir magnetically until a transparent slightly yellow solution is obtained to obtain the tin dioxide and zinc oxide composite ink solution, wherein the ratio of tin dioxide to zinc oxide is 1-10:1; Embodiment 2 of the method for preparing the nickel oxide sensitive film layer 43: Add 50 ml of ethanol and 50 ml of deionized water to the container in proportion, then add 0.1-3 ml of ethanolamine, stir thoroughly, then add 0.1-3 ml of nickel chloride hexahydrate, stir thoroughly, heat to 30° C.-90° C., and stir magnetically until a transparent green solution is obtained, thereby preparing the nickel oxide ink solution; Embodiment 2 of the method for preparing the noble metal deposition layer 44; Add 50 ml of ethanol and 50 ml of deionized water into a container in proportion, then add 0.01-0.3 ml of palladium chloride, and stir thoroughly to prepare a palladium ink solution.

[0014] In this specific embodiment, Figure 1 , Figure 2 As shown, the preparation method of the tin dioxide sensitive film layer 41 is as follows: Add 50 ml of ethanol and 50 ml of deionized water into the container in proportion, then add 0.3-2.5 ml of ethanolamine, stir thoroughly, then add 0.3-2.5 ml of tin tetrachloride, stir thoroughly, heat to 60° C., and stir magnetically until a transparent slightly yellow solution is obtained, thereby obtaining the tin dioxide ink solution; Embodiment 3 of the method for preparing the tin dioxide and zinc oxide composite sensitive film layer 42: Add 50 ml of ethanol and 50 ml of deionized water to the container in proportion, then add 4 to 6 ml of ethanolamine, stir thoroughly, then add 0.2 to 1.5 ml of tin tetrachloride and 0.1 to 0.5 ml of zinc acetate dihydrate, stir thoroughly, heat to 60° C., and stir magnetically until a transparent slightly yellow solution is obtained to obtain the tin dioxide and zinc oxide composite ink solution, wherein the ratio of tin dioxide to zinc oxide is 1 to 10:1; Embodiment 3 of the method for preparing the nickel oxide sensitive film layer 43: Add 50 ml of ethanol and 50 ml of deionized water into the container in proportion, then add 0.2-1 ml of ethanolamine, stir thoroughly, then add 0.2-1 ml of nickel chloride hexahydrate, stir thoroughly, heat to 60° C., and stir magnetically until a transparent green solution is obtained, thereby preparing the nickel oxide ink solution; Embodiment 3 of the method for preparing the noble metal deposition layer 44; 50 ml of ethanol and 50 ml of deionized water were added to the container in proportion, and then 0.05 ml of palladium chloride was added and stirred thoroughly to prepare a palladium ink solution.

[0015] In this specific embodiment, Figure 3 As shown, it is a response curve diagram of the hydrogen sensor printed in Example 1 of the present invention exposed to different concentrations of hydrogen atmosphere at room temperature; the test concentration is 10 ppm-3000 ppm, the higher the hydrogen concentration, the smaller the sensor resistance, the resistance value of the sensor in the air is 20 kΩ, the resistance value in 3000 ppm hydrogen is 0.5 kΩ, and the response value is 40.

[0016] In this specific embodiment, Figure 4 The figure shows the response comparison of the hydrogen sensor printed in the first embodiment of the present invention exposed to different gas atmospheres of different concentrations at room temperature. The sensor was mainly tested for five gases, hydrogen, ammonia, ethanol, carbon monoxide, and methane at 0-3000 ppm. The sensor showed good selectivity for hydrogen. H2 / S CO ≥10, S H2 / S 乙醇 ≥50.

[0017] In this specific embodiment, Figure 5 FIG. 4 is a schematic diagram of the long-term stability of the hydrogen sensor in Example 1 of the present invention; the sensor maintained 90% of its response to 100 ppm hydrogen for 6 months, and has good long-term stability.

[0018] In this specific embodiment, Figure 6 , which is a schematic diagram of the repeatability of the hydrogen sensor in the first embodiment of the present invention; the sensor's five-time repeatability response error to 100 ppm hydrogen is less than 5%.

[0019] In this specific embodiment, Figure 7 As shown, it is the silicon poisoning resistance test response diagram of the hydrogen sensor in Example 1 of the present invention; the sensor was tested for 40 hours of silicon poisoning resistance verification of 20 ppm hexamethyldisiloxane, and the error of the response value before and after the sensor was less than 20%, which has good silicon poisoning resistance characteristics.

[0020] According to the above-mentioned physical experimental test results, the formaldehyde sensor prepared by the preparation method of the present invention is superior to the existing hydrogen sensors on the market in terms of sensitivity, detection limit, response time, stability and sustainability.

[0021] Compared with the prior art, the advantages of the present invention are: The present invention discloses a method for preparing a MEMS hydrogen sensor, and the specific beneficial effects are as follows: a semiconductor metal oxide nanofilm hydrogen sensor with a plurality of NNP heterogeneous combinations and a preparation method thereof are provided; the power consumption of the sensor can be effectively reduced to 10 mW by inkjet printing and depositing three layers of nano-scale sensitive film layers on a MEMS substrate, while improving the stability and consistency of the material; a NNP heterojunction is constructed by depositing different types of semiconductor metal oxides, and a high-performance hydrogen sensor is realized by combining with precious metal catalysis, and the minimum detection limit of hydrogen reaches 100 ppb, with good selectivity (S H2 / S CO ≥10, S H2 / S 乙醇 ≥50), good long-term stability (half-year stability ≤2%) and good silicon resistance (100ppm hexamethyldisiloxane 40-hour stability ≤15%). The problems of traditional semiconductor oxide hydrogen sensors in high operating temperature and limited hydrogen selectivity have been improved. By developing a semiconductor metal oxide thin film sensor, we have achieved high sensitivity, fast response and low-concentration detection capabilities while significantly reducing costs. Thanks to its simple structure, excellent hydrogen-sensitive performance and compatibility with microelectronic processes, the hydrogen sensor is easy to integrate and is suitable for intelligent applications in advanced microelectromechanical systems and multifunctional sensors.

[0022] The core components used in the present invention are all high-precision standard devices (MEMS substrate) in the industry. Special-shaped parts can be customized according to the instructions and the drawings. The specific connection methods of each part adopt mature conventional means such as bolts, rivets, welding, etc. in the prior art. Machinery, parts and equipment all adopt conventional models in the prior art, and circuit connection, data transmission, etc. all adopt conventional connection methods in the prior art. They will not be described in detail here. The contents not described in detail in this specification belong to the prior art known to professional and technical personnel in this field.

[0023] Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments, or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the technical solution of the present invention.

Claims

1. A method for preparing a MEMS hydrogen sensor, characterized in that: Including hydrogen sensor and preparation method thereof; The hydrogen sensor comprises a base plate, a MEMS substrate, and a hydrogen sensitive material; The bottom plate is configured as a "U"-shaped PCB board with a hollow hole in the middle, four circuit terminals are respectively arranged at the four corners of one side of the bottom plate, and four screw holes are fixedly arranged at the centers of the four circuit terminals; a four-legged bracket is fixedly arranged on one side of the hollow hole in the middle of the bottom plate, and the four legs of the four-legged bracket are respectively connected to the four circuit terminals, and a pair of interdigital electrode circuits are fixedly arranged on two legs on a diagonal line and the corresponding two circuit connection terminals; The MEMS substrate is located in the middle of one side of the four-legged support and is configured as a micro-heated interdigital electrode composite silicon wafer. A pair of interdigital electrode circuits on the four-legged support are connected to the interdigital electrode composite silicon wafer for power supply. The hydrogen sensitive material is arranged on the MEMS base layer, and includes three layers of metal oxide nano-sensitive film layers and a noble metal deposition layer; The three-layer metal oxide nano-sensitive film layer is sequentially arranged on the surface of the MEMS base layer as a tin dioxide sensitive film layer, a tin dioxide and zinc oxide composite sensitive film layer, and a nickel oxide sensitive film layer to form the three-layer metal oxide nano-sensitive film layer semiconductor, and the total thickness is set to 50 to 500 nanometers; The noble metal deposition layer is a palladium metal layer, which is deposited on the surface of the nickel oxide sensitive film layer.

2. The method for preparing a MEMS hydrogen sensor according to claim 1, characterized in that: The preparation method of the hydrogen sensor comprises: The preparation method of the tin dioxide sensitive film layer, the preparation method of the tin dioxide and zinc oxide composite sensitive film layer, the preparation method of the nickel oxide sensitive film layer, and the preparation method of the precious metal deposition layer; The preparation method of the tin dioxide sensitive film layer: Tin tetrachloride is the source of tin dioxide, ethanolamine is the reducing agent, and ethanol and deionized water are the solvents; the concentration of tin tetrachloride is 0.01-10M, the concentration of ethanolamine is 0.01-10M, the molar ratio of tin tetrachloride to ethanolamine is 1:1, and the mass ratio of ethanol to deionized water is 1:1; Further, 50 ml of ethanol and 50 ml of deionized water were added to the container in proportion, and then 0.075-7.5 ml of ethanolamine was added, and the mixture was stirred thoroughly. Then 0.075-7.5 ml of tin tetrachloride was added, and the mixture was stirred thoroughly. The mixture was heated to 30° C. to 90° C. and stirred with a magnetic stirrer until a transparent and slightly yellow solution was obtained, thereby obtaining the tin dioxide ink solution. Further, the tin dioxide ink is attached to the MEMS substrate by inkjet printing; Further, the bottom plate with the tin dioxide ink attached thereto is placed in a sintering furnace, and sintered at a high temperature of 200 to 500° C. to form the tin dioxide sensitive film layer, with a thickness of 10 to 200 nanometers; The preparation method of the composite sensitive film layer of tin dioxide and zinc oxide: Tin tetrachloride is the source of tin dioxide, zinc acetate dihydrate is the source of zinc oxide, ethanolamine is the reducing agent, and ethanol and deionized water are the solvents; wherein the concentration of tin tetrachloride is 0.01-10M, the concentration of zinc acetate dihydrate is 0.01-10M, the concentration of ethanolamine is 0.01-10M, the molar ratio of tin tetrachloride to zinc acetate dihydrate is 1-10:1, the molar ratio of tin tetrachloride and zinc acetate dihydrate to ethanolamine is 1:1, and the mass ratio of ethanol to deionized water is 1:1; Further, 50 ml of ethanol and 50 ml of deionized water are added to the container in proportion, followed by 0.1 to 10 ml of ethanolamine, and the mixture is stirred thoroughly. Then, 0.05 to 5 ml of tin tetrachloride and 0.05 to 5 ml of zinc acetate dihydrate are added, stirred thoroughly, heated to 30° C. to 90° C., and stirred magnetically until a transparent slightly yellow solution is obtained, thereby obtaining the tin dioxide and zinc oxide composite ink solution, wherein the ratio of tin dioxide to zinc oxide is 1 to 10:1; Furthermore, the tin dioxide and zinc oxide composite ink is attached to the sintered and fixed tin dioxide sensitive film layer by inkjet printing; Further, the bottom plate with the tin dioxide and zinc oxide composite ink attached thereto is placed in a sintering furnace, and sintered at a high temperature of 300 to 500° C. to form the tin dioxide and zinc oxide composite sensitive film layer, with a thickness of 10 to 100 nanometers; The preparation method of the nickel oxide sensitive film layer: Nickel chloride hexahydrate is the source of nickel oxide, ethanolamine is the reducing agent, and ethanol and deionized water are the solvents; wherein the concentration of nickel chloride hexahydrate is 0.01-10M, the concentration of ethanolamine is 0.01-10M, the molar ratio of ethanolamine to nickel chloride hexahydrate is 1:1, and the mass ratio of ethanol to deionized water is 1:1; Further, 50 ml of ethanol and 50 ml of deionized water are added to the container in proportion, and then 0.05-5 ml of ethanolamine is added, and the mixture is stirred thoroughly. Then 0.05-5 ml of nickel chloride hexahydrate is added, and the mixture is stirred thoroughly. The mixture is heated to 30° C. to 90° C. and stirred with a magnetic force until a transparent green solution is obtained, thereby obtaining the nickel oxide ink solution. Furthermore, the nickel oxide ink is attached to the sintered and fixed tin dioxide and zinc oxide composite sensitive film layer by inkjet printing; Furthermore, the bottom plate with the nickel oxide ink attached thereto is placed in a sintering furnace and sintered at a high temperature of 300 to 500° C. to form the nickel oxide sensitive film layer with a thickness of 1 to 100 nanometers. A method for preparing the noble metal deposit layer; Palladium chloride is the source of palladium, ethanol and deionized water are solvents, and the concentration of palladium chloride is 0.001-0.1 M; Further, 50 ml of ethanol and 50 ml of deionized water were added to the container in proportion, and then 0.005-0.5 ml of palladium chloride was added and stirred thoroughly to prepare a palladium ink solution; Furthermore, the palladium ink is attached to the sintered and fixed nickel oxide sensitive film layer by inkjet printing. Further, the base plate with the palladium ink attached thereto is placed in a sintering furnace, and sintered at a high temperature of 300 to 500° C. to form the palladium metal layer, with a thickness of 0.1 to 100 nanometers; Finally, an ultrasonic bonding machine is used to bond the gold wires to form the hydrogen sensor.

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