NO2 gas detection device based on giant magnetoresistive sensor and preparation method of NO2 gas detection device

Abstract

The invention discloses a giant magnetoresistive sensor-based NO2 gas detection device and a preparation method thereof, and relates to the technical field of magnetic sensors, the giant magnetoresistive sensor-based NO2 gas detection device comprises: a test chamber having a gas inlet and a gas outlet, the upper and lower surfaces of the test chamber being respectively provided with permanent magnets; the giant magnetoresistance chip is arranged in the test chamber, and the direction of a magnetic field formed by the permanent magnet vertically penetrates through the giant magnetoresistance chip; an MOFs film is arranged on the surface of the giant magnetoresistance chip. According to the invention, high-selectivity detection of the NO2 gas can be realized by means of the giant magnetoresistance sensor by utilizing the inherent paramagnetic characteristic of the NO2 gas; the giant magnetoresistive sensor is combined with the gas sensitive material MOFs, so that the sensitivity response to NO2 can be greatly improved; by adopting the MEMS technology, the miniaturization of the whole detection device is realized; each sensor can work independently and can also be connected in series or in parallel to form a sensing array, so that the sensitivity and selectivity of the sensor to NO2 gas are further improved; the whole sensor is simple in structure and easy to integrate, and has a good application prospect and a wide application range.

Description

Technical Field

[0001] The present invention relates to the technical field of magnetic sensors, and in particular to a NO2 gas detection device based on a giant magnetoresistance sensor and a preparation method thereof. Background Art

[0002] Monitoring nitrogen dioxide gas is of great significance to human health, environmental protection, etc. Rapid qualitative identification and quantitative judgment can help people take targeted measures quickly to avoid greater harm.

[0003] Nitrogen dioxide gas has the characteristics of dispersed points, wide distribution, and large emission, which makes it difficult to detect, monitor, and judge. At present, the qualitative detection and identification of nitrogen dioxide gas mostly adopts traditional metal oxide semiconductor sensor detection technology. This technology is based on chemical adsorption of oxygen adsorption and desorption characteristics, which is generally temperature-dependent, has poor performance at room temperature, and is easily affected by humidity in the environment.

[0004] Magnetic sensors are sensors that use magnetic sensitive elements to convert magnetic signals into electrical signals. Among them, giant magnetoresistance sensors are widely used in many industries such as water conservancy and hydropower, railway transportation, intelligent buildings, production automation, and aerospace due to their high sensitivity, simple structure, small size, easy integration, and low cost. Nitrogen dioxide is a paramagnetic gas, and it is feasible to use giant magnetoresistance sensors to detect changes in magnetic signals caused by nitrogen dioxide gas, and giant magnetoresistance sensors can avoid being affected by temperature and humidity.

[0005] In view of this, how to provide a new nitrogen dioxide gas sensor based on a magnetic sensor is a problem that technical personnel in this field need to solve urgently. Summary of the invention

[0006] The purpose of the present invention is to provide a NO2 gas detection device based on a giant magnetoresistance sensor and a preparation method thereof, so as to solve the problems existing in the prior art.

[0007] To achieve the above object, the present invention provides the following solution: The present invention provides a NO2 gas detection device based on a giant magnetoresistance sensor, comprising:

[0008] The test chamber is made of non-magnetic material and has an air inlet and an air outlet. Permanent magnets are respectively installed on the upper and lower surfaces of the test chamber;

[0009] A giant magnetoresistance chip is arranged in the test chamber, and the magnetic field formed by the permanent magnet passes vertically through the giant magnetoresistance chip.

[0010] Furthermore, a MOFs film is arranged on the surface of the giant magnetoresistive chip.

[0011] Furthermore, the giant magnetoresistive chip includes: a silicon wafer; and a first Ta layer, an IrMn layer, a CoFe layer, a Ru layer, a CoFe layer, a Cu layer, a CoFe layer, a NiFe layer and a second Ta layer stacked in sequence from bottom to top on the silicon wafer.

[0012] Furthermore, the thicknesses of the first Ta layer, IrMn layer, CoFe layer, Ru layer, CoFe layer, Cu layer, CoFe layer, NiFe layer and the second Ta layer are 2.6nm, 6nm, 2.8nm, 1.5nm, 2.8nm, 2.4nm, 6.2nm and 2.9nm respectively; the thickness of the MOFs film is 1μm.

[0013] The present invention also provides a method for preparing a NO2 gas detection device based on a giant magnetoresistance sensor, comprising the following steps:

[0014] S1: forming a first Ta layer, an IrMn layer, a CoFe layer, a Ru layer, a CoFe layer, a Cu layer, a CoFe layer, a NiFe layer and a second Ta layer on a silicon wafer in sequence by magnetron sputtering to obtain a giant magnetoresistive wafer;

[0015] S2: spin coating the outer surface of the giant magnetoresistive wafer to form a MOFs thin film to obtain a MOFs thin film wafer;

[0016] S3: Giant magnetoresistance chip is made using MEMS on MOFs thin film wafer.

[0017] Furthermore, the specific steps of step S2 are: after mixing the metal ion source compound and the organic ligand, adding an acid modulator to react to obtain a MOFs solution containing monodisperse MOFs nanoparticles, the reaction temperature is 120°C, and the reaction time is 12-24h; spin coating the MOFs solution on the outer surface of the giant magnetoresistive wafer to form a MOFs film.

[0018] Furthermore, the metal ion source compound is ZrCl4; the organic ligand is terephthalic acid; the acid modulator is acetic acid; the molar ratio of the metal ion in the metal ion source compound to the organic ligand is 1:1-1:80, and the added amount of the acid modulator is 0M-5M.

[0019] Furthermore, the rotation speed of the MOFs solution spin coating is 3000-4000 r / min, the working time is 30s-1min, and the concentration of the MOFs solution is 50-100 mg / ml.

[0020] Furthermore, the specific steps of step S3 are:

[0021] S301: Cleaning MOFs thin film wafer;

[0022] S302: A layer of positive photoresist is spin-coated on the surface of the MOFs thin film wafer, and after pre-baking, exposure, development and IBE etching, the required tortuous magnetoresistance pattern is obtained to make a giant magnetoresistance chip.

[0023] Furthermore, a plurality of the giant magnetoresistive chips form a Wheatstone bridge.

[0024] The present invention discloses the following technical effects:

[0025] The present invention utilizes the inherent paramagnetic characteristics of NO2 gas and can achieve highly selective detection of NO2 gas with the help of giant magnetoresistance sensors; the giant magnetoresistance sensor is combined with the gas sensitive material MOFs to greatly improve its sensitivity response to NO2; the MEMS technology is used to achieve miniaturization of the entire detection device; each sensor can work independently or be connected in series or in parallel to form a sensor array to further improve its sensitivity and selectivity to NO2 gas; the entire sensor has a simple structure, is easy to integrate, and has good application prospects and a wide range of applicability. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0027] Figure 1 This is a schematic diagram of a giant magnetoresistance chip;

[0028] Figure 2 The circuit diagram of the Wheatstone bridge structure composed of four giant magnetoresistive chips;

[0029] Figure 3 This is a schematic diagram of the test room;

[0030] Figure 4 The test result of NO2 by the detection device;

[0031] Figure 5 Schematic diagram of the effect of temperature on the performance of the detection device;

[0032] Figure 6 Schematic diagram of the effect of humidity on the performance of the detection device.

[0033] Among them, 1. giant magnetoresistance chip; 2. test chamber; 3. air inlet; 4. air outlet; 5. MOFs film; 6. upper cover; 7. lower cover; 8. permanent magnet. DETAILED DESCRIPTION

[0034] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0035] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0036] The embodiment of the present invention provides a NO2 gas detection device based on a giant magnetoresistive sensor, comprising: a test chamber 2, an air inlet 3 and an air outlet 4 are respectively arranged on the left and right sides, the air inlet 3 and the air outlet 4 are respectively connected to the air inlet pipe and the air outlet pipe, the test chamber 2 has an upper cover 6 and a lower cover 7 (the test chamber 2, the upper and lower covers 7 are all made of non-magnetic materials, such as glass, etc.), and a permanent magnet 8 is installed on the outer surface of the upper cover 6 and the lower cover 7, and the permanent magnet 8 is made of CoCrP alloy. The size of the test chamber 2 is 200μm×200μm×400μm; the giant magnetoresistive chip 1 is arranged in the test chamber 2, and the magnetic field direction formed by the permanent magnet 8 passes through the giant magnetoresistive chip 1 vertically.

[0037] In this embodiment, a MOFs film 5 with a thickness of 1 μm is provided on the surface of the giant magnetoresistive chip 1. The MOFs material has a high specific surface area, which will significantly increase the number of adsorption sites for nitrogen dioxide molecules. Therefore, the introduction of MOFs can significantly improve the sensitivity of the sensor to nitrogen dioxide gas. The giant magnetoresistive chip 1 includes: a silicon wafer and a first Ta layer, an IrMn layer, a CoFe layer, a Ru layer, a CoFe layer, a Cu layer, a CoFe layer, a NiFe layer and a second Ta layer stacked from bottom to top on the silicon wafer. The thicknesses are 2.6nm, 6nm, 2.8nm, 1.5nm, 2.8nm, 2.4nm, 6.2nm and 2.9nm respectively.

[0038] The present invention also provides a method for preparing a NO2 gas detection device based on a giant magnetoresistance sensor, comprising the following steps:

[0039] S1: Giant magnetoresistance wafer preparation

[0040] S101: The silicon wafer coated with silicon dioxide is ultrasonically cleaned with acetone, ethanol and deionized water in turn, and blown dry with nitrogen. Then it is placed in the magnetron sputtering chamber and the pressure of the magnetron sputtering chamber is increased to 1.0*10 -6 Pa;

[0041] S102: 20 sccm of argon gas is introduced into the chamber, and the pressure of the sputtering chamber is adjusted to 0.5 Pa;

[0042] S103: Connect a DC power supply to each target, and sequentially sputter the first Ta layer, IrMn layer, CoFe layer, Ru layer, CoFe layer, Cu layer, CoFe layer, NiFe layer, and second Ta layer on the silicon wafer by magnetron sputtering. The sputtering times are 52, 120, 56, 30, 56, 60, 56, 154, and 57 seconds, respectively. The power of the Ru, Cu, and NiFe targets is 10W, and the power of the other targets is 15W. After the sputtering is completed, the giant magnetoresistive wafer is placed in a magnetic thermal annealing furnace at a pressure of 1.0*10 -6 Pa, annealing at 275℃ for 15min.

[0043] S2: MOFs thin film 5 wafer preparation

[0044] S201: After mixing the metal ion source compound and the organic ligand, an acid modulator is added to react, wherein the metal ion source compound is ZrCl4; the organic ligand is terephthalic acid; the acid modulator is acetic acid; a MOFs solution containing monodisperse MOFs nanoparticles is obtained, the reaction temperature is 120°C, and the reaction time is 12-24h; in the above process, the molar ratio of MOFs metal ions to organic ligands and the amount of acid modulator added are continuously adjusted to determine the optimal experimental parameters and prepare highly monodisperse MOFs nanoparticles; the molar ratio of metal ions to organic ligands in the metal ion source compound is 1:1-1:32; the amount of acid modulator added is 1M-2M.

[0045] S202: Spin coating the outer surface of the giant magnetoresistive wafer to form a MOFs thin film 5, thereby obtaining a wafer of MOFs thin film 5. The rotation speed of the MOFs solution spin coating is 3000-4000 r / min, the working time is 30s-1min, and the concentration of the MOFs solution is 50-100 mg / ml.

[0046] S3: Preparation of giant magnetoresistance chip 1

[0047] S301: Cleaning and drying the surface of the MOFs film 5 wafer;

[0048] S302: The MOFs thin film 5 wafer is precisely photolithographically processed by integrated circuit ultraviolet lithography, and positive photoresist (AZ5214) is spin-coated for 30 seconds at a spinning speed of 4000 r / min, and then the photoresist is baked at 80° C. for 15 minutes in a vacuum oven.

[0049] S303: Patterning and etching the MOFs film 5 wafer by plasma etching or other methods, removing some useless films, and obtaining a long strip giant magnetoresistive chip 1 with a tortuous shape.

[0050] S304: After the etching is completed, the photoresist is removed, the MOFs film 5 wafer is cut and diced, and then four giant magnetoresistive chips 1 are formed into a Wheatstone bridge structure as shown in FIG. Figure 2 As shown, R1, R2, R3, and R4 represent four giant magnetoresistive chips 1, which are packaged after assembly.

[0051] S4: Preparation of NO2 gas detection device

[0052] The giant magnetoresistive chip 1 is mounted at the bottom of the test chamber 2 , and permanent magnets 8 are mounted on the upper and lower surfaces of the test chamber 2 , respectively, so that the magnetic field direction of the permanent magnet 8 passes through the giant magnetoresistive chip 1 vertically.

[0053] The specific working process of the NO2 gas detection device is as follows:

[0054] However, when NO2 gas is introduced into the test chamber 2, the MOFs film 5 on the surface of the giant magnetoresistive chip 1 absorbs NO2 gas, forming a NO2 gas enriched gas layer on its surface; at the same time, the giant magnetoresistive chip 1 is located in a perpendicular magnetic field. Due to the enrichment of NO2, it will cause fluctuations in the magnetic field, and the giant magnetoresistive sensor is more sensitive to the magnetic field parallel to its surface, so it will identify fluctuations in the magnetic field parallel to its surface; specifically, it is manifested as a change in voltage, and the change in voltage is proportional to the change in NO2 gas concentration, so the NO2 gas concentration can be determined. The test results of different NO2 concentrations are shown in Figure 2. Figure 4 As shown, it shows good linearity. Figure 5 and 6 The test results of 5ppm NO2 at different temperatures and humidities are given. It can be seen that temperature and humidity have little effect on the performance of the detection device.

[0055] In the description of the present invention, it should be understood that the directions or positional relationships indicated by the terms “longitudinal”, “lateral”, “upper”, “lower”, “front”, “rear”, “left”, “right”, “vertical”, “horizontal”, “top”, “bottom”, “inner”, “outer”, etc. are based on the directions or positional relationships shown in the drawings.

[0056] This is for the purpose of describing the present invention, but it does not indicate or imply that the devices or elements mentioned must have a specific orientation, be constructed and operate in a specific orientation, and therefore it should not be understood as limiting the present invention.

[0057] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A NO2 gas detection device based on a giant magnetoresistance sensor, characterized in that: include: A test chamber (2) is made of non-magnetic material and has an air inlet (3) and an air outlet (4); permanent magnets (8) are respectively installed on the upper and lower surfaces of the test chamber (2); The giant magnetoresistance chip (1) is arranged in the test chamber (2), and the direction of the magnetic field formed by the permanent magnet (8) passes through the giant magnetoresistance chip (1) vertically.

2. A NO2 gas detection device based on a giant magnetoresistance sensor according to claim 1, characterized in that: A MOFs thin film (5) is arranged on the surface of the giant magnetoresistive chip (1).

3. A NO2 gas detection device based on a giant magnetoresistance sensor according to claim 2, characterized in that: The giant magnetoresistive chip (1) comprises: Silicon wafer; And a first Ta layer, an IrMn layer, a CoFe layer, a Ru layer, a CoFe layer, a Cu layer, a CoFe layer, a NiFe layer and a second Ta layer are stacked in sequence from bottom to top on the silicon wafer.

4. A NO2 gas detection device based on a giant magnetoresistance sensor according to claim 3, characterized in that: The thicknesses of the first Ta layer, IrMn layer, CoFe layer, Ru layer, CoFe layer, Cu layer, CoFe layer, NiFe layer and the second Ta layer are 2.6 nm, 6 nm, 2.8 nm, 1.5 nm, 2.8 nm, 2.4 nm, 6.2 nm and 2.9 nm respectively; the thickness of the MOFs film (5) is 1 μm.

5. A method for preparing a NO2 gas detection device based on a giant magnetoresistance sensor, characterized in that: The following steps are involved: S1: forming a first Ta layer, an IrMn layer, a CoFe layer, a Ru layer, a CoFe layer, a Cu layer, a CoFe layer, a NiFe layer and a second Ta layer on a silicon wafer in sequence by magnetron sputtering to obtain a giant magnetoresistive wafer; S2: forming a MOFs thin film (5) by spin coating on the outer surface of the giant magnetoresistive wafer to obtain a MOFs thin film (5) wafer; S3: A giant magnetoresistive chip (1) is manufactured on a MOFs thin film (5) wafer using MEMS.

6. The method for preparing a NO2 gas detection device based on a giant magnetoresistance sensor according to claim 5, characterized in that: The specific steps of step S2 are: after mixing the metal ion source compound and the organic ligand, adding an acid modulator to react to obtain a MOFs solution containing monodispersed MOFs nanoparticles, the reaction temperature is 120° C., and the reaction time is 12-24 hours; spin coating the MOFs solution on the outer surface of the giant magnetoresistive wafer to form a MOFs film (5).

7. The method for preparing a NO2 gas detection device based on a giant magnetoresistance sensor according to claim 6, characterized in that: The metal ion source compound is ZrCl4; the organic ligand is terephthalic acid; the acid modulator is acetic acid; the molar ratio of the metal ion in the metal ion source compound to the organic ligand is 1:1-1:80, and the added amount of the acid modulator is 0M-5M.

8. The method for preparing a NO2 gas detection device based on a giant magnetoresistance sensor according to claim 6, characterized in that: The rotation speed of the MOFs solution spin coating is 3000-4000r / min, the working time is 30s-1min, and the concentration of the MOFs solution is 50-100mg / ml.

9. The method for preparing a NO2 gas detection device based on a giant magnetoresistance sensor according to claim 5, characterized in that: The specific steps of step S3 are: S301: Cleaning the MOFs film (5) wafer; S302: Spin-coating a layer of positive photoresist on the surface of the MOFs thin film (5) wafer, and performing pre-baking, exposure, development and IBE etching to obtain the required tortuous magnetoresistive pattern, thereby manufacturing a giant magnetoresistive chip (1).

10. The method for preparing a NO2 gas detection device based on a giant magnetoresistance sensor according to claim 9, characterized in that: A plurality of giant magnetoresistive chips (1) form a Wheatstone bridge.

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