MEMS carbon monoxide sensor gas sensitive film and preparation method thereof

Abstract

The invention discloses a method for preparing a gas-sensitive film of a MEMS carbon monoxide sensor, comprising the following steps: S1: installing a tin dioxide target material and a gold target material on different magnetron sputtering targets of a magnetron sputtering instrument respectively, connecting high-purity argon gas to the air inlet of the magnetron sputtering instrument, placing a micro-heating plate in the magnetron sputtering instrument, and adjusting the sputtering distance H between the magnetron sputtering target and the micro-heating plate; S2: selecting a tin dioxide target material as a working target material of the magnetron sputtering instrument, turning on the main power supply of the magnetron sputtering instrument, starting to evacuate, and adjusting the air pressure of the vacuum chamber to 5*10 ‑3 Pa, set the temperature of the micro-heating plate to 25°C; S3: turn on the radio frequency sputtering power supply to start plating a tin dioxide film on the surface of the micro-heating plate; S4: after the tin dioxide film is plated, a gold film is plated on the surface of the tin dioxide film; after the gold film is plated, a gold-modified tin dioxide gas-sensitive film is obtained. The present invention can improve the response sensitivity and stability of the MEMS carbon monoxide sensor, and can mass-produce MEMS carbon monoxide sensors.

Description

Technical Field

[0001] The present invention relates to the technical field of gas sensors, and in particular to a gas-sensitive film of a MEMS carbon monoxide sensor and a preparation method thereof. Background Art

[0002] Gas sensors can be generally divided into semiconductor gas sensors, electrochemical gas sensors, solid electrolyte gas sensors, catalytic combustion gas sensors, etc. according to their gas-sensing properties. Among them, semiconductor gas sensors are the most commonly used and most practical type of gas sensors. Gas sensors mainly rely on gas-sensitive films to detect target gases. For example, the gas-sensitive film of a carbon monoxide sensor can be a tin dioxide gas-sensitive film.

[0003] MEMS micro-heating plate sensors are the most advanced type of gas sensors currently used. MEMS, or micro-electromechanical system, is a multidisciplinary frontier research field developed on the basis of microelectronics technology. Compared with traditional gas sensors, it has the characteristics of small size, light weight, low cost, low power consumption, high reliability, suitable for mass production, easy integration and intelligence, and can achieve feature sizes in the micrometer range.

[0004] At present, the method for preparing the gas-sensitive film of the same carbon sensor mainly includes the solution method. For example, the Chinese patent with the publication number CN111982981A discloses a SnO2-based gas-sensitive material, which is doped with Pd, Si and Sb elements on the basis of SnO2. The preparation method of the SnO2-based gas-sensitive material is as follows: (1) preparing a tin tetrachloride aqueous solution, placing a palladium chloride solution and an antimony trichloride solution in the tin tetrachloride solution, and continuing to add a tetraethyl orthosilicate solution and stirring; (2) adding a urea aqueous solution to the solution of step (1), stirring and transferring the solution to a high-temperature reactor with a polytetrafluoroethylene liner for hydrothermal reaction, and then naturally cooling to room temperature to obtain a hydrothermal product; (3) purifying the hydrothermal product to obtain the SnO2-based gas-sensitive material. After the SnO2-based gas-sensitive material is prepared, it is transferred to the MEMS micro-heating plate. Although the sensitivity of the gas sensor of this patent is improved, the preparation process is complicated and time-consuming, and the bonding degree between the gas-sensitive material and the micro-heating plate is not high, and the gas-sensitive material is easy to fall off after long-term use. Summary of the invention

[0005] The technical problem to be solved by the present invention is: in order to solve the technical problems that the method for preparing the gas-sensitive film of the MEMS carbon monoxide sensor in the prior art is complicated and time-consuming, and the adhesion between the gas-sensitive film and the micro-heating plate is poor. The present invention provides a MEMS carbon monoxide sensor gas-sensitive film and a preparation method thereof, wherein a tin dioxide film is deposited on the surface of the micro-heating plate by a sputtering method, and at the same time, the tin dioxide film is modified by gold elements, so that the stability and responsiveness of the gas-sensitive film can be improved.

[0006] The technical solution adopted by the present invention to solve the technical problem is: a method for preparing a gas-sensitive film of a MEMS carbon monoxide sensor, comprising the following steps:

[0007] S1: Install the tin dioxide target and the gold target on different magnetron sputtering targets of the magnetron sputtering instrument respectively, connect high-purity argon gas to the air inlet of the magnetron sputtering instrument, put the micro-heating plate into the magnetron sputtering instrument, adjust the sputtering distance H between the magnetron sputtering target and the micro-heating plate, close the chamber door and the air release valve of the magnetron sputtering instrument, and turn off the flow meter;

[0008] S2: Select the tin dioxide target as the working target of the magnetron sputtering instrument, turn on the main power of the magnetron sputtering instrument, start the mechanical pump and open the stop valve to start vacuuming. When the vacuum chamber pressure drops below 7Pa, turn on the molecular pump working button. When the molecular pump is stable, adjust the vacuum chamber pressure to 5*10 -3 Pa below, set the temperature of the micro-heating plate to 25 °C;

[0009] S3: Turn on the pressure regulating switch, open the air inlet valve, turn on the flow meter, introduce argon gas and adjust the air pressure in the vacuum chamber to 0.1Pa-10Pa, turn on the RF sputtering power supply to start plating a tin dioxide film on the surface of the micro-heating plate;

[0010] S4: After the tin dioxide film is plated, turn off the RF sputtering power supply, the flow meter, the air inlet valve and the voltage regulator, replace the working target of the magnetron sputtering instrument with a gold target, and readjust the air pressure in the vacuum chamber to 5*10 -3 Pa, open the pressure regulating switch, air inlet valve and flowmeter again, introduce argon gas and adjust the air pressure in the vacuum chamber to 0.1Pa-10Pa, turn on the radio frequency sputtering power supply to start plating a gold film on the surface of the tin dioxide film; after the gold film plating is completed, a gold-modified tin dioxide gas-sensitive film is obtained.

[0011] Furthermore, when plating the tin dioxide film, the power of the RF sputtering power supply is set to 20W-100W, and the sputtering time is set to 0.5-5 hours. The greater the power, the faster the sputtering speed, the longer the time, and the thicker the sputtered film. In order to make the thickness of the tin dioxide film within a suitable range, the power and sputtering time need to be controlled, and the two need to cooperate with each other. The thickness of the tin dioxide film will affect the sensitivity and range of the MEMS carbon monoxide sensor.

[0012] Furthermore, when the gold film is plated, the power of the RF sputtering power supply is set to 20W-100W, and the sputtering time is set to 5-60 seconds. The greater the power, the faster the sputtering speed, the longer the time, and the thicker the sputtered film. In order to make the thickness of the gold film within a suitable range, the power and sputtering time need to be controlled, and the two need to cooperate with each other. The thickness of the gold film cannot be too thick, otherwise it will not be able to improve the sensitivity of the carbon monoxide sensor.

[0013] Furthermore, the thickness of the tin dioxide film is 500-1500 nm. Under this thickness, the stability, sensitivity and range of the obtained carbon monoxide sensor are improved.

[0014] Furthermore, the thickness of the gold film is 1-10nm. The thickness of the gold film is related to the sensitivity of the sensor. If the gold film is too thick, the tin dioxide film and the carbon monoxide gas cannot fully contact each other, and the sensitivity of the sensor cannot be improved; if the gold film is too thin, the tin dioxide film and the carbon monoxide gas cannot fully react, and the sensitivity of the sensor cannot be improved.

[0015] Furthermore, in order to achieve better uniformity of the deposited thin film, the sputtering distance H between the magnetron sputtering target and the micro-heating plate is 50-200 mm.

[0016] Furthermore, the flow rate of the argon gas is 10-50 sccm. Argon gas is an inert gas and will not react with the target material, and is only used to adjust the gas pressure in the vacuum chamber.

[0017] A MEMS carbon monoxide sensor gas-sensitive film is obtained by the above-mentioned method for preparing the MEMS carbon monoxide sensor gas-sensitive film. The MEMS carbon monoxide sensor gas-sensitive film is a layered structure, including a tin dioxide film and a gold film. The gold film is attached to the surface of the tin dioxide film by sputtering.

[0018] Furthermore, the gold film covers part of the surface of the tin dioxide film. The gold film modification of the tin dioxide film has two functions: on the one hand, gold is a good catalyst, which can help carbon monoxide gas adsorb on the surface of the tin dioxide film; on the other hand, gold is a high-quality conductor, which can enhance the conductivity of the tin dioxide film. In other words, the gold film is randomly dispersed on the surface of the tin dioxide film, and the gold film can play a certain catalytic role in the reaction between tin dioxide and carbon monoxide gas. The gold film only covers part of the surface of the tin dioxide film, which can further improve the sensitivity of the gas-sensitive film to carbon monoxide gas, and is more conducive to improving the sensitivity of the MEMS carbon monoxide sensor.

[0019] The beneficial effects of the present invention are as follows:

[0020] The invention adopts magnetron sputtering to sputter a gold-modified tin dioxide gas-sensitive film on a micro-heating plate, which can improve the adhesion between the gas-sensitive film and the micro-heating plate, is not easy to fall off, can be prepared in batches, and can improve work efficiency. The gas-sensitive film of the invention is based on tin dioxide and is modified with gold elements, which can significantly improve the sensitivity of the MEMS carbon monoxide gas sensor and has good stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0022] Figure 1 The present invention is a flow chart of a method for preparing a gas-sensitive film of a MEMS carbon monoxide sensor.

[0023] Figure 2 It is a schematic structural diagram of the gold-modified tin dioxide gas-sensitive film of the present invention.

[0024] Figure 3 3 is a sensitivity change diagram of the CO sensors prepared in Examples 1 to 3 of the present invention.

[0025] Figure 4 It is a sensitivity change diagram of the CO sensors of Comparative Example 1, Example 2, and Example 4 of the present invention.

[0026] Figure 5 This is a SEM scan of the gas-sensitive film of Example 2 of the present invention.

[0027] Figure 6 This is an elemental analysis diagram of the gold-modified tin dioxide thin film of the present invention.

[0028] In the figure: 10, tin dioxide film, 20, gold film. DETAILED DESCRIPTION

[0029] The present invention will now be described in further detail with reference to the accompanying drawings. These drawings are simplified schematic diagrams, which only illustrate the basic structure of the present invention in a schematic manner, and therefore only show the components related to the present invention.

[0030] like Figure 1 As shown, a method for preparing a gas-sensitive film of a MEMS carbon monoxide sensor comprises the following steps:

[0031] S1: Install the tin dioxide target and the gold target on different magnetron sputtering targets of the magnetron sputtering instrument respectively, connect high-purity argon gas to the air inlet of the magnetron sputtering instrument, put the micro-heating plate into the magnetron sputtering instrument, adjust the sputtering distance H between the magnetron sputtering target and the micro-heating plate, close the chamber door and the vent valve of the magnetron sputtering instrument, and turn off the flow meter.

[0032] S2: Select the tin dioxide target as the working target of the magnetron sputtering instrument, turn on the main power of the magnetron sputtering instrument, start the mechanical pump and open the stop valve to start vacuuming. When the vacuum chamber pressure drops below 7Pa, turn on the molecular pump working button. When the molecular pump is stable, adjust the vacuum chamber pressure to 5*10 -3 Pa below, set the temperature of the micro-hotplate to 25 °C.

[0033] S3: Turn on the pressure regulating switch, open the air inlet valve, turn on the flow meter, introduce argon gas and adjust the air pressure in the vacuum chamber to 0.1Pa-10Pa, turn on the RF sputtering power supply to start plating a tin dioxide film on the surface of the micro-heating plate.

[0034] S4: After the tin dioxide film is plated, turn off the RF sputtering power supply, the flow meter, the air inlet valve and the voltage regulator, replace the working target of the magnetron sputtering instrument with a gold target, and readjust the air pressure in the vacuum chamber to 5*10 -3 Pa, open the pressure regulating switch, air inlet valve and flowmeter again, introduce argon gas and adjust the air pressure in the vacuum chamber to 0.1Pa-10Pa, turn on the radio frequency sputtering power supply to start plating a gold film on the surface of the tin dioxide film; after the gold film plating is completed, a gold-modified tin dioxide gas-sensitive film is obtained.

[0035] In this embodiment, the gold-modified tin dioxide gas-sensitive film can improve the sensitivity of the MEMS carbon monoxide gas sensor in detecting carbon monoxide gas. The simple tin dioxide film has a high resistance, resulting in poor conductivity and insufficient reaction with carbon monoxide gas. The gold-modified tin dioxide film can increase free electrons, react with more carbon monoxide gas, and improve the conductivity of the tin dioxide film. In addition, compared with other metals with good conductivity (copper, aluminum, etc.), gold has better stability and is not easily oxidized. The purity of gold is preferably 99.999%.

[0036] In the present embodiment, when the tin dioxide film is plated, the power of the radio frequency sputtering power supply is set to 20W-100W, and the sputtering time is set to 0.5-5 hours. The greater the power of the radio frequency sputtering power supply, the faster the sputtering speed, the longer the sputtering time, and the thicker the deposited film. Preferably, the uniformity of the thickness of the obtained tin dioxide film meets the requirements when sputtering for 0.5-1.5 hours under the condition of 50W power. The thickness of the obtained tin dioxide film is, for example, 500-1500nm.

[0037] In this embodiment, when the gold film is plated, the power of the RF sputtering power supply is set to 20W-100W, and the sputtering time is set to 5-60 seconds. Similarly, the greater the power of the RF sputtering power supply, the faster the sputtering speed, the longer the sputtering time, and the thicker the deposited film. Preferably, the sputtering is performed for 10-30 seconds under a power condition of 50W, and the thickness of the obtained gold film is 2-10nm. The gold film only needs to be deposited in a thin layer on the surface of the tin dioxide film. Since the sputtering speed and the sputtering time are coordinated with each other, therefore, if the sputtering power is too large and the sputtering speed is too fast, then the sputtering time may only take a few seconds or even shorter. If the sputtering time is too short, the error of time control will increase. For example, if the sputtering time only takes 3 seconds, it may not be accurately controlled within 3 seconds, which will cause the thickness of the gold film to increase and affect the sensitivity of the sensor. Therefore, in this embodiment, the preferred sputtering power is 50 W and the sputtering time is 10-30 seconds. On the one hand, the sputtering accuracy can be guaranteed, and on the other hand, the stability of the gold-modified tin dioxide gas-sensitive film and the sensitivity of the sensor can be improved.

[0038] In this embodiment, the sputtering distance H between the magnetron sputtering target and the micro-heating plate is 50-200 mm, and the flow rate of the argon gas is 10-50 sccm.

[0039] like Figure 2 As shown, the MEMS carbon monoxide sensor gas-sensitive film obtained by the preparation method of the present invention is a layered structure, including a tin dioxide film 10 and a gold film 20, and the gold film 20 is attached to the surface of the tin dioxide film 10 by sputtering. The gold film 20 covers part of the surface of the tin dioxide film 10. The thicker the tin dioxide film 10 is, the more carbon monoxide gas can react with it. Correspondingly, the thickness of the gold film will increase with the increase of the thickness of the tin dioxide film, so that the sensitivity of the MEMS titanium monoxide sensor is always maintained at a better level.

[0040] Example 1

[0041] Check whether all valves of the magnetron sputtering instrument are in the initial setting state, and ensure that the vacuum chamber is in a closed state before evacuating the vacuum. Make sure that the cooling water is connected before the magnetron sputtering instrument is powered on. Start the main power of the magnetron sputtering instrument, and switch the "water cut-off alarm" button to the "alarm" state. Connect high-purity argon gas to the air inlet of the magnetron sputtering instrument, open the argon gas cylinder, open the vent valve, and close the vent valve after it stabilizes. Open the chamber door of the magnetron sputtering instrument, put in the tin dioxide target and micro-heating plate, adjust the sputtering distance H to 80mm, and close the chamber door. Turn on the mechanical pump and the stop valve, start evacuating the vacuum chamber. When the air pressure in the vacuum chamber drops below 7Pa, turn on the molecular pump working button. When the molecular pump is stable, adjust the air pressure in the vacuum chamber to 5*10 -3 Pa, set the temperature of the micro-heating plate to 25 ° C. Turn on the pressure regulating switch, open the air inlet valve, and after about 10 seconds, turn on the flow meter, set the flow rate to 35 sccm, introduce argon gas and adjust the pressure in the vacuum chamber to about 1 Pa and stabilize it. Adjust the baffle to the shielding state, start the RF sputtering power supply, set the power to 50W, and after the RF sputtering power supply is stable, open the baffle to start plating a tin dioxide film on the surface of the micro-heating plate. The sputtering time is 0.5 hours, and a pure tin dioxide film can be obtained.

[0042] After the tin dioxide film is plated, turn off the RF sputtering power supply, the flow meter, the air inlet valve and the voltage regulator, replace the working target of the magnetron sputtering instrument with a gold target, and readjust the air pressure in the vacuum chamber to 5*10 -3 Pa, open the pressure regulating switch, air inlet valve and flowmeter again, set the flow rate to 35sccm, introduce argon gas and adjust the pressure in the vacuum chamber to about 1Pa and stabilize it. Adjust the baffle to the shielding state, start the RF sputtering power supply, set the power to 50W, and after the RF sputtering power supply is stable, open the baffle to start plating a gold film on the surface of the micro-heating plate. The sputtering time is 15 seconds. After the sputtering is completed, a gold-modified tin dioxide gas-sensitive film can be obtained.

[0043] Example 2

[0044] The difference between this embodiment and embodiment 1 is that the sputtering time of the tin dioxide film is 1 hour.

[0045] Example 3

[0046] The difference between this embodiment and embodiment 1 is that the sputtering time of the tin dioxide film is 1.5 hours.

[0047] Example 4

[0048] The difference between this embodiment and embodiment 1 is that the sputtering time of the tin dioxide film is 1.5 hours, and the sputtering time of the gold film is 30 seconds.

[0049] Example 5

[0050] The difference between this embodiment and embodiment 1 is that the sputtering time of the tin dioxide film is 1 hour, and the sputtering time of the gold film is 30 seconds.

[0051] Comparative Example 1

[0052] Check whether all valves of the magnetron sputtering instrument are in the initial setting state, and ensure that the vacuum chamber is closed before vacuuming. Ensure that the cooling water is connected before the magnetron sputtering instrument is powered on. Start the main power of the magnetron sputtering instrument and switch the "water cut alarm" button to the "alarm" state. Connect high-purity argon gas to the air inlet of the magnetron sputtering instrument, open the argon gas cylinder, open the vent valve, and close the vent valve after stabilization. Open the chamber door of the magnetron sputtering instrument, put in the tin dioxide target and micro-heating plate, adjust the sputtering distance H to 80mm, and close the chamber door. Turn on the mechanical pump and the stop valve, start vacuuming, and when the vacuum chamber pressure drops below 7Pa, turn on the molecular pump working button. When the molecular pump is stable, adjust the vacuum chamber pressure to below 5*10-3Pa, and set the temperature of the micro-heating plate to 25℃. Turn on the pressure regulating switch, open the air inlet valve, and after about 10 seconds, turn on the flow meter, set the flow rate to 35sccm, introduce argon gas and adjust the pressure in the vacuum chamber to about 1Pa and stabilize it. Adjust the baffle to the shielding state, start the RF sputtering power supply, set the power to 50W, and after the RF sputtering power supply stabilizes, open the baffle to start plating a tin dioxide film on the surface of the micro-heating plate. The sputtering time is 1.5 hours, and a pure tin dioxide film can be obtained.

[0053] The gas-sensitive films obtained in Examples 1-5 and Comparative Example 1 were used to prepare MEMS carbon monoxide sensors, and the sensitivity of these five MEMS carbon monoxide sensors was tested. The sensitivity in the present invention refers to the degree of change in the resistance of the gas-sensitive film of the gas sensor due to changes in the concentration of the target gas. The sensitivity of the present invention is expressed by the resistance ratio method, and the resistance ratio refers to the ratio of the resistance Rg of the gas-sensitive film in the target gas to the resistance Ro of the gas-sensitive film in the air S = Rg / Ro (S can be directly expressed as a ratio or as a percentage). The test results are as follows Figure 3 As shown (measured carbon monoxide concentration range of 0-1000ppm).

[0054] from Figure 3 It can be seen that at room temperature, by comparing Examples 1-3, the sensitivity of the MEMS carbon monoxide sensor of Example 2 is the highest. At 1000ppm, the sensitivity of the sensor can reach about 3.5 (350%), indicating that the film thickness of the tin dioxide film obtained by sputtering for 1 hour is better. At this time, the thickness of the tin dioxide film is 1μm. Please refer to Figure 3 and 4By comparing Examples 4 and 5, it can be seen that the sensitivity of the MEMS carbon monoxide sensor of Example 5 is higher than that of the MEMS carbon monoxide sensor of Example 4, indicating that even if the sputtering time of the gold film is increased, the sensitivity of the MEMS carbon monoxide sensor is still better when the tin dioxide film is sputtered for 1 hour. By comparing Example 2 and Example 5, it can be seen that when the sputtering time of the tin dioxide film is 1 hour, the effect of the gas-sensitive film obtained by sputtering the gold film for 15 seconds is better, and the sensitivity of the sensor is higher. The thickness of the gold film obtained by sputtering the gold film for 15 seconds is better, and the thickness of the gold film is 3nm at this time. The response time of the MEMS carbon monoxide sensor prepared in this embodiment is 8 seconds, and the response speed is fast. By comparing Example 2 and Comparative Example 1, it can be seen that the sensitivity of the sensor prepared by the gold-modified tin dioxide gas-sensitive film is significantly higher than the sensitivity of the sensor prepared by the simple tin dioxide gas-sensitive film, and the higher the carbon monoxide gas concentration, the more obvious the improvement in the sensitivity of the gold-modified tin dioxide gas-sensitive film. For example, at 1000 ppm, the sensitivity of the sensor of Example 2 is about 3.5, and the sensitivity of the sensor of Comparative Example 1 is about 1.5. The sensitivity of the sensor of Example 2 is improved by about 133%.

[0055] Figure 5 is a SEM image of the gold-modified tin dioxide film prepared in Example 2. Figure 5 It can be seen that the gold-modified tin dioxide film prepared by this method has good uniformity and consistency, and there are no obvious cracks, indicating that this method can successfully attach the gold film to the surface of the tin dioxide film.

[0056] Figure 6 This is the elemental analysis diagram of the gold-modified tin dioxide film. Figure 6 The presence of gold can be found in the film, indicating that the gold film is successfully attached to the surface of the tin dioxide film.

[0057] In summary, the present invention adopts magnetron sputtering to sputter a gold-modified tin dioxide gas-sensitive film on a micro-heating plate, which can improve the adhesion between the gas-sensitive film and the micro-heating plate, is not easy to fall off, and can be prepared in batches, which can improve work efficiency. In the prior art, although the preparation method is also adopted by magnetron sputtering, the prepared tin dioxide film is a strip, and its sensitivity when measuring carbon monoxide gas is only about 40%, and the measurement range is only 0-200ppm. The gas-sensitive film of the present invention is based on tin dioxide, and after being modified with gold elements, it can significantly improve the sensitivity of the MEMS carbon monoxide sensor, increase the measurement range of the MEMS carbon monoxide sensor (0-1000ppm), and has a fast response speed and good stability.

[0058] Based on the above ideal embodiments of the present invention, the relevant staff can make various changes and modifications without departing from the technical concept of the present invention through the above description. The technical scope of the present invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. A method for preparing a gas-sensitive film of a MEMS carbon monoxide sensor, characterized in that: The following steps are involved: S1: Install the tin dioxide target and the gold target on different magnetron sputtering targets of the magnetron sputtering instrument respectively, connect high-purity argon gas to the air inlet of the magnetron sputtering instrument, put the micro-heating plate into the magnetron sputtering instrument, adjust the sputtering distance H between the magnetron sputtering target and the micro-heating plate, and the sputtering distance H is 50-200mm; close the chamber door and the vent valve of the magnetron sputtering instrument, and turn off the flow meter; S2: Select the tin dioxide target as the working target of the magnetron sputtering instrument, turn on the main power of the magnetron sputtering instrument, start the mechanical pump and open the stop valve to start vacuuming. When the vacuum chamber pressure drops below 7Pa, turn on the molecular pump working button. When the molecular pump is stable, adjust the vacuum chamber pressure to 5*10 -3 Pa below, set the temperature of the micro-heating plate to 25 °C; S3: Turn on the pressure regulating switch, open the air inlet valve, turn on the flow meter, introduce argon gas and adjust the air pressure in the vacuum chamber to 0.1Pa-10Pa, turn on the radio frequency sputtering power supply to start plating a tin dioxide film on the surface of the micro-heating plate; when plating the tin dioxide film, the power of the radio frequency sputtering power supply is set to 20W-100W, and the sputtering time is set to 0.5-5 hours; the thickness of the tin dioxide film is 500-1500nm; S4: After the tin dioxide film is plated, turn off the RF sputtering power supply, the flow meter, the air inlet valve and the voltage regulator, replace the working target of the magnetron sputtering instrument with a gold target, and readjust the air pressure in the vacuum chamber to 5*10 -3 Pa, open the voltage regulating switch, air inlet valve and flowmeter again, introduce argon and adjust the air pressure in the vacuum chamber to 0.1Pa-10Pa, turn on the RF sputtering power supply to start plating a gold film on the surface of the tin dioxide film; the power of the RF sputtering power supply is set to 20W-100W, and the sputtering time is set to 5-60 seconds; the thickness of the gold film is 1-10nm; after the gold film is plated, a gold-modified tin dioxide gas-sensitive film is obtained.

2. The method for preparing the gas-sensitive film of the MEMS carbon monoxide sensor according to claim 1, characterized in that: The flow rate of argon gas is 10-50 sccm.

3. A MEMS carbon monoxide sensor gas sensitive film, characterized in that: The MEMS carbon monoxide sensor gas-sensitive film is obtained by the preparation method of any one of claims 1-2. The MEMS carbon monoxide sensor gas-sensitive film is a layered structure, including a tin dioxide film and a gold film, and the gold film is attached to the surface of the tin dioxide film by sputtering.

4. The MEMS carbon monoxide sensor gas sensitive film as claimed in claim 3, characterized in that: The gold film covers part of the surface of the tin dioxide film.

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