A precious metal-modified wafer-level MEMS gas sensor, its fabrication method and application

Abstract

This invention discloses a noble metal-modified wafer-level MEMS gas sensor, its fabrication method, and its application, belonging to the field of gas-sensitive thin film fabrication. The method includes: Step S1, fabricating a MEMS micro-heating plate array on a silicon wafer substrate; Step S2, fabricating a gas-sensitive thin film in the central region of each sensing unit of the MEMS micro-heating plate array; Step S3, uniformly depositing a noble metal on the surface of the gas-sensitive thin film to modify it, forming a MEMS gas sensor array; Step S4, subjecting the MEMS gas sensor array to air-hydrogen-air cycle high-temperature sintering annealing; Step S5, dicing and packaging the annealed MEMS gas sensor array to form a single MEMS gas sensor. The sensor fabricated by the method of this invention can simultaneously improve the sensitivity, consistency, and stability of MEMS gas sensors.

Description

Technical Field

[0001] This invention belongs to the field of gas-sensitive thin film preparation, and more specifically, relates to a noble metal-modified wafer-level MEMS gas sensor, its preparation method, and its application. Background Technology

[0002] Metal-oxide-semiconductor (MOS) gas sensors are resistive sensors that offer advantages over other types, including high sensitivity, fast response and recovery, all-solid-state operation, and small size, making them suitable for large-scale deployment at leak points. However, metal oxides as gas-sensitive materials suffer from drawbacks such as high operating temperatures and poor selectivity. To further improve the sensing performance for target gases, noble metal modification can be employed to regulate electron transfer direction, promote selective gas adsorption / dissociation, and optimize catalytic reaction pathways for different target substances, thereby enhancing the gas-sensing performance of the carrier material.

[0003] The application of MEMS micro-heating plates in the field of gas sensors has achieved a significant reduction in power consumption from hundreds of mW to tens of mW, and can achieve industrial-grade high consistency in fabrication. However, the integration of gas-sensitive films into MEMS micro-heating plates still relies on independent operation of individual devices. This results in process precision issues such as uneven thickness, excessively large coating areas, and inability to uniformly modify noble metals. These issues can lead to signal crosstalk between the sensor electrodes, and the noble metals cannot exert the same catalytic effect on each device, ultimately affecting the consistency and stability of the sensor. Furthermore, in existing technologies, the integration of gas-sensitive films into MEMS micro-heating plates involves only high-temperature sintering and annealing of the MEMS gas sensor by introducing air, which fails to fully utilize the catalytic properties of noble metals, resulting in poor sensitivity of the final MEMS gas sensor. Summary of the Invention

[0004] To address the shortcomings and improvement needs of existing technologies, this invention provides a noble metal-modified wafer-level MEMS gas sensor, its fabrication method, and its application, aiming to simultaneously improve the sensitivity, consistency, and stability of MEMS gas sensors.

[0005] To achieve the above objectives, according to one aspect of the present invention, a method for fabricating a noble metal-modified wafer-level MEMS gas sensor is provided, comprising the following steps:

[0006] Step S1: Fabricate a MEMS micro-heating plate array on a silicon wafer substrate;

[0007] Step S2: Prepare a gas-sensitive thin film in the central region of each sensing unit of the MEMS micro-heating plate array;

[0008] Step S3: Uniformly deposit noble metal on the surface of the gas-sensitive film to modify the gas-sensitive film and form a MEMS gas sensor array;

[0009] Step S4: Perform high-temperature sintering annealing of the MEMS gas sensor array using an air-hydrogen-air cycle;

[0010] Step S5: Divide and package the annealed MEMS gas sensor array to form a single MEMS gas sensor.

[0011] Furthermore, in step S2, a mask technique is used in the process of preparing the gas-sensitive thin film, including aligning the central region of each sensing unit of the MEMS micro-heating plate array with the cutout region of the mask.

[0012] Further, in step S4, the high-temperature sintering is carried out in a sintering furnace or under pressure in-situ annealing, with a temperature of 400-800°C and a duration of 1-4 hours.

[0013] Furthermore, in step S3, the atomic percentage of the noble metal is 0.4%-8.6%.

[0014] Furthermore, the atomic percentage of the precious metal is 5.5%.

[0015] Furthermore, noble metals are uniformly deposited on the surface of the gas-sensitive thin film using atomic layer deposition.

[0016] The gas-sensitive thin film is prepared using thin film preparation techniques, including sputtering, evaporation, or deposition.

[0017] Furthermore, in step S1, the size of the silicon wafer is 1 to 12 inches.

[0018] Furthermore, in step S2, the gas-sensitive thin film includes semiconductor metal oxides such as zinc oxide, tin oxide, copper oxide, tungsten oxide, or indium oxide.

[0019] According to a second aspect of the present invention, a noble metal-modified wafer-level MEMS gas sensor is provided, wherein the MEMS gas sensor is prepared by the preparation method described in any one of the first aspects.

[0020] According to a third aspect of the present invention, an application of a noble metal-modified wafer-level MEMS gas sensor is provided, which applies the gas sensor described in the second aspect to hydrogen detection.

[0021] In summary, the above-described technical solutions conceived in this invention can achieve the following beneficial effects:

[0022] (1) The method for fabricating a wafer-level MEMS gas sensor with noble metal modification provided by the present invention is based on the fabrication of a MEMS micro-heating plate array on the entire wafer substrate. A gas-sensitive thin film is fabricated in the central region of each sensing unit of the MEMS micro-heating plate array. After appropriate noble metal modification, a wafer-level fabrication of a highly sensitive gas-tight thin film is achieved by an air-hydrogen-air cyclic annealing method. The experimental results also fully demonstrate the significant effect of the annealing method designed in the present invention. Furthermore, the present invention adopts the method of first fabricating a gas-sensitive thin film on the MEMS micro-heating plate array wafer, and then dicing and packaging it after annealing to form a single MEMS gas sensor. Compared with the prior art method of first dicing the MEMS micro-heating plate array and then fabricating the gas-sensitive thin film and packaging it, the method of the present invention belongs to wafer-level fabrication. The consistency of the single MEMS gas sensor formed is better, and the transfer is simpler and the cost is lower.

[0023] (2) Furthermore, a mask technique was employed to achieve patterned and uniform deposition of the gas-sensitive thin film, ensuring that the thin film material only functions in the central region of each sensing unit. This avoids the electrical crosstalk problem between the test and heating electrodes present in traditional thin film transfer methods, and also eliminates the impact of large-area gas-sensitive film coverage on subsequent sensor packaging and welding. This guarantees the consistency of film thickness and resistance between sensors and the consistency of MEMS gas sensors. Simultaneously, it facilitates the standardized fabrication of semiconductor MEMS gas sensors, significantly improving the production efficiency and yield of MEMS gas sensors.

[0024] (3) Furthermore, under the modification of a certain amount of precious metal, the high efficiency catalytic properties of the precious metal modification on the gas-sensing performance can be fully utilized, and the experimental results can further corroborate this conclusion.

[0025] (4) The application of a noble metal-modified wafer-level MEMS gas sensor provided by the present invention is to use a noble metal-modified gas-sensitive thin film gas sensor as a semiconductor gas sensor for hydrogen detection. The test results show that the sensor of the present invention has excellent gas-sensing performance such as a low detection limit of ppb level for hydrogen and a wide test range spanning 3 orders of magnitude.

[0026] In summary, the preparation method of the present invention is a wafer-level patterning preparation method for gas-sensitive thin films, which can solve the technical problems of uneven thickness, uncontrollable coating area, and inability to uniformly modify noble metals in gas-sensitive thin films prepared by existing technologies, and can realize the mass industrial preparation of MEMS gas sensors. Attached Figure Description

[0027] Figure 1 This is a flowchart illustrating the fabrication process of a noble metal-modified wafer-level MEMS gas sensor provided by the present invention.

[0028] Figure 2This is a schematic diagram showing the alignment of the central region of the sensing unit and the hollowed-out region of the mask provided by the present invention.

[0029] Figure 3 This invention provides a performance comparison of MEMS gas sensors prepared by air-hydrogen-air annealing and those prepared by air annealing alone, as provided in the embodiments of the present invention. Figure 3 (a) in the figure represents a performance comparison of MEMS gas sensors prepared by the two annealing methods at different concentrations of the gas to be measured. Figure 3 (b) in the figure represents a performance comparison of MEMS gas sensors prepared by two annealing methods at different operating temperatures.

[0030] Figure 4 This invention provides a performance comparison of different atomic percentages in its embodiments, wherein... Figure 4 In the figure (a), the performance of the sensor changes under different test gas concentrations when the gas-sensitive film is modified with different atomic percentages of noble metals. Figure 4 (b) in the figure represents the performance comparison of the gas-sensitive film modified with different atomic percentages of noble metals at different sensor operating temperatures.

[0031] Figure 5 The SEM, AFM, and HADDF-STEM characterization images provided in Embodiment 1 of the present invention are shown below. Figure 5 In the image, (a) represents a SEM image showing the local deposition patterning effect of the gas-sensitive thin film. Figure 5 (b) in the image represents the SEM image of the cross-sectional morphology of the gas-sensitive thin film; Figure 5 (c) in the figure represents the AFM characterization of the thin film surface roughness; Figure 5 In the figure, (d) represents the HADDF-STEM characterization of the gas-sensitive thin film cross section, and (e) and (f) represent the elemental distribution characterization of Sn and Pd elements, respectively.

[0032] Figure 6 The graph shows the hydrogen sensing performance test of the sensor provided in Embodiment 1 of the present invention. Figure 6 In the figure, (a)-(d) represent the test results of the sensor's dynamic sensing behavior, consistency, repeatability and resolution, respectively. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0034] like Figure 1 As shown, the present invention provides a method for fabricating a noble metal-modified wafer-level MEMS gas sensor, comprising the following steps:

[0035] Step S1: Fabricate a MEMS micro-heating plate array on a silicon wafer substrate;

[0036] Step S2: Prepare a gas-sensitive thin film in the central region of each sensing unit on the MEMS micro-heating plate array using thin film fabrication technology;

[0037] Step S3: Uniformly deposit noble metal on the surface of the prepared gas-sensitive film to modify the gas-sensitive film and form a MEMS gas sensor array;

[0038] Step S4: Perform high-temperature sintering annealing of the formed MEMS gas sensor array using an air-hydrogen-air cycle;

[0039] Step S5: Divide and package the annealed MEMS gas sensor array to form a single MEMS gas sensor.

[0040] Preferably, in step S2, during the preparation of the gas-sensitive thin film, a mask technique is also employed, specifically including:

[0041] Align the central region of each sensing unit on the MEMS micro-heating plate array with the cutout region of the mask; the cutout region of the mask perfectly matches the area to be covered by the gas-sensitive film. Align the two, and the alignment error between the central region of the sensing unit and the cutout region of the mask is 0 to 300 μm.

[0042] Preferably, the mask thickness is 0.05–3 mm, and the mask material is metal, plastic, or resin.

[0043] Specifically, in step S1, the silicon wafer size of the MEMS micro heating plate array is 1 to 12 inches, and the wafer includes heating electrodes and test electrodes.

[0044] Specifically, in step S2, the central region of each sensing unit can be any shape such as rectangle or circle, and the central region of each sensing unit covers the channel of the test electrode.

[0045] Preferably, the gas-sensitive thin film includes materials with gas-sensitive properties such as semiconductor metal oxides like zinc oxide, tin oxide, copper oxide, tungsten oxide, or indium oxide. The film thickness ranges from 5 nm to 1000 nm.

[0046] Thin film preparation techniques include sputtering, evaporation, or deposition.

[0047] Specifically, in step S3, the noble metal-modified gas-sensitive thin film is prepared by atomic layer deposition.

[0048] The atomic percentage of noble metal deposited on the surface of the prepared gas-sensitive film is 0.4%-8.6%; preferably, the atomic percentage of noble metal is 5.5%, at which the catalytic properties of the gas-sensitive film modified with noble metal are the best.

[0049] Preferred catalysts include precious metals such as palladium and platinum.

[0050] In step S4, the high-temperature sintering method can be sintering furnace or pressurized in-situ annealing, with a temperature of 400-800℃ and a duration of 1-4h.

[0051] The technical solution and corresponding technical effects of the present invention will be further explained below with specific embodiments.

[0052] Example 1

[0053] In this embodiment, the gas-sensitive film is a tin oxide film, and the noble metal is palladium. The MEMS gas sensor is prepared using the above-described preparation method.

[0054] In step S2, magnetron sputtering is used to sputter a tin oxide film in the central region of the sensing unit. The target material is a 3-inch diameter 99.99% high-purity Sn target. The 950nm high-uniformity SnO2 film is sputtered under the following conditions: chamber vacuum <5×10-4Pa, DC power 100W, pressure 1.0Pa, gas Ar:O2 = 24:8sccm, and room temperature. Other areas are shielded by a mask and are not covered by the film.

[0055] In step S3, palladium with an atomic percentage of 5.5% is uniformly deposited on the surface of the aforementioned tin oxide film for 30 cycles using atomic layer deposition (ALD). During deposition, the reaction chamber temperature is 200°C, the pipeline heating temperature is 150°C, and the carrier gas flow rate is N2 50 sccm. During the reaction, N2, Pd(hafc)2, and tBuNHNH2 are sequentially introduced with pulse times of 10 ms, 1000 ms, and 200 ms, respectively. The chamber is purged with high-purity N2 for 25 s between precursor source switching.

[0056] In step S4, the MEMS gas sensor array with palladium-modified tin oxide thin film prepared above is subjected to overall air-hydrogen-air high-temperature sintering; the air annealing conditions are 5℃ / s heating to 400℃, holding for 2.5h and then naturally cooling down, and the hydrogen annealing conditions are 20℃ / min heating to 250℃, holding for 2.5h and then naturally cooling down.

[0057] The MEMS gas sensor prepared under the above parameters was tested. 10 ppm of test gas H2 was introduced, the sensor operating temperature was 110℃, and the sensitivity of the prepared MEMS gas sensor was measured to be 1.16.

[0058] Example 2

[0059] Unlike Example 1, the concentration of the gas H2 to be tested was 50 ppm, and the sensitivity of the prepared MEMS gas sensor is shown in Table 1.

[0060] Example 3

[0061] Unlike Example 1, the concentration of the gas H2 to be tested was 100 ppm, and the sensitivity of the prepared MEMS gas sensor is shown in Table 1.

[0062] Examples 4-6

[0063] Unlike Example 1, the concentration of the gas H2 to be tested was 20 ppm, and the sensor operating temperatures were 20℃, 110℃, and 220℃, respectively. The sensitivity of the prepared MEMS gas sensor is shown in Table 1.

[0064] Comparative Examples 1-3

[0065] Unlike Example 1, the concentrations of the gas H2 to be tested were 10ppm, 50ppm, and 100ppm, and the annealing method was air annealing, that is, the atmosphere introduced during annealing was only air. The sensitivity of the prepared MEMS gas sensor is shown in Table 1.

[0066] Comparative Examples 4-6

[0067] Unlike Example 1, the concentration of the gas H2 to be tested was 20 ppm, the annealing method was air annealing, and the sensor operating temperatures were 20℃, 110℃, and 220℃, respectively. The sensitivity of the prepared MEMS gas sensor is shown in Table 1.

[0068] As can be seen from Examples 1-3 and Comparative Examples 1-3 above, under different concentrations of the gas to be measured, the sensitivity of the MEMS gas sensor prepared by the air-hydrogen-air cyclic annealing method is higher than that of the MEMS gas sensor prepared by the air annealing method. Specific test results are shown in the figure below. Figure 3 As shown in (a) in the figure.

[0069] As can be seen from Examples 4-6 and Comparative Examples 4-6 above, at different operating temperatures, the sensitivity of the MEMS gas sensor prepared by the air-hydrogen-air cyclic annealing method is higher than that of the MEMS gas sensor prepared by the air annealing method. Specific test results are shown in the figure below. Figure 3 As shown in (b) of the diagram.

[0070] Table 1. Performance comparison of MEMS gas sensors prepared under different annealing methods

[0071]

[0072] In Table 1, annealing method 1 indicates that the air-hydrogen-air cycle annealing method is used, and annealing method 2 indicates that air annealing is used.

[0073] Examples 7-10

[0074] Unlike Example 1, the percentage content of noble metal atoms was 0%, 0.4%, 5.5%, and 8.6%, respectively. The sensitivity of the prepared MEMS gas sensor is shown in Table 2.

[0075] Examples 11-14

[0076] Unlike Example 1, the percentage content of noble metal atoms was 0%, 0.4%, 5.5%, and 8.6%, respectively, and the concentration of the gas H2 to be tested was 50 ppm. The sensitivity of the prepared MEMS gas sensor is shown in Table 2.

[0077] Examples 15-18

[0078] Unlike Example 1, the percentage content of noble metal atoms was 0%, 0.4%, 5.5%, and 8.6%, respectively, and the concentration of the gas H2 to be tested was 100 ppm. The sensitivity of the prepared MEMS gas sensor is shown in Table 2.

[0079] Examples 19-22

[0080] Unlike Example 1, the percentage content of noble metal atoms was 0%, 0.4%, 5.5%, and 8.6%, the concentration of the gas H2 to be tested was 20 ppm, and the sensor operating temperature was 20°C. The sensitivity of the prepared MEMS gas sensor is shown in Table 2.

[0081] Examples 23-26

[0082] Unlike Example 1, the percentage content of noble metal atoms was 0%, 0.4%, 5.5%, and 8.6%, the concentration of the gas H2 to be tested was 20 ppm, and the sensor operating temperature was 110°C. The sensitivity of the prepared MEMS gas sensor is shown in Table 2.

[0083] Examples 27-20

[0084] Unlike Example 1, the percentage content of noble metal atoms was 0%, 0.4%, 5.5%, and 8.6%, the concentration of the gas H2 to be tested was 20 ppm, and the sensor operating temperature was 220°C. The sensitivity of the prepared MEMS gas sensor is shown in Table 2.

[0085] As can be seen from Examples 7-18 above, modifying the gas-sensitive film with noble metals of different atomic percentages resulted in variations in sensor sensitivity under different test gas concentrations. The modification effect was best when the atomic percentage of the noble metal was 5.5%, with the sensor exhibiting the highest sensitivity at all gas concentrations. Specific test results are shown in the figure below. Figure 4 As shown in (a) in the figure.

[0086] As can be seen from Examples 19-30 above, modifying the gas-sensitive film with noble metals of different atomic percentages resulted in variations in sensor sensitivity at different sensor operating temperatures. The modification effect was best when the atomic percentage of the noble metal was 5.5%, with the sensor exhibiting the highest sensitivity at all temperatures. Specific test results are shown in the figures below. Figure 4 As shown in (b) of the diagram.

[0087] Table 2 Comparison of sensor performance obtained under noble metal modification with different atomic percentages

[0088]

[0089] Furthermore, the MEMS gas sensor prepared in Example 1 was subjected to the following morphology and performance tests:

[0090] The local deposition effect of tin oxide thin films was characterized using field emission scanning electron microscopy (SEM), such as... Figure 5 As shown in (a), the resulting array is a rectangular block array with clear edges and a shape consistent with the mask openings. The masked areas retain the original contrast color of the substrate, indicating that mask technology was used to achieve patterned and uniform deposition of the gas-sensitive thin film. The thin film material only functions in the central region of each sensing unit, avoiding the electrical crosstalk problem between the test and heating electrodes present in traditional thin film transfer methods, and also eliminating the impact of large-area gas-sensitive film coverage on subsequent sensor packaging and welding. Figure 5 As shown in (b), the surface of the deposited gas-sensitive film is very smooth, ensuring the consistency of resistance and performance between sensors;

[0091] Atomic force microscopy (AFM) was used to test surface roughness and obtain morphological and structural information, such as... Figure 5As shown in (c), the film is composed of uniformly distributed small particles and has a small surface roughness within ±10nm, indicating that the process flow of the present invention has good process consistency.

[0092] The basic composition and distribution of the samples were assessed using high-angle annular dark-field imaging-scanning transmission electron microscopy (HAADF-STEM) and elemental distribution maps, such as... Figure 5 As shown in (d)-(f), it can be clearly observed that the sample is composed of three elements: Sn, O and Pd. The palladium nanoparticles are modified on the film surface in a uniformly dispersed state, without complete coverage and with a thickness of <10nm. The boundary between the two is very clear, indicating that under the modification of a specific amount of noble metal, the noble metal particles are fully exposed, which can give full play to the efficient catalytic properties of noble metal modification on gas sensing performance.

[0093] The hydrogen sensing performance of the MEMS gas sensor with palladium-modified tin oxide thin film prepared in Example 1 of this invention was tested using a static gas sensing test system.

[0094] like Figure 6 As shown in (a), the figure illustrates the dynamic sensing behavior of the sensor for H2 concentrations ranging from 0.5 to 500 ppm at 150 °C. With increasing H2 concentration, the resistance and sensitivity gradually change, exhibiting a good linear relationship. At all concentrations, even at 500 ppm, the resistance recovers and stabilizes rapidly. For the lower limit of the measurement range, even at H2 concentrations as low as 0.5 ppm, the resistance and sensitivity still show significant changes. Compared to H2 sensors disclosed in the prior art, the sensor prepared by the method of this invention has a lower detection limit and a wider detection range, reaching three orders of magnitude.

[0095] like Figure 6 As shown in (b) of the figure, the response of four sensors from different locations on the wafer is displayed under the same operating temperature (150°C) and the same H2 concentration (0.5–500 ppm). It can be seen from the figure that the responses of the four sensors are consistent and exhibit good linearity, indicating that the wafer-level fabrication method of this invention produces a single MEMS gas sensor with better consistency.

[0096] like Figure 6 As shown in (c), the figure illustrates the repeatability test of the sensor at 150°C with 20 ppm H2 gas. The sensor resistance after H2 introduction is between 1020 Ω and 1029 Ω, with fluctuations much smaller than the baseline value, demonstrating that the sensor prepared by the method of this invention exhibits good repeatability.

[0097] like Figure 6As shown in (d), the figure illustrates five consecutive injections of a low concentration of H2 (2 ppm) to evaluate the resolution of the sensor prepared according to this invention. The figure shows that the resistance changes further with each H2 injection and remains stable after a specific response time until the gas test chamber is opened. This result demonstrates that the sensor prepared by the method of this invention exhibits good reproducibility and resolution for H2.

[0098] The noble metal-modified wafer-level MEMS gas sensor fabrication method provided by this invention employs mask technology to achieve patterned and uniform deposition of the gas-sensitive thin film. This ensures that the thin film material only functions in the central region of each sensing unit, avoiding the electrical crosstalk problem between the test electrode and the heating electrode present in traditional thin film transfer methods. It also eliminates the impact of large-area gas-sensitive film coverage on subsequent sensor packaging and welding, ensuring the consistency of film thickness and resistance between sensors and the consistency of MEMS gas sensors. Furthermore, this method first fabricates the gas-sensitive thin film on the MEMS micro-heating plate array wafer, and after annealing, it is diced and packaged to form a single MEMS gas sensor. Compared to the existing technology of dicing the MEMS micro-heating plate array before fabricating the gas-sensitive thin film and packaging, this invention's method is a wafer-level fabrication, resulting in better consistency of the formed single MEMS gas sensors. Subsequent packaging and testing processes can be performed in batches, significantly reducing operational difficulty and cost. This facilitates the standardized fabrication of semiconductor MEMS gas sensors and can significantly improve the production efficiency and yield of MEMS gas sensors.

[0099] After depositing a gas-sensitive thin film on a MEMS micro-heating plate array wafer, a wafer-level fabrication of a highly sensitive gas-sensitive thin film was achieved through an air-hydrogen-air cyclic annealing method. The experimental results also fully demonstrate the significant effect of the annealing method designed in this invention.

[0100] With the addition of a specific amount of precious metals, the highly efficient catalytic properties of the precious metal modification on the gas-sensing performance can be fully utilized, and the experimental results can further corroborate this conclusion.

[0101] The present invention provides an application of a noble metal-modified wafer-level MEMS gas sensor, which uses a noble metal-modified gas-sensitive thin-film gas sensor as a semiconductor gas sensor for hydrogen detection. Test results show that the sensor of the present invention has excellent gas-sensing performance, such as a low detection limit of ppb for hydrogen and a wide test range spanning three orders of magnitude.

[0102] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a noble metal modified wafer level MEMS gas sensor, the method comprising: providing a wafer level MEMS gas sensor; and depositing a noble metal on the wafer level MEMS gas sensor. Includes the following steps: Step S1: Fabricate a MEMS micro-heating plate array on a silicon wafer substrate; Step S2: Prepare a gas-sensitive thin film in the central region of each sensing unit of the MEMS micro-heating plate array; Step S3: A noble metal is uniformly deposited on the surface of the gas-sensitive film using atomic layer deposition to modify the gas-sensitive film and form a MEMS gas sensor array. Step S4: Perform air-hydrogen-air cycle high-temperature sintering annealing on the MEMS gas sensor array; in the air-hydrogen-air cycle high-temperature sintering annealing, the air annealing conditions are to heat up to 400℃ at 5℃ / s, hold for 2.5h and then cool down naturally, and the hydrogen annealing conditions are to heat up to 250℃ at 20℃ / min, hold for 2.5h and then cool down naturally. Step S5: Divide and package the annealed MEMS gas sensor array to form a single MEMS gas sensor.

2. The preparation method according to claim 1, characterized in that, In step S2, a mask technique is used in the process of preparing the gas-sensitive thin film, including aligning the central region of each sensing unit of the MEMS micro-heating plate array with the cutout region of the mask.

3. The preparation method according to claim 1, characterized in that, Step S4, the high-temperature sintering is a sintering furnace or pressurized in-situ annealing.

4. The preparation method according to claim 1, characterized in that, In step S3, the atomic percentage of the noble metal is 0.4%-8.6%.

5. The preparation method according to claim 4, characterized in that, The atomic percentage of the precious metal is 5.5%.

6. The preparation method according to claim 1, characterized in that, The gas-sensitive thin film is prepared using thin film preparation techniques, including sputtering, evaporation, or deposition.

7. The preparation method according to claim 1, characterized in that, In step S1, the size of the silicon wafer is 1 to 12 inches.

8. The preparation method according to claim 1, characterized in that, In step S2, the gas-sensitive thin film includes semiconductor metal oxides such as zinc oxide, tin oxide, copper oxide, tungsten oxide, or indium oxide.

9. A noble metal-modified wafer-level MEMS gas sensor, characterized in that, The MEMS gas sensor is prepared by the preparation method described in any one of claims 1-8.

10. An application of a noble metal-modified wafer-level MEMS gas sensor, characterized in that, The gas sensor described in claim 9 is applied to hydrogen detection.

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