Gas sensor suitable for high humidity environment detection and preparation process thereof

Abstract

The application discloses a kind of gas sensor suitable for high humidity environment detection and preparation process thereof, belong to sensor technical field.The gas sensor includes: silicon substrate layer and silicon dioxide structure layer, the silicon dioxide structure layer is set above the silicon substrate layer;The silicon dioxide structure layer includes the PAD region of being set at both ends and the gas sensor region of being set in the center;The gas sensor region includes heating resistance, sensing electrode, via metal column and gas sensitive material, both sides are fixed, and the whole is suspended above cavity;The via metal column is densely distributed above sensing electrode, so that gas sensor has super-hydrophobic property.The application designs metal layer and metal via pattern, makes a large number of via metal column be distributed above sensing electrode, so as to have super-hydrophobic property, can reduce the sensitivity degree of gas sensor to environmental humidity change when working, integrated and continuous process greatly reduces the cost of sensor.

Description

Technical Field

[0001] This invention relates to a gas sensor suitable for detecting high humidity environments and its manufacturing process, belonging to the field of sensors. Background Technology

[0002] With the further development of technology, the human world is making great strides into the era of the Internet of Things (IoT). In the IoT era, intelligent sensors are a crucial foundation for realizing the interconnection of everything, and gas sensors are one of the most important types of sensors. As a key component of intelligent detection systems, gas sensors have attracted attention due to their wide range of applications in fields such as smart healthcare, IoT, environmental science, the automotive industry, and the military. For example, by detecting volatile organic compounds (VOCs) naturally emitted by the human body, painless, real-time, and convenient diagnosis of related diseases can be achieved, which plays a positive role in building personal intelligent medical systems. In terms of environmental protection, by establishing intelligent gas sensing systems, real-time monitoring of polluted gases or other toxic and harmful gases can be achieved, greatly alleviating the pressure of large-scale air quality monitoring. In high-end manufacturing or the military field, the requirements for the gas environment are even more stringent. Extremely small amounts of certain gases can have a significant impact on the manufacturing of precision parts, and these environments are often characterized by high temperature, high pressure, and high humidity. This necessitates intelligent gas sensors that can perform well and stably in extreme environments such as high temperature, high pressure, and high humidity.

[0003] In the era of the Internet of Things (IoT), high price is a major factor limiting the widespread application of gas sensors. Most gas sensors on the market today cost well over $10 and require embedding in specialized equipment to function properly, pushing the price above $500. The current market size for gas sensors is estimated at around $500 million, growing at a rate of 10% annually. However, recent market growth has been driven by the development of miniature solid-state gas sensors (such as tin oxide resistive gas sensors) to reduce unit costs. When gas sensors (including readout interfaces) fall below $10, they can penetrate various industrial markets; when they fall below $1, they can penetrate even more markets. Once the unit cost is below $1, gas sensors can be embedded in laptops, smart homes, mobile phones, and even watches. Therefore, expanding the market size of gas sensors requires a significant reduction in unit cost, which is clearly impossible through conventional manufacturing processes. However, CMOS-MEMS manufacturing processes offer advantages such as low cost, mass production capability, high accuracy, high integration, and good compatibility with CMOS circuits. Therefore, researching CMOS-MEMS smart gas sensors is a feasible approach to addressing the problems of high manufacturing costs and poor performance in traditional sensors.

[0004] Besides the high manufacturing cost, most gas sensors are prone to failure in high humidity environments. This is mainly because when the relative humidity exceeds 80% or even 100%, a continuous, large-area water film forms on the sensor's sensing element. First, this water film drastically reduces the contact sites between the gas-sensitive material and gas molecules, significantly impairing the sensor's detection range, detection limit, and sensitivity, and in severe cases, directly causing sensor failure. Second, some gas-sensitive materials are water-soluble, and the presence of a water film may directly dissolve or damage these materials, impairing sensor performance or causing them to fail. Furthermore, the water film may react directly with the gas-sensitive material, causing "false responses" and resulting in inaccurate measurements. Finally, a continuous, large-area water film slows down water vapor evaporation, severely affecting the sensor's response / recovery speed. Therefore, by designing the sensing element surface with superhydrophobic properties, the formation of a continuous, large-area water film can be avoided, effectively solving the above problems.

[0005] In conclusion, developing a gas sensor suitable for high humidity environments is an effective way to address the issues of high unit cost and unstable operation of smart sensors in high humidity environments. Summary of the Invention

[0006] The main objective of this invention is to provide a gas sensor suitable for high humidity environment detection and its fabrication process. This invention overcomes the shortcomings of existing technologies to ensure that the gas sensor can meet the needs of smart healthcare, air quality monitoring, and hazardous gas leak detection in extreme high humidity environments. The sensor utilizes standard CMOS technology for its design, achieving superhydrophobic properties on the sensor surface. This ensures that the gas sensor is unaffected by ambient humidity when detecting specific gases, thus significantly improving the accuracy and applicability of the gas sensor. Simultaneously, the Post-CMOS process has the advantage of eliminating the need for mask operations, effectively reducing the complexity of post-processing and greatly improving the efficiency of the entire Post-CMOS post-processing process.

[0007] The objective of this invention is achieved through the following technical solution.

[0008] A gas sensor suitable for high humidity environment detection includes a silicon substrate layer (1) and a silicon dioxide structure layer (2), wherein the silicon dioxide structure layer (2) is disposed above the silicon substrate layer (1); the silicon dioxide structure layer (2) includes PAD regions (7) disposed at both ends and a gas sensor region disposed in the center; in the PAD regions, silicon dioxide material and metal material are arranged in an overlapping manner, and metal vias penetrate from the first metal layer to the fifth metal layer; the gas sensor region includes a heating resistor (3), a sensing electrode (4), a via metal pillar (5), and The gas-sensitive material (6) is fixed on both sides and suspended above the cavity (8); the heating resistor (3) is distributed on the poly layer and patterned accordingly; the sensing electrode (4) is distributed on the first metal layer, and the electrode pattern is interdigitated capacitance or serpentine resistance; the via metal pillars (5) are densely distributed above the sensing electrode, so that the gas sensor has superhydrophobic properties; the gas-sensitive material (6) can be selected according to specific needs. Commonly used gas-sensitive materials mainly include metal oxides, polymers, and carbon nanomaterials such as graphene oxide and carbon nanotubes.

[0009] A method for fabricating a gas sensor suitable for high humidity environment detection, employing a mask-free Post-CMOS method, includes the following steps:

[0010] Step 1: Design the CMOS die using a 0.18um 1P6M process. Design a reasonable metal layer pattern and metal vias in the PAD area, filling the space between the sixth and fifth metal layers with silicon dioxide material. This forms a natural mask for the PAD area during metal etching, protecting its structure. Design a reasonable polysilicon layer pattern in the gas sensor area to form the heating resistor of the gas sensor. Design reasonable first and third metal layer patterns and the metal vias between them, so that a large number of via metal pillars are densely distributed on the sensing electrode, giving the gas sensor superhydrophobic properties and preventing it from being affected by ambient humidity during gas detection. At the same time, the third metal layer serves as a mask for subsequent processes, protecting the sensing electrode without a mask.

[0011] Step 2: The CMOS die obtained in Step 1 is etched with silicon dioxide to remove excess silicon dioxide and form trenches. The sixth and third metal layers mentioned above serve as masks for the PAD region and the gas sensor region, respectively. Then, metal etching is performed to remove the sixth and third metal layers that serve as masks. Silicon dioxide etching is then performed to expose the via metal pillars, forming a superhydrophobic structure on the surface of the sensing electrode. At the same time, the PAD is exposed to facilitate connection with the peripheral circuit. Meanwhile, the first metal layer serves as a mask for the heating resistor to protect its structure. Then, DRIE etching and XeF2 etching are performed to form a floating structure for the gas sensor, resulting in the prefabricated chip.

[0012] Step 3: Coat the prefabricated chip obtained in Step 2 with a specific gas-sensitive material according to actual needs to form a gas sensor suitable for high humidity environment detection.

[0013] A method for fabricating a gas sensor suitable for high humidity environment detection, employing a mask-free Post-CMOS method, includes the following steps:

[0014] Step 1: Design the CMOS die using a 0.18um 1P6M process. Design a reasonable metal layer pattern and metal vias in the PAD area, filling the space between the sixth and fifth metal layers with silicon dioxide material. This forms a natural mask for the PAD area during metal etching, protecting its structure. Design a reasonable polysilicon layer pattern in the gas sensor area to form the heating resistor of the gas sensor. Design reasonable first and third metal layer patterns and the metal vias between them, so that a large number of via metal pillars are densely distributed on the sensing electrode, giving the gas sensor superhydrophobic properties and preventing it from being affected by ambient humidity during gas detection. At the same time, the third metal layer serves as a mask for subsequent processes, protecting the sensing electrode without a mask.

[0015] Step 2: The CMOS die obtained in Step 1 is etched with silicon dioxide to remove excess silicon dioxide and form trenches. The sixth and third metal layers mentioned above serve as masks for the PAD region and the gas sensor region, respectively. Then, metal etching is performed to remove the sixth and third metal layers that serve as masks. Silicon dioxide etching is then performed again to expose the via metal pillars, forming a superhydrophobic structure on the surface of the sensing electrode. At the same time, the PAD is exposed to facilitate connection with the peripheral circuit. Meanwhile, the first metal layer serves as a mask for the heating resistor to protect its structure. Then, the sensor is flipped and anisotropic silicon etching is performed to form a suspended structure for the gas sensor, resulting in the prefabricated chip.

[0016] Step 3: Coat the prefabricated chip obtained in Step 2 with a specific gas-sensitive material according to actual needs to form a gas sensor suitable for high humidity environment detection.

[0017] Beneficial effects:

[0018] 1. This invention designs a metal layer and metal via pattern to distribute a large number of via metal pillars above the sensing electrode, thereby achieving superhydrophobic properties. This reduces the sensitivity of the gas sensor to changes in ambient humidity during operation, greatly improving sensing accuracy and applicability.

[0019] 2. This invention utilizes CMOS technology to obtain CMOS bare dies through reasonable design, enabling the post-CMOS process to obtain an ideal sensor structure without a mask, which greatly reduces the process complexity and manufacturing cost of the sensor.

[0020] 3. The present invention designs a heating resistor below the sensing electrode, which can detect a variety of gases by adjusting the heating power, greatly expanding the application range of the sensor.

[0021] 4. The overall suspension of the sensing structure can greatly reduce the power consumption of the sensor.

[0022] 5. The integrated and continuous manufacturing process significantly reduces the cost of the sensor, which also exhibits excellent stability, high sensitivity, low heat dissipation, and fast response / recovery performance. Suitable for gas sensors in high humidity environments, this small, highly integrated sensor has the potential to serve as a miniature, multi-functional dedicated sensor. It effectively solves the problems of unstable and inaccurate detection results from current gas sensors under varying or high humidity conditions, as well as the high cost, significant heat dissipation, and relatively limited sensitivity and response speed of commercially available gas sensors. Furthermore, the manufacturing process is simple, facilitating large-scale production from an industrialization perspective. Attached image description:

[0023] Figure 1 This is a flowchart of the fabrication process of Scheme 1 of the present invention, which is suitable for detecting gas sensors in high humidity environments. In the figure, Figure a shows the designed CMOS die, Figure b shows the silicon dioxide etching of the CMOS die, Figure c shows the metal etching, Figure d shows the silicon dioxide etching to expose the PAD, sensing electrode and silicon substrate, Figure e shows the DRIE etching to form trenches on the silicon substrate, Figure f shows the XeF2 etching to release the suspended thin film, and Figure g shows the final coating of the device with gas-sensitive material to form the final gas sensor.

[0024] Figure 2 This is a flowchart of the fabrication process of Scheme 2 of the present invention, which is suitable for detecting gas sensors in high humidity environments. In the figure, Figure a shows the designed CMOS die, Figure b shows the silicon dioxide etching of the CMOS die, Figure c shows the metal etching, Figure d shows the silicon dioxide etching to expose the PAD, sensing electrode and silicon substrate, Figure e shows the back cavity etching to form trenches on the silicon substrate to suspend the sensor, and Figure f shows the coating of the device with gas-sensitive material to form the final gas sensor.

[0025] Figure 3 This is a cross-sectional schematic diagram of a gas sensor suitable for detecting high humidity environments according to the present invention.

[0026] Figure 4This is a three-dimensional structural schematic diagram of a gas sensor suitable for detecting high humidity environments according to the present invention.

[0027] Figure 5 This is a comparative schematic diagram of a gas sensor of the present invention suitable for high humidity environment detection and a conventional gas sensor in a high humidity environment. Figure a shows the results of the gas sensor of the present invention in a high humidity environment; Figure b shows the results of a conventional gas sensor in a high humidity environment.

[0028] Wherein, 1-silicon substrate layer; 2-silicon dioxide structural layer; 3-heating resistor; 4-sensing electrode; 5-via metal pillar; 6-gas-sensitive material; 7-PAD region schematic diagram. Detailed Implementation

[0029] To better illustrate the purpose and advantages of the present invention, the invention will be further described below in conjunction with the accompanying drawings and examples.

[0030] See Figures 2 to 4 As shown: This embodiment discloses a gas sensor suitable for high humidity environment detection, which includes a silicon substrate layer (1) and a silicon dioxide structure layer (2). The silicon dioxide structure layer (2) is disposed above the silicon substrate layer (1). The silicon dioxide structure layer (2) includes PAD regions (7) disposed at both ends and a gas sensor region disposed in the center. In the PAD region, silicon dioxide material and metal material are arranged in an overlapping manner, and the metal via penetrates from the first metal layer to the fifth metal layer. The gas sensor region includes a heating resistor (3), a sensing electrode (4), a via metal pillar (5) and a gas-sensitive material (6), which are fixed on both sides and are suspended above the cavity (8). The heating resistor (3) is distributed on the poly layer and patterned accordingly. The sensing electrode (4) is distributed on the first metal layer, and the electrode pattern is interdigitated capacitance or serpentine resistance. The via metal pillar (5) is densely distributed above the sensing electrode, thereby giving the gas sensor superhydrophobic properties.

[0031] The metal pillars are densely distributed on the sensing electrode, and the overall pattern is similar to that of the sensing electrode.

[0032] The cross-sectional area of ​​a single metal via column needs to be designed appropriately to ensure that the surface tension between the droplet and the via metal column is greater than the droplet's own weight. This ensures that the droplet will not contact the sensing electrode at the bottom, keeping the droplet in a Wenzel state. As a result, it has a large contact angle and low friction, thus achieving superhydrophobic properties and avoiding problems such as inaccurate gas detection results caused by excessive ambient humidity.

[0033] The spacing between the via pillars needs to be designed properly. To a certain extent, the denser the via pillars, the better the superhydrophobicity of the device. However, it is not always better to be denser. When a certain limit is exceeded, excessively dense via pillars can lead to spontaneous destruction of the device's superhydrophobicity. Therefore, the appropriate density should be selected based on the actual situation and the materials used during the design process.

[0034] Gas-sensitive materials (6) can be selected according to specific needs. Commonly used gas-sensitive materials mainly include metal oxides, polymers, and carbon nanomaterials such as graphene oxide and carbon nanotubes.

[0035] The substrate material is a silicon wafer.

[0036] The structural layer is made of silicon dioxide.

[0037] The heating resistor in the gas sensor is made of polycrystalline silicon.

[0038] The sensing electrode is made of aluminum.

[0039] The material of the via metal column is tungsten.

[0040] See Figure 1 and Figure 2 As shown: This invention also provides two methods for preparing gas sensors suitable for high humidity environment detection.

[0041] Figure 1 This is a flowchart illustrating the preparation process of Scheme 1 of the gas sensor applicable to high humidity environment detection in the embodiments of the present invention, including the following steps:

[0042] Step 1: Design the CMOS die using a 0.18um 1P6M process. Design a reasonable metal layer pattern and metal vias in the PAD area, filling the space between the sixth and fifth metal layers with silicon dioxide material. This forms a natural mask for the PAD area during metal etching, protecting its structure. Design a reasonable polysilicon layer pattern in the gas sensor area to form the heating resistor of the gas sensor. Design reasonable first and third metal layer patterns and the metal vias between them, so that a large number of via metal pillars are densely distributed on the sensing electrode, giving the gas sensor superhydrophobic properties and preventing it from being affected by ambient humidity during gas detection. At the same time, the third metal layer serves as a mask for subsequent processes, protecting the sensing electrode without a mask.

[0043] Step 2: The CMOS die obtained in Step 1 is etched with silicon dioxide to remove excess silicon dioxide and form trenches. The sixth and third metal layers mentioned above serve as masks for the PAD region and the gas sensor region, respectively. Then, metal etching is performed to remove the sixth and third metal layers that serve as masks. Silicon dioxide etching is then performed to expose the via metal pillars, forming a superhydrophobic structure on the surface of the sensing electrode. At the same time, the PAD is exposed to facilitate connection with the peripheral circuit. Meanwhile, the first metal layer serves as a mask for the heating resistor to protect its structure. Then, DRIE etching and XeF2 etching are performed to form a floating structure for the gas sensor, resulting in the prefabricated chip.

[0044] Step 3: Coat the prefabricated chip obtained in Step 2 with a specific gas-sensitive material according to actual needs to form a CMOS-MEMS superhydrophobic gas sensor that is insensitive to humidity.

[0045] Figure 2 This is a flowchart illustrating the fabrication process of Scheme 2 of the present invention, which is a superhydrophobic gas sensor insensitive to humidity, including the following steps:

[0046] Step 1: Design the CMOS die using a 0.18um 1P6M process. Design a reasonable metal layer pattern and metal vias in the PAD area, filling the space between the sixth and fifth metal layers with silicon dioxide material. This forms a natural mask for the PAD area during metal etching, protecting its structure. Design a reasonable polysilicon layer pattern in the gas sensor area to form the heating resistor of the gas sensor. Design reasonable first and third metal layer patterns and the metal vias between them, so that a large number of via metal pillars are densely distributed on the sensing electrode, giving the gas sensor superhydrophobic properties and preventing it from being affected by ambient humidity during gas detection. At the same time, the third metal layer serves as a mask for subsequent processes, protecting the sensing electrode without a mask.

[0047] Step 2: The CMOS die obtained in Step 1 is etched with silicon dioxide to remove excess silicon dioxide and form trenches. The sixth and third metal layers mentioned above serve as masks for the PAD region and the gas sensor region, respectively. Then, metal etching is performed to remove the sixth and third metal layers that serve as masks. Silicon dioxide etching is then performed again to expose the via metal pillars, forming a superhydrophobic structure on the surface of the sensing electrode. At the same time, the PAD is exposed to facilitate connection with the peripheral circuit. Meanwhile, the first metal layer serves as a mask for the heating resistor to protect its structure. Then, the sensor is flipped and anisotropic silicon etching is performed to form a suspended structure for the gas sensor, resulting in the prefabricated chip.

[0048] Step 3: Coat the prefabricated chip obtained in Step 2 with a specific gas-sensitive material according to actual needs to form a CMOS-MEMS superhydrophobic gas sensor that is insensitive to humidity.

[0049] This invention employs a 0.18µm 1P6M CMOS semiconductor process to form the required sensor structure on a silicon wafer in a single step. The structure includes a silicon substrate layer 1 and a silicon dioxide structural layer 2, with the silicon dioxide structural layer 2 positioned above the silicon substrate layer 1. The silicon dioxide structural layer 2 includes PAD regions 7 at both ends and a gas sensor region in the center. In the PAD regions, silicon dioxide and metal materials are interleaved, with metal vias penetrating from the first to the fifth metal layer. The gas sensor region includes a heating resistor 3, a sensing electrode 4, via metal pillars 5, and a gas-sensitive material 6, fixed on both sides and suspended above a cavity 8. The heating resistor 3 is distributed on a poly layer and patterned accordingly. The sensing electrode 4 is distributed on the first metal layer, with an interdigitated capacitive or serpentine resistive pattern. The via metal pillars 5 are densely distributed above the sensing electrode, giving the gas sensor superhydrophobic properties. The gas-sensitive material 6 can be selected according to specific needs; commonly used gas-sensitive materials include metal oxides, polymers, and carbon nanomaterials such as graphene oxide and carbon nanotubes.

[0050] The present invention provides a practical application of a gas sensor suitable for high humidity environment detection, which may include: attaching the sensor to a carrier, extending a lead wire from one end, connecting it to an external signal processing module, and detecting the type and content of gas in the environment.

[0051] In this invention, the resistance or capacitance value is related to the type or content of the gas, and the signal response is determined by the change in resistance or capacitance value.

[0052] This invention utilizes a 0.18µm 1P6M process to design a sensor structure in a single step, including a silicon substrate layer 1, a silicon dioxide structural layer 2, and various functional components contained within the silicon dioxide structural layer. Then, a mask-free post-CMOS process is used to obtain a humidity-insensitive CMOS-MEMS superhydrophobic gas sensor with a suspended structure. Unlike the structures of ordinary CMOS-MEMS gas sensors, this invention innovatively proposes a humidity-insensitive CMOS-MEMS superhydrophobic gas sensor structure. By designing metal layers and via metal pillar patterns, the surface roughness of the sensor is significantly improved after a simple and continuous post-processing process, giving it superhydrophobicity and thus achieving humidity insensitivity. Generally, achieving superhydrophobic properties in devices starts with materials, such as changing the material type or altering the material growth process parameters. This invention cleverly utilizes the characteristics of CMOS technology to achieve superhydrophobic properties on the sensor surface at the structural level. Furthermore, this invention achieves post-processing of the device without a mask through a rational design, resulting in a gas sensor with good surface morphology, stable structure, excellent performance, and suitability for high-humidity environment detection.

[0053] This invention provides a gas sensor suitable for high humidity environment detection. It achieves superhydrophobic properties on the sensor surface at the structural level and possesses advantages such as robustness, high sensitivity, good stability, fast response speed, low heat dissipation, high accuracy, small size, and good designability. Therefore, it has the potential to serve as a small, multi-functional dedicated sensor. It effectively solves the problems of unstable and inaccurate detection results of current gas sensors under drastic changes in environmental humidity or high humidity, as well as the high cost, large heat dissipation, and relatively limited sensitivity and response speed of commercially available gas sensors. Furthermore, this invention employs an integrated CMOS fabrication process and a mask-free post-processing technology, facilitating large-scale production from an industrialization perspective.

[0054] The above are merely preferred embodiments of this application and are not intended to limit this application. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of this application should be included within the scope of protection of this application. Other structures and principles are the same as those in the prior art and will not be described in detail here.

Claims

1. A method for preparing a gas sensor suitable for detecting high humidity environments, characterized in that: The Post-CMOS method, which requires no mask operation, includes the following steps: Step 1: Design the CMOS die using a 0.18um 1P6M process. Design a reasonable metal layer pattern and metal vias in the PAD area, filling the space between the sixth and fifth metal layers with silicon dioxide material. This forms a natural mask for the PAD area during metal etching, protecting its structure. Design a reasonable polysilicon layer pattern in the gas sensor area to form the heating resistor of the gas sensor. Design reasonable first and third metal layer patterns and the metal vias between them, so that a large number of via metal pillars are densely distributed on the sensing electrode, giving the gas sensor superhydrophobic properties and protecting it from the influence of ambient humidity during gas detection. At the same time, the third metal layer serves as a mask for subsequent processes, protecting the sensing electrode without a mask. Step 2: The CMOS die obtained in Step 1 is etched with silicon dioxide to remove excess silicon dioxide and form trenches. The sixth and third metal layers mentioned above serve as masks for the PAD region and the gas sensor region, respectively. Then, metal etching is performed to remove the sixth and third metal layers that serve as masks. Silicon dioxide etching is then performed to expose the via metal pillars, forming a superhydrophobic structure on the surface of the sensing electrode. At the same time, the PAD is exposed to facilitate connection with the peripheral circuit. Meanwhile, the first metal layer serves as a mask for the heating resistor to protect its structure. Then, DRIE etching and XeF2 etching are performed to form a floating structure for the gas sensor, resulting in the prefabricated chip. Step 3: Coat the prefabricated chip obtained in Step 2 with a specific gas-sensitive material according to actual needs to form a gas sensor suitable for high humidity environment detection.

2. A method for preparing a gas sensor suitable for detecting high humidity environments, characterized in that: The Post-CMOS method, which requires no mask operation, includes the following steps: Step 1: Design the CMOS die using a 0.18um 1P6M process. Design a reasonable metal layer pattern and metal vias in the PAD area, filling the space between the sixth and fifth metal layers with silicon dioxide material. This forms a natural mask for the PAD area during metal etching, protecting its structure. Design a reasonable polysilicon layer pattern in the gas sensor area to form the heating resistor of the gas sensor. Design reasonable first and third metal layer patterns and the metal vias between them, so that a large number of via metal pillars are densely distributed on the sensing electrode, giving the gas sensor superhydrophobic properties and protecting it from the influence of ambient humidity during gas detection. At the same time, the third metal layer serves as a mask for subsequent processes, protecting the sensing electrode without a mask. Step 2: The CMOS die obtained in Step 1 is etched with silicon dioxide to remove excess silicon dioxide and form trenches. The sixth and third metal layers mentioned above serve as masks for the PAD region and the gas sensor region, respectively. Then, metal etching is performed to remove the sixth and third metal layers that serve as masks. Silicon dioxide etching is then performed again to expose the via metal pillars, forming a superhydrophobic structure on the surface of the sensing electrode. At the same time, the PAD is exposed to facilitate connection with the external circuit. Meanwhile, the first metal layer serves as a mask for the heating resistor to protect its structure. Then the sensor is flipped over and silicon is etched anisotropically to form a suspended structure for the gas sensor, thus obtaining the prefabricated chip. Step 3: Coat the prefabricated chip obtained in Step 2 with a specific gas-sensitive material according to actual needs to form a gas sensor suitable for high humidity environment detection.

3. A gas sensor suitable for detecting high humidity environments, prepared using the method described in claim 1 or 2, characterized in that: The system includes a silicon substrate layer (1) and a silicon dioxide structure layer (2), with the silicon dioxide structure layer (2) disposed above the silicon substrate layer (1). The silicon dioxide structure layer (2) includes PAD regions (7) disposed at both ends and a gas sensor region disposed in the center. In the PAD regions, silicon dioxide material and metal material are arranged in an overlapping manner, with metal vias penetrating from the first metal layer to the fifth metal layer. The gas sensor region includes a heating resistor (3), a sensing electrode (4), via metal pillars (5), and a gas-sensitive material (6), which are fixed on both sides and suspended above the cavity (8). The heating resistor (3) is distributed on the poly layer and patterned accordingly. The sensing electrode (4) is distributed on the first metal layer, and the electrode pattern is interdigitated capacitive or serpentine resistive. The via metal pillars (5) are densely distributed above the sensing electrode, thereby giving the gas sensor superhydrophobic properties.

4. The gas sensor as described in claim 3, characterized in that: The gas-sensitive material (6) is a metal oxide, a polymer, or a carbon nanomaterial.

5. The gas sensor as described in claim 4, characterized in that: The carbon nanomaterial is graphene oxide or carbon nanotubes.

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