Gas sensor

Abstract

The invention discloses a gas sensor, comprising: a substrate provided with a mounting cavity; a first induction resistor is arranged in the first heating plate; the first heating plate and the second heating plate are arranged in the mounting cavity of the substrate in a spaced mode, and a second induction resistor is arranged in the second heating plate. According to the gas sensor disclosed by the invention, the first heating plate and the second heating plate are arranged on the substrate, the gas sensor is constructed into a double-temperature-control double-hot-plate structure, and the characteristic that the heat conductivity of refrigerant gas in a specific high-temperature interval is obviously higher than that of dry air, water vapor, CO2 and the like is fully utilized, so that interference caused by environmental change factors is reduced; the purposes of improving the sensitivity, the signal-to-noise ratio and the like of the device are achieved. Meanwhile, by utilizing the characteristic that the heat conductivity of water vapor in the same high-temperature interval is very close to that of dry air, humidity compensation is simplified and even omitted.

Description

Technical Field

[0001] The present invention relates to the technical field of sensor manufacturing, and more specifically, to a gas sensor. Background Art

[0002] In the existing MEMS (Micro-Electro-Mechanical System) thermal conduction gas sensor technology, the gap between the heater (resistor) and the temperature sensor and the surrounding substrate is the gas to be measured, and its thermal conductivity directly affects the heating power required to control the temperature. This is the basic principle for detecting gases with different thermal conductivities.

[0003] At present, one of the difficulties of the existing technology is that the temperature range of the gas to be measured spans a large range, such as from several hundred degrees Celsius near the heater to near the ambient temperature / room temperature near the substrate. For R290 refrigerant gas, etc., in the heat dissipation path from the heater to the substrate (including lateral / in-plane and longitudinal / out-of-plane), there is always a part of the path where the thermal conductivity of the refrigerant gas is higher than that of air (such as medium and high temperature areas), while the other part of the path is lower than that of air (medium and low temperature areas). The overall effect is that the difference between the effective thermal conductivity of the refrigerant gas and the air in the heat dissipation path is offset, resulting in reduced sensitivity.

[0004] The second technical difficulty is that for third and fourth generation refrigerants such as R290 and R32, the thermal conductivity is lower than that of air at room temperature and pressure, and is close to that of water vapor (18 / R290, 13 / R32, 18.7 / water vapor vs. 26.2 / air mW / mK at 300K 1ATM). Given the huge range of water vapor changes caused by humidity (the volume content of saturated water vapor at room temperature of 25+ / -5C can be as high as about 2.8-5.2%), it is also very difficult to compensate the humidity to the required detection accuracy (such as 1000ppm). Summary of the invention

[0005] One object of the present invention is to provide a new technical solution for a gas sensor, which can at least solve the problems of low sensitivity and difficulty in humidity compensation in the prior art.

[0006] The present invention provides a gas sensor, comprising: a substrate, on which a mounting cavity is provided; a first heating plate, in which a first induction resistor is provided; and a second heating plate, the first heating plate and the second heating plate are arranged in the mounting cavity of the substrate at a distance from each other, in which a second induction resistor is provided.

[0007] Optionally, in the thickness direction of the substrate, the spacing distance between the first heating plate and the second heating plate is 1-5 μm, and the distance between the second heating plate and the substrate is 1-5 μm.

[0008] Optionally, the number of the first sensing resistors in the first heating plate is one or more, and the number of the second sensing resistors in the second heating plate is one or more.

[0009] Optionally, a cross-sectional length of the first heating plate and the second heating plate is 100-200 μm.

[0010] Optionally, the first heating plate includes a first insulating layer, which is coated around the outer periphery of the first sensing resistor, and the second heating plate includes a second insulating layer, which is coated around the outer periphery of the second sensing resistor.

[0011] Optionally, the material of the first sensing resistor and the second sensing resistor are both one of polysilicon, non-polysilicon, metal or alloy.

[0012] Optionally, the thickness of the first sensing resistor and the second sensing resistor are both 0.1-1 μm.

[0013] Optionally, the first insulating layer and the second insulating layer are both made of a composite layer of silicon dioxide and silicon-rich silicon nitride, and have a thickness of 0.1-1 μm.

[0014] Optionally, the gas sensor further includes: a plurality of first beam arms and a plurality of second beam arms, wherein the plurality of first beam arms are spaced apart and distributed along the circumference of the first heating plate and respectively connect the first heating plate and the substrate, and the plurality of second beam arms are spaced apart and distributed along the circumference of the second heating plate and respectively connect the second heating plate and the substrate.

[0015] Optionally, a third inductive resistor is provided in the first beam arm, and a fourth inductive resistor is provided in the second beam arm.

[0016] The gas sensor of the present invention is constructed into a dual-temperature-controlled dual-heat-plate structure by arranging a first heating plate and a second heating plate on a substrate, making full use of the fact that the thermal conductivity of the refrigerant gas in a specific high-temperature range is significantly higher than that of dry air, water vapor, CO2, etc., so as to reduce the interference caused by these environmental change factors, thereby achieving the purpose of improving the device sensitivity, signal-to-noise ratio, and other performances. At the same time, by utilizing the fact that the thermal conductivity of water vapor in the same high-temperature range is very close to that of dry air, humidity compensation is simplified or even omitted.

[0017] Further features and advantages of the present invention will become apparent from the following detailed description of exemplary embodiments of the present invention with reference to the attached drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.

[0019] Figure 1 is a schematic structural diagram of a gas sensor according to an embodiment of the present invention;

[0020] Figure 2 is a cross-sectional view of a gas sensor according to an embodiment of the present invention;

[0021] Figure 3 is another cross-sectional view of a gas sensor according to an embodiment of the present invention.

[0022] Reference numerals:

[0023] Gas sensor 100;

[0024] Substrate 10; mounting cavity 11;

[0025] First heating plate 20; first induction resistor 21; first insulating layer 22;

[0026] A second heating plate 30; a second sensing resistor 31; a second insulating layer 32;

[0027] First beam arm 40; third sensing resistor 41; third insulating layer 42;

[0028] The second beam arm 50 ; the fourth sensing resistor 51 ; and the fourth insulating layer 52 . DETAILED DESCRIPTION

[0029] Various exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings. It should be noted that the relative arrangement of components and steps, numerical expressions and numerical values ​​set forth in these embodiments do not limit the scope of the present invention unless otherwise specifically stated.

[0030] The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way intended to limit the invention, its application, or uses.

[0031] Technologies, methods, and equipment known to ordinary technicians in the relevant art may not be discussed in detail, but where appropriate, the technologies, methods, and equipment should be considered as part of the specification.

[0032] In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not limiting. Therefore, other examples of the exemplary embodiments may have different values.

[0033] It should be noted that like reference numerals and letters refer to similar items in the following figures, and therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0034] In the specification and claims of the present invention, if the term "first" or "second" is involved, it may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "plurality" means two or more. In addition, "and / or" in the specification and claims means at least one of the connected objects, and the character " / " generally means that the related objects are in an "or" relationship.

[0035] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, which are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation to the present invention.

[0036] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installation", "connection" and "connection" involved should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0037] The gas sensor 100 according to the embodiment of the present invention is described in detail below with reference to the accompanying drawings.

[0038] like Figures 1 to 3 As shown, the gas sensor 100 according to the embodiment of the present invention includes a substrate 10 , a first heating plate 20 , and a second heating plate 30 .

[0039] Specifically, the substrate 10 is provided with a mounting cavity 11. The first heating plate 20 is provided with a first inductive resistor 21. The first heating plate 20 and the second heating plate 30 are spaced apart and arranged in the mounting cavity 11 of the substrate 10, and the second heating plate 30 is provided with a second inductive resistor 31.

[0040] In other words, if Figures 1 to 3As shown, the gas sensor 100 according to the embodiment of the present invention is mainly composed of a substrate 10, a first heating plate 20 and a second heating plate 30. Figure 2 and Figure 3 As shown, a mounting cavity 11 is provided on the substrate 10. A first inductive resistor 21 is provided in the first heating plate 20. The first inductive resistor 21 can be used for both heating and temperature measurement. The first heating plate 20 and the second heating plate 30 are arranged in the mounting cavity 11 of the substrate 10 at intervals, and the gas sensor 100 is constructed into a dual-temperature controlled dual-hot plate structure. A second inductive resistor 31 is provided in the second heating plate 30. The second inductive resistor 31 can be used for both heating and temperature measurement. The gap between the first heating plate 20, the second heating plate 30 and the substrate 10 is used to introduce the gas to be measured. By arranging the first heating plate 20 and the second heating plate 30 on the substrate 10, the gas sensor 100 is constructed into a dual-temperature controlled dual-hot plate structure, which can make full use of the characteristics that the thermal conductivity of the refrigerant gas in a specific high temperature range is significantly higher than that of dry air, water vapor, CO2, etc., so as to reduce the interference caused by these environmental change factors, and achieve the purpose of improving the device sensitivity, signal-to-noise ratio and other performance. At the same time, by utilizing the characteristics that the thermal conductivity of water vapor in the same high temperature range is very close to that of dry air, humidity compensation is simplified or even omitted.

[0041] It should be noted that most of the gas sensors 100 are sensitive to the environment (humidity, temperature, pressure), and are usually compensated by a multivariate calibration method based on a large amount of experimental data. Among them, the MEMS thermal conductivity gas sensor 100 has the characteristics of miniaturization, fast response, low cost and low power consumption, and has attracted much attention. It not only has an advantage in the detection field of conventional high thermal conductivity gases (such as H2, He), but also gradually enters the market in the leakage detection of some refrigerant gases (such as the fourth generation refrigerant R290, etc.). Of course, its performance such as sensitivity and anti-interference ability to environmental factors (such as humidity, temperature, pressure, etc.) need to be further improved. In particular, the thermal conductivity of some gases (such as the fourth generation refrigerant R290, etc.) is lower than that of air near room temperature, and only at high temperatures (such as above 300C) is it greater than air and more suitable for such principle detection. In the usual MEMS design, the refrigerant gas spans the range from high temperature to (substrate 10) room temperature, and the influence of average thermal conductivity leads to lower sensitivity. In addition, the thermal conductivity of water vapor is very close to R290 near room temperature, and the impact of changes in water vapor in the air (the water vapor partial pressure ratio of 100% RH at normal temperature and pressure is about 4%) is usually much higher than the detection accuracy of refrigerant gas leaks (such as the partial pressure ratio is generally 1000ppm-R290), making it difficult for humidity compensation to achieve the desired accuracy.

[0042] Therefore, the gas sensor 100 of the present application has the relationship between the relative thermal conductivity (normalized to air) of air (dry air, no CO2), water vapor, CO2 and refrigerant gas R290 and temperature at a normal pressure of 1 atm, wherein water vapor and air have the same thermal conductivity at about Tc ~ 301C, which is about 0.044W / mK, which means that the change in the humidity of humid air does not change its thermal conductivity, that is, there is no need to do the most complicated humidity compensation. At this temperature, the thermal conductivity of R290 is about 0.058W / mK, which is significantly different, that is, high sensitivity. The gas to be measured works near this temperature, and only relatively simple pressure compensation is required.

[0043] Therefore, the gas sensor 100 according to the embodiment of the present invention is constructed into a dual-temperature-controlled dual-heat plate structure by arranging the first heating plate 20 and the second heating plate 30 on the substrate 10, making full use of the fact that the thermal conductivity of the refrigerant gas in a specific high-temperature range is significantly higher than that of dry air, water vapor, CO2, etc., so as to reduce the interference caused by these environmental change factors, thereby achieving the purpose of improving the device sensitivity, signal-to-noise ratio, etc. At the same time, by utilizing the fact that the thermal conductivity of water vapor in the same high-temperature range is very close to that of dry air, humidity compensation is simplified or even omitted.

[0044] According to an embodiment of the present invention, in the thickness direction of the substrate 10 , the spacing distance between the first heating plate 20 and the second heating plate 30 is 1-5 μm, and the distance between the second heating plate 30 and the substrate 10 is 1-5 μm.

[0045] That is to say, Figure 2 and Figure 3 As shown, in the thickness direction of the substrate 10, the spacing distance between the first heating plate 20 and the second heating plate 30 is Gap2, wherein Gap2 can be 1-5μm, and the distance between the second heating plate 30 and the substrate 10 is Gap1, wherein Gap1 can be 1-5μm. When Gap1 and Gap2 are of appropriate size, it can be ensured that the heat dissipation of the first heating plate 20 and the second heating plate 30 mainly depends on the heat conduction Rth_V1 and Rth_V2 in the vertical direction of the gas, while the thermal radiation and thermal convection can be ignored. Therefore, when the gap of the gas sensor 100 is filled with air, Rth_Vi is only about 7.6E3 (K / W) at normal temperature and pressure, and the influence of other heat dissipation pathways can be ignored. When the first heating plate 20 and the second heating plate 30 work at high temperature, the thermal conductivity of the gas to be measured will generally increase, the thermal resistance between the hot plates will decrease, and the influence of other heat dissipation pathways can be ignored. Since the MEMS volume is extremely small and the heat capacity is extremely low, the response speed is extremely fast, and the thermal time constant of each hot plate is about 0.1ms. At the same time, the gas to be measured works at a high thermal conductivity temperature with high sensitivity, which simplifies the most troublesome humidity compensation and only requires pressure compensation.

[0046] According to an embodiment of the present invention, the number of the first sensing resistors 21 in the first heating plate 20 is one or more, and the number of the second sensing resistors 31 in the second heating plate 30 is one or more.

[0047] In other words, Figure 2 As shown, there can be one first induction resistor 21 in the first heating plate 20, and one second induction resistor 31 in the second heating plate 30, and each induction resistor can be used for heating and temperature measurement. Figure 3 , the first sensing resistor 21 in the first heating plate 20 can be multiple (for example, two), and the second sensing resistor 31 in the second heating plate 30 can be multiple (for example, two), and each sensing resistor can be heated and temperature measured. By arranging the first heating plate 20 and the second heating plate 30 on the substrate 10, the gas sensor 100 is constructed into a dual-temperature controlled double-hot plate structure, making full use of the characteristics that the thermal conductivity of the refrigerant gas in a specific high-temperature range is significantly higher than that of dry air, water vapor, CO2, etc., so as to reduce the interference caused by these environmental change factors, so as to achieve the purpose of improving the device sensitivity, signal-to-noise ratio and other performance. At the same time, by utilizing the characteristics that the thermal conductivity of water vapor in the same high-temperature range is very close to that of dry air, humidity compensation is simplified or even omitted.

[0048] According to one embodiment of the present invention, the cross-sectional length of the first heating plate 20 and the second heating plate 30 is 100-200 μm.

[0049] That is to say, the first heating plate 20 and the second heating plate 30 can be set to be square or circular, and the cross-sectional length of the first heating plate 20 and the second heating plate 30 can be 100-200μm. Gap1 and Gap2 can both be 1-5μm, which can ensure that the heat dissipation of the first heating plate 20 and the second heating plate 30 mainly depends on the heat conduction Rth_V1 and Rth_V2 in the vertical direction of the gas, while thermal radiation and thermal convection can be ignored. Therefore, when the gap of the gas sensor 100 is filled with air, Rth_Vi is only about 7.6E3 (K / W) at normal temperature and pressure, and the influence of other heat dissipation pathways can be ignored. When the first heating plate 20 and the second heating plate 30 work at high temperature, the thermal conductivity of the gas to be measured will generally increase, the thermal resistance between the hot plates will decrease, and the influence of other heat dissipation pathways can be ignored. Since the MEMS volume is very small and the heat capacity is extremely low, the response speed is extremely fast, and the thermal time constant of each hot plate is about 0.1ms. At the same time, the gas to be measured works at a high thermal conductivity temperature with high sensitivity, which simplifies the most troublesome humidity compensation and only requires pressure compensation.

[0050] According to one embodiment of the present invention, the first heating plate 20 includes a first insulating layer 22 which covers the outer periphery of the first sensing resistor 21 , and the second heating plate 30 includes a second insulating layer 32 which covers the outer periphery of the second sensing resistor 31 .

[0051] That is to say, Figure 2 and Figure 3 As shown, the first heating plate 20 includes a first insulating layer 22, which can be coated on the periphery of the first sensing resistor 21, and the second heating plate 30 includes a second insulating layer 32, which can be coated on the periphery of the second sensing resistor 31 to ensure the reliability and life of high temperature operation.

[0052] According to an embodiment of the present invention, the materials of the first sensing resistor 21 and the second sensing resistor 31 are both selected from the group consisting of polysilicon, non-polysilicon, metal, and alloy.

[0053] In other words, the materials of the first sensing resistor 21 and the second sensing resistor 31 are both polysilicon, non-polysilicon, metal or alloy. The metal may be Pt, Pd, W, TaN, Au, Cu, Al, TiN, etc., and the alloy may be NiCr, TiW, etc. The above-mentioned resistor materials have high thermal conductivity, which can ensure the temperature uniformity in the hot plate and improve the measurement accuracy.

[0054] According to an embodiment of the present invention, the thickness of the first sensing resistor 21 and the second sensing resistor 31 are both 0.1-1 μm, and the thickness size is appropriate to improve the measurement accuracy.

[0055] According to an embodiment of the present invention, the materials of the first insulating layer 22 and the second insulating layer 32 are both composite layers of silicon dioxide and silicon-rich silicon nitride, and the thickness is 0.1-1 μm.

[0056] That is to say, the materials of the first insulating layer 22 and the second insulating layer 32 are both a composite layer of silicon dioxide and silicon-rich silicon nitride, and the silicon-rich silicon nitride can be silicon-rich silicon nitride with low tensile stress (250±50MPa), and the silicon-nitrogen atomic ratio is 1:0.9-1.1. In addition, the thickness of the first insulating layer 22 and the second insulating layer 32 are both 0.1-1μm, which can ensure that the structure is flat after release and is not affected by packaging stress.

[0057] In some specific embodiments of the present invention, the gas sensor 100 further includes: a plurality of first beam arms 40 and a plurality of second beam arms 50, wherein the plurality of first beam arms 40 are spaced apart and distributed along the periphery of the first heating plate 20, and are respectively connected to the first heating plate 20 and the substrate 10, and the plurality of second beam arms 50 are spaced apart and distributed along the periphery of the second heating plate 30, and are respectively connected to the second heating plate 30 and the substrate 10. A third sensing resistor 41 is disposed in the first beam arm 40, and a fourth sensing resistor 51 is disposed in the second beam arm 50.

[0058] In other words, Figures 1 to 3 As shown, the gas sensor 100 also includes: a plurality of first beam arms 40 and a plurality of second beam arms 50, the plurality of first beam arms 40 can be spaced apart and distributed along the periphery of the first heating plate 20, and each first beam arm 40 is respectively connected to the first heating plate 20 and the substrate 10. A plurality of second beam arms 50 can be spaced apart and distributed along the periphery of the second heating plate 30, and each second beam arm 50 is respectively connected to the second heating plate 30 and the substrate 10. By designing a lateral heat dissipation path from the hot plate to the substrate 10 (such as the first beam and the second beam arm 50), it can also be ensured that the lateral thermal resistance Rth_L1 / L2 is much higher than Rth_V1 / 2, and can also be ignored. A third induction resistor 41 is provided in the first beam arm 40, and a fourth induction resistor 51 is provided in the second beam arm 50. Each layer of the hot plate is composed of a layer of conductive resistor material (first sensing resistor 21 and second sensing resistor 31), and its corresponding long arm beams (first beam arm 40 and second beam arm 50) contribute the main resistance (third sensing resistor 41 and fourth sensing resistor 51). The four-wire resistance connection can also be used for both heating (such as constant current or constant power mode) and measuring resistance (i.e., temperature).

[0059] The gas sensor 100 of the present invention optimizes the upper and lower heating plates (the first heating plate 20 and the second heating plate 30) to have temperatures of Tc+ΔT and Tc-ΔT, respectively, where Tc is the temperature at which water vapor and air have the same thermal conductivity, such as Tc~301C at normal pressure. Here, the thermal conductivity of air and water vapor is consistent (no need to compensate for humidity), both of which are 0.044W / mK, while R290 is 0.058W / mK, which is significantly higher. As a result, the gas to be measured works at a high thermal conductivity temperature, has high sensitivity, and simplifies the most troublesome humidity compensation, only requiring pressure compensation. The preferred range of ΔT is 10-100K, or 20-50K.

[0060] In the actual calculation process, the area of ​​the first heating plate 20 is S1, the area of ​​the second heating plate 30 is S2, S1 = S2 = (100um) 2, Gap1=Gap2=2um, each long arm beam (first beam arm 40 and second beam arm 50) is 150um long, the cross-sectional area of ​​single-layer polysilicon (third sensing resistor 41 and fourth sensing resistor 51) is 2um wide and 0.5um thick, and wrapped with 10um wide and 0.2+0.2um silicon nitride (the insulating material layer around the third sensing resistor 41 and the fourth sensing resistor 51, which can be understood as the third insulating layer 42 and the fourth insulating layer 52), then Rth_Li~4E5(K / W), Rconvection~2E7(K / W). If the gap is filled with air, Rth_Vi is only about 7.6E3(K / W) at normal temperature and pressure, and the influence of other heat dissipation pathways can be ignored. When the hot plate works at high temperature, the thermal conductivity of the gas to be measured will generally increase, the thermal resistance between the hot plates will decrease, and the influence of other heat dissipation pathways can be ignored. Since the MEMS volume is extremely small and the heat capacity is extremely low, the response speed is extremely fast, and the thermal time constant of each hot plate is about 0.1ms.

[0061] In summary, the gas sensor 100 according to the embodiment of the present invention is constructed into a dual-temperature-controlled dual-heat plate structure by arranging the first heating plate 20 and the second heating plate 30 on the substrate 10, making full use of the fact that the thermal conductivity of the refrigerant gas in a specific high-temperature range is significantly higher than that of dry air, water vapor, CO2, etc., so as to reduce the interference caused by these environmental change factors, thereby achieving the purpose of improving the device sensitivity, signal-to-noise ratio, and other performances. At the same time, by utilizing the fact that the thermal conductivity of water vapor in the same high-temperature range is very close to that of dry air, humidity compensation is simplified or even omitted.

[0062] Although some specific embodiments of the present invention have been described in detail by way of example, it will be appreciated by those skilled in the art that the above examples are for illustration only and are not intended to limit the scope of the present invention. It will be appreciated by those skilled in the art that the above embodiments may be modified without departing from the scope and spirit of the present invention. The scope of the present invention is defined by the appended claims.

Claims

1. A gas sensor (100), characterized in that: include: A substrate (10), wherein a mounting cavity (11) is provided on the substrate (10); A first heating plate (20), wherein a first induction resistor (21) is provided in the first heating plate (20); A second heating plate (30), wherein the first heating plate (20) and the second heating plate (30) are arranged in the mounting cavity (11) of the substrate (10) at a distance from each other, and a second induction resistor (31) is arranged in the second heating plate (30).

2. The gas sensor (100) according to claim 1, characterized in that In the thickness direction of the substrate (10), the spacing distance between the first heating plate (20) and the second heating plate (30) is 1-5 μm, and the distance between the second heating plate (30) and the substrate (10) is 1-5 μm.

3. The gas sensor (100) according to claim 1, characterized in that The number of the first sensing resistors (21) in the first heating plate (20) is one or more, and the number of the second sensing resistors (31) in the second heating plate (30) is one or more.

4. The gas sensor (100) according to claim 1, characterized in that The cross-sectional length of the first heating plate (20) and the second heating plate (30) is 100-200 μm.

5. The gas sensor (100) according to claim 1, characterized in that The first heating plate (20) comprises a first insulating layer (22), the first insulating layer (22) being coated on the periphery of the first sensing resistor (21), and the second heating plate (30) comprises a second insulating layer (32), the second insulating layer (32) being coated on the periphery of the second sensing resistor (31).

6. The gas sensor (100) according to claim 1, characterized in that The material of the first sensing resistor (21) and the second sensing resistor (31) are both one of polysilicon, non-polysilicon, metal or alloy.

7. The gas sensor (100) according to claim 1, characterized in that The thickness of the first sensing resistor (21) and the second sensing resistor (31) are both 0.1-1 μm.

8. The gas sensor (100) according to claim 5, characterized in that The materials of the first insulating layer (22) and the second insulating layer (32) are both composite layers of silicon dioxide and silicon-rich silicon nitride, and have a thickness of 0.1-1 μm.

9. The gas sensor (100) according to claim 1, characterized in that Also includes: A plurality of first beam arms (40) and a plurality of second beam arms (50), wherein the plurality of first beam arms (40) are distributed at intervals along the periphery of the first heating plate (20) and respectively connect the first heating plate (20) and the substrate (10), and the plurality of second beam arms (50) are distributed at intervals along the periphery of the second heating plate (30) and respectively connect the second heating plate (30) and the substrate (10).

10. The gas sensor (100) according to claim 9, characterized in that A third inductive resistor (41) is arranged in the first beam arm (40), and a fourth inductive resistor (51) is arranged in the second beam arm (50).

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