A thermal conductivity type gas sensor and a preparation method and a test method thereof

Abstract

The application provides a thermal conductivity type gas sensor and a preparation method and a test method thereof, and belongs to the technical field of silicon micro-electro-mechanical systems. The thermal conductivity type gas sensor comprises a substrate, a support layer, a detection assembly, a cover plate and an air inlet. One side of the substrate is provided with an air groove. The support layer is located on the side of the substrate with the air groove and comprises a support overhang layer suspended above the air groove. The detection assembly is located on the support overhang layer and comprises, from bottom to top, a heating coil, a protective layer and a columnar fin. The cover plate is located above the support layer, and one side of the cover plate facing the support layer is provided with a containing groove. The detection assembly is located in the opening area of the containing groove. The bottom of the containing groove is provided with an air guide opening. The air inlets are located on both sides of the heating coil and penetrate through the protective layer and the support overhang layer. The thermal conductivity type gas sensor can shield air flow interference, improve response speed and meet the needs of miniaturization and integration.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of silicon micro-electro-mechanical systems (MEMS), and relates to a thermal conductivity type gas sensor and a preparation method and a testing method thereof. BACKGROUND

[0002] With the continuous development of MEMS technology, thermal conductivity type gas sensors based on MEMS technology have been widely used in many fields. Thermal conductivity type gas sensors achieve accurate measurement of gas types or concentrations by detecting the difference in gas thermal conductivity. Due to the high precision and high integration of MEMS technology, sensors manufactured using MEMS technology further realize the advantages of miniaturization, low power consumption, high sensitivity and large-scale batch production on the basis of traditional technology. Thermal conductivity type gas sensors can provide higher performance at a lower cost, and are particularly suitable for gas monitoring applications in the fields of intelligent terminals, portable instruments and Internet of Things.

[0003] Common MEMS thermal conductivity type gas sensors use a suspended membrane formed by a release process. The suspended membrane is formed by stacking a support layer, a metal coil and a protective layer, forming a typical "sandwich" structure. The suspended membrane exchanges heat with the measurement environment, thereby achieving high sensitivity detection of the difference in gas thermal conductivity. However, changes in gas flow will affect the heat transfer process around the heating element of the sensor, thereby disturbing the thermal equilibrium state and temperature distribution of the sensor, causing fluctuations in the measurement signal and affecting the accuracy and stability of the sensor. Some studies use external packaging to shield the gas flow interference, but this method is difficult to meet the needs of mass production and limits the miniaturization of the device. Based on MEMS technology, researchers shield the gas flow interference by packaging gas flow channels on the front and back surfaces of the gas sensor. However, this method usually relies on backside release and double-sided bonding processes, which not only have a complex process flow, but also have high production costs, making it difficult to promote in large-scale applications. Moreover, this packaging method is difficult to achieve a fast response of hundreds of milliseconds. The response time of existing thermal conductivity type hydrogen sensors is usually between 1 second and 20 seconds, which may not be sufficient to provide timely warnings in high-risk scenarios, making it difficult to effectively respond to potential dangers. At the same time, thermal conductivity type gas sensors also have the limitation of lacking gas selectivity, which makes it difficult to accurately distinguish between different gases. For the response time of thermal conductivity type gas sensors, people mostly adopt the method of optimizing the device to improve the response speed. For the selectivity of thermal conductivity type gas sensors, the common method is to combine thermal conductivity type gas sensors with other types of sensors or to use algorithms to compensate for gas flow interference to make up for the shortcomings of thermal conductivity type gas sensors. However, the method of combining other types of sensors limits the miniaturization and integration of the device to some extent, and also significantly increases the cost of use. The algorithm in the method of using algorithms to compensate for gas flow interference is relatively complex, which also further increases the design and production costs of the system.

[0004] Therefore, how to provide a thermal conductivity type gas sensor and a preparation method and a test method thereof to shield air flow interference, meet the needs of miniaturization and integration, and solve the problems of slow response speed and inability to distinguish different gases of the thermal conductivity type gas sensor become an important problem to be solved by the person skilled in the art.

[0005] It should be noted that the above introduction to the technical background is only for the convenience of clearly and completely describing the technical scheme of the present application and facilitating the understanding of the person skilled in the art. The above technical scheme cannot be considered as known to the person skilled in the art only because it is described in the background section of the present application. SUMMARY

[0006] In view of the above-mentioned shortcomings of the prior art, the purpose of the present application is to provide a thermal conductivity type gas sensor and a preparation method and a test method thereof, which are used to solve the problems that the thermal conductivity type gas sensor in the prior art is difficult to meet the needs of miniaturization and integration, and has slow response speed and cannot distinguish different gases.

[0007] To achieve the above-mentioned purpose and other related purposes, the present application provides a thermal conductivity type gas sensor, comprising:

[0008] a substrate, one side of the substrate being provided with an air groove;

[0009] a support layer located on the side of the substrate with the air groove, the support layer comprising a support overhang layer suspended above the air groove;

[0010] a detection assembly located on the support overhang layer, the detection assembly comprising a heating coil, a protective layer and a columnar fin, the heating coil being located on the surface of the support overhang layer, the protective layer being located on the surface of the support overhang layer and covering the heating coil, and the columnar fin being located on the protective layer;

[0011] a cover plate located above the support layer, one side of the cover plate facing the support layer being provided with a containing groove, the detection assembly being located in the opening area of the containing groove, and the groove bottom of the containing groove being provided with a gas guide port to make the containing groove communicate with the outside;

[0012] an air vent located on both sides of the heating coil and penetrating through the protective layer and the support overhang layer, for communicating the containing groove with the air groove.

[0013] Optionally, the support layer is a composite layer, and the composite layer comprises a silicon oxide layer and a silicon nitride layer.

[0014] Optionally, an environmental resistor is arranged on the support layer, and the environmental resistor is located around the support suspended layer, and an opening is formed in the cover plate to expose the environmental resistor.

[0015] Optionally, the metal coil extends zigzag on the support suspended layer.

[0016] Optionally, the cross section of the columnar fin includes any one of a circle, a rectangle and an ellipse.

[0017] Optionally, a heat sink is connected around the top surface of the columnar fin, and a groove is formed in the top surface of the columnar fin.

[0018] Optionally, a heat-conducting layer is arranged on the protection layer and the columnar fin, and the heat-conducting layer includes a nano material with a high thermal conductivity coefficient.

[0019] The application further provides a preparation method of the thermal-conducting gas sensor.

[0020] A substrate is provided, and a support layer is formed on one side of the substrate;

[0021] A metal layer is formed on the support layer, and the metal layer is patterned to form a heating coil;

[0022] A protection layer covering the heating coil is formed on the support layer, and a columnar fin is formed on the protection layer;

[0023] Air vents located on both sides of the heating coil are formed in the protection layer and the support layer, and the substrate is selectively etched based on the air vents to obtain an air groove;

[0024] A cover plate is provided, and a containing groove and an air guide are formed in the cover plate, the containing groove is formed on one side of the cover plate, and the air guide penetrates the bottom of the containing groove;

[0025] One side of the cover plate provided with the containing groove is aligned with and connected to one side of the substrate provided with the columnar fin, wherein the columnar fin is located in the containing groove, and the containing groove is connected to the air groove through the air vents.

[0026] The application further provides a testing method of the thermal-conducting gas sensor.

[0027] The thermal-conducting gas sensor is provided, and the thermal-conducting gas sensor is placed in a background gas sealed space;

[0028] Sample gas is injected into the sealed space at different preset temperatures, the thermal-conducting gas sensor is calibrated, and a required calibration relationship is obtained.

[0029] Injecting a to-be-tested gas into the sealed space, and measuring a voltage value of the thermal conductivity gas sensor at the preset temperature;

[0030] According to the voltage value and the calibration formula, the type and concentration of the to-be-tested gas are obtained, wherein the type of the to-be-tested gas includes one or more.

[0031] As described above, the present application provides a thermal conductivity gas sensor, a preparation method and a testing method. The thermal conductivity gas sensor comprises a substrate, a support layer, a detection assembly, a cover plate and a gas passage. One side of the substrate is provided with an air groove. The support layer is located on the side of the substrate with the air groove and comprises a support overhang layer suspended above the air groove. The detection assembly is located on the support overhang layer and comprises a heating coil, a protective layer and a columnar fin arranged in sequence from bottom to top. The cover plate is located above the support layer, and one side of the cover plate facing the support layer is provided with a containing groove. The detection assembly is located in the opening area of the containing groove. The groove bottom of the containing groove is provided with a gas guide port. The gas passage is located on both sides of the heating coil and penetrates through the protective layer and the support overhang layer. The thermal conductivity gas sensor of the present application can shield airflow interference, improve response speed, and meet the needs of miniaturization and integration. The testing method of the thermal conductivity gas sensor of the present application uses the thermal conductivity gas sensor, and through a preset formula, different to-be-tested gases can be accurately distinguished. BRIEF DESCRIPTION OF DRAWINGS

[0032] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed in the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0033] Figure 1 A structural schematic diagram of the thermal conductivity gas sensor of the present application is shown.

[0034] Figure 2 A top view of another structure of the thermal conductivity gas sensor of the present application is shown.

[0035] Figure 3 A process flow diagram of the preparation method of the thermal conductivity gas sensor of the present application is shown.

[0036] Figure 4 A schematic diagram of the structure obtained after providing a substrate and forming a support layer in the preparation method of the thermal conductivity gas sensor of the present application is shown.

[0037] Figure 5A schematic diagram showing the structure obtained after forming a metal coil and an ambient resistance in the method of fabricating a thermal conductivity type gas sensor of the present application.

[0038] Figure 6 A schematic diagram showing the structure obtained after forming a protective layer and a columnar fin in the method of fabricating a thermal conductivity type gas sensor of the present application.

[0039] Figure 7 A schematic diagram showing the structure obtained after forming a sacrificial layer in the method of fabricating a thermal conductivity type gas sensor of the present application.

[0040] Figure 8 A schematic diagram showing the structure obtained after forming a filling layer in the method of fabricating a thermal conductivity type gas sensor of the present application.

[0041] Figure 9 A schematic diagram showing the structure obtained after forming a vent in the method of fabricating a thermal conductivity type gas sensor of the present application.

[0042] Figure 10 A schematic diagram showing the structure obtained after removing a sacrificial layer in the method of fabricating a thermal conductivity type gas sensor of the present application.

[0043] Figure 11 A schematic diagram showing the structure obtained after providing a cover plate in the method of fabricating a thermal conductivity type gas sensor of the present application.

[0044] Figure 12 A schematic diagram showing the workflow of calibrating in the method of testing a thermal conductivity type gas sensor of the present application.

[0045] Figure 13 A schematic diagram showing the workflow of testing a gas concentration to be tested in the method of testing a thermal conductivity type gas sensor of the present application.

[0046] BRIEF DESCRIPTION OF DRAWINGS

[0047] 1 substrate

[0048] 2 detection assembly

[0049] 201 heating coil

[0050] 202 protective layer

[0051] 203 columnar fin

[0052] 3 cover plate

[0053] 4 vent

[0054] 5 air groove

[0055] 6 support layer

[0056] 7 support overhang layer

[0057] 8 housing groove

[0058] 9 gas inlet

[0059] 10 ambient resistance

[0060] 11 opening

[0061] 12 lead-out pad

[0062] 13 second opening

[0063] 14 heat dissipation fin

[0064] 15 recess

[0065] 16 sacrificial layer

[0066] 17 filling layer

[0067] 18 heat conduction layer

[0068] S1-S6 steps DETAILED DESCRIPTION

[0069] The present application is herein described, by way of example only, with the assistance of specific details to facilitate appreciation of the inventive concepts more fully. The application, however, is not limited to these specific details, which are intended to be illustrative only. Various modifications can be made by those skilled in the art, now or in the future, without departing from the spirit of the present application.

[0070] It is emphasized that the term "comprises / comprising" when used in this specification is taken to specify the presence of stated features, integers, steps or components but does not preclude the presence or addition of one or more other features, integers, steps, components or groups thereof.

[0071] Features described and / or illustrated with respect to one implementation can be used in the same or similar manner in one or more other implementations, in combination with or in place of features in other implementations.

[0072] In the detailed description of embodiments of the application, reference is made to the accompanying drawings, which form a part hereof, and in which are shown by way of illustration various embodiments by which the application can be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the application, and it is to be understood that other embodiments can be utilized and that logical, mechanical and electrical changes can be made without departing from the spirit of the present application. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present application is defined only by the appended claims.

[0073] For convenience, spatially relative terms such as "under," "below," "below," "below," "above," and "on" may be used herein to describe the relationship of one element or feature to other elements or features shown in the drawings. It will be understood that these spatially relative terms are intended to encompass orientations of the device in use or operation in addition to the orientation depicted in the drawings. Additionally, when a layer is referred to as being "between" two layers, it can be the only layer between the two layers, or one or more intervening layers may also be present.

[0074] In the context of the present application, a first feature described as being "above" a second feature may include embodiments where the first and second features are in direct contact, and may also include embodiments where an additional feature is formed between the first and second features, such that the first and second features may not be in direct contact.

[0075] It should be noted that the illustrations provided in this embodiment are only used to schematically illustrate the basic concept of the present invention. Therefore, the illustrations only show components related to the present invention and are not drawn according to the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component can be changed at will, and the component layout type may also be more complicated.

[0076] Example 1

[0077] This embodiment provides a thermal conductivity gas sensor. Figure 1 , which is a schematic structural diagram of the thermal conductivity gas sensor of the present invention, includes a substrate 1, a support layer 6, a detection component 2, a cover plate 3 and a vent 4, wherein an air groove 5 is opened on one side of the substrate 1, the support layer 6 is located on the side of the substrate 1 having the air groove 5, the support layer 6 includes a support suspended layer 7 suspended above the air groove 5, the detection component 2 is located on the support suspended layer 7 and includes a heating coil 201, a protective layer 202 and a columnar fin 203, the heating coil 201 is located on the surface of the support suspended layer 7, the protective layer 20 2 is located on the surface of the supporting suspended layer 7 and covers the heating coil 201, the columnar fins 203 are located on the protective layer 202, the cover plate 3 is located above the supporting layer 6, and the cover plate 3 is provided with a receiving groove 8 on the side facing the supporting layer 6, the detection component 2 is located in the opening area of ​​the receiving groove 8, and the bottom of the receiving groove 8 is provided with an air guide port 9 to connect the receiving groove 8 with the outside world, and the vent 4 is located on both sides of the heating coil 201 and passes through the protective layer 202 and the supporting suspended layer 7, for connecting the receiving groove 8 with the air groove 5.

[0078] Specifically, in the working process of the thermal conductivity gas sensor, the to-be-measured gas enters the accommodating groove 8 through the gas guide port 9, and the resistance of the heating coil 201 changes, and the thermal conductivity gas sensor can realize quantitative measurement of the gas concentration by converting the resistance change into an electric signal. The air groove 5 is located below the support overhanging layer 7, which can effectively utilize the low thermal conductivity of air to play a heat insulation role. The columnar fin 203 is located between the protective layer 202 and the cover plate 3, which can effectively increase the heat dissipation area of the heating coil 201, accelerate the heat exchange between the columnar fin 203 and the surrounding gas, and at the same time, can also provide a spoiler effect, reduce the thickness of the surface thermal boundary layer of the heating coil 201, and reduce the heat conduction distance, thereby improving the response speed of the thermal conductivity gas sensor.

[0079] Specifically, the cover plate 3 provided with the gas guide port 9 provides a gas flow channel, which can effectively reduce the gas flow interference, avoid the influence of gas flow change on the measurement signal of the thermal conductivity gas sensor, and further improve the measurement accuracy of the thermal conductivity gas sensor, so that the thermal conductivity gas sensor performs excellently in a dynamic flow environment. It should be pointed out that the shape of the gas guide port 9 is a sandglass type, which is more conducive to the entry of external gas into the thermal conductivity gas sensor, and improves the working efficiency of the thermal conductivity gas sensor. As an example, the support layer 6 is a composite layer, which includes a silicon oxide layer and a silicon nitride layer.

[0080] As an example, please refer to Figure 2 , which shows a top view of another structure of the thermal conductivity gas sensor of the present application, the support layer 6 is further provided with an ambient resistance 10, the ambient resistance 10 is located around the support overhanging layer 7, and the cover plate 3 is provided with an opening 11 for exposing the ambient resistance 10, the ambient resistance 10 is used to detect the temperature of the external environment in real time when the heating coil 201 is working, when the external temperature changes, the resistance of the ambient resistance 10 also changes, through reasonable circuit design, the interference effect caused by the fluctuation of the ambient temperature can be compensated, the measurement result of the heating coil 201 is compensated and calculated, and the measurement result is corrected to ensure that accurate measurement values are obtained, and the heating coil 201 is always in the best working state. As an example, the support layer 6 is further provided with a lead-out pad 12, and the cover plate 3 is provided with a second opening 13 for exposing the lead-out pad 12, wherein the lead-out pad 12 is electrically connected with the ambient resistance 10 and the heating coil 201 respectively, and is used for electrically leading out the thermal conductivity gas sensor.

[0081] As an example, please refer to Figure 2 , a sectional structure along the AA' direction is shown in Figure 1 , Figure 2Region B shown in the figure constitutes the thermal conductivity gas sensor of this embodiment, and region C constitutes a reference sensor. The reference sensor's cover plate lacks a gas inlet. When the thermal conductivity gas sensor of this embodiment performs gas measurements, the reference sensor resides within the same background gas space and is not in contact with the gas being measured. This provides further compensation calculations and improves the accuracy of the measurement structure.

[0082] As an example, the metal coil extends back and forth on the supporting suspended layer 7 in a zigzag manner to reduce the area occupied by the detection component 2, which is conducive to the miniaturization of the device. In other embodiments, the metal coil can also be in a U-shaped shape. The shape of the metal coil can be determined according to specific circumstances and is not limited here.

[0083] As an example, the top surface of the columnar fin 203 is connected to a heat sink 14, and the top surface of the columnar fin 203 is also provided with a groove 15. The presence of the heat sink 14 and the groove 15 can further enhance the turbulence effect of the columnar fin 203, thereby effectively improving the response speed.

[0084] As an example, the cross section of the columnar fin 203 includes any one of a circular, rectangular and elliptical shape.

[0085] As an example, the thickness of the support layer 6 ranges from 100 nm to 500 nm, and the height of the columnar fins 203 ranges from 1000 nm to 3000 nm.

[0086] As an example, a thermal conductive layer 18 is provided on the protective layer 202 and the columnar fins 203. The thermal conductive layer 18 uses high thermal conductivity nanomaterials, such as nanodiamonds, carbon nanotubes, graphene and other nanomaterials. The high thermal conductivity characteristics of high thermal conductivity nanomaterials can effectively improve the heat transfer efficiency of convection conduction and further improve the sensitivity of the thermal conductivity gas sensor response. It should be pointed out that since high thermal conductivity nanomaterials are difficult to prepare, other gas sensors do not use high thermal conductivity nanomaterials.

[0087] This embodiment of the thermal conductivity gas sensor includes a substrate, an air groove, a support layer, a detection assembly, a cover plate, and a vent. The detection assembly includes a heating coil, a protective layer, and columnar fins. The cover plate is provided with a receiving slot and an air vent. The cover plate shields the thermal conductivity gas sensor from airflow interference. The columnar fins and their turbulent flow effectively improve heat dissipation from the heating coil, reducing the thickness of the thermal boundary layer on its surface, thereby increasing the response speed of the thermal conductivity gas sensor.

[0088] Example 2

[0089] The embodiment provides a preparation method of a thermal conductivity type gas sensor. Figure 3 The embodiment provides a preparation method of a thermal conductivity type gas sensor.

[0090] First, refer to Figure 4 Step S1 is performed: a substrate 1 is provided, and a support layer 6 is formed on one side of the substrate 1.

[0091] As an example, the substrate 1 is an N-type single-polished or double-polished single-crystal silicon wafer with a (111) crystal plane, and the resistivity of the substrate 1 is 1 Ω·cm-10 Ω·cm.

[0092] As an example, the support layer 6 is formed by low-pressure chemical vapor deposition (LPCVD), and in the embodiment, the structure of the support layer 6 is tetraethoxysilane (TEOS)-silicon nitride (SiNx)-tetraethoxysilane (TEOS).

[0093] Again refer to Figure 5 Step S2 is performed: a metal layer is formed on the support layer 6, and the metal layer is patterned to form a heating coil 201.

[0094] As an example, the metal layer includes a Ta layer and a Pt layer on the Ta, the thickness of the Ta layer ranges from 20 nm to 40 nm, and the thickness of the Pt layer ranges from 100 nm to 300 nm.

[0095] As an example, the method for patterning the metal layer includes one of an ion beam etching process and an ion beam stripping process.

[0096] As an example, the method further includes a step of etching the metal layer to form an ambient resistance 10, and in the embodiment, the heating coil 201 and the ambient resistance 10 are patterned from the same metal layer.

[0097] Again refer to Figure 6 Step S3 is performed: a protective layer 202 covering the heating coil 201 is formed on the support layer 6, and a columnar fin 203 is formed on the protective layer 202.

[0098] As an example, the protective layer 202 is formed by plasma-enhanced chemical vapor deposition.

[0099] As an example, the thickness of the protective layer 202 ranges from 100 nm to 500 nm, and in the embodiment, the protective layer 202 includes any one or a combination of silicon oxide and silicon nitride.

[0100] As an example, the protective layer 202 is further provided with an opening 11 exposing the ambient resistance 10.

[0101] As an example, forming the columnar fins 203 on the protective layer 202 includes the following steps:

[0102] (1) Please refer to Figure 7 , a sacrificial layer 16 is deposited on the protective support layer 6 using a plasma-enhanced chemical vapor deposition process, the sacrificial layer 16 covers the protective layer 202, and the sacrificial layer 16 is etched using reactive ion etching or wet etching to form growth holes in the sacrificial layer 16.

[0103] (2) Please refer to Figure 8 , a filling layer 17 is deposited on the sacrificial layer 16 using a plasma-enhanced chemical vapor deposition process and fills the growth holes.

[0104] (3) Please refer to Figure 6 , the filling layer 17 is etched using reactive ion etching or wet etching to form the columnar fins 203. As an example, the top surface of the columnar fins 203 is connected with a heat dissipation fin 14 around the top surface, and the top surface of the columnar fins 203 is also provided with a groove 15. The presence of the heat dissipation fin 14 and the groove 15 can further enhance the turbulence effect of the columnar fin 203 of the heat dissipation element, thereby effectively improving the response speed.

[0105] As an example, the sacrificial layer 16 includes any one or combination of single crystal silicon and polycrystalline silicon, and the thickness of the sacrificial layer 16 ranges from 1000 nm to 3000 nm.

[0106] As an example, the filling layer 17 includes any one of silicon oxide and silicon nitride.

[0107] As an example, please refer to Figure 1 , further including the step of forming a heat-conducting layer 18 on the protective layer 202 and the columnar fins 203, the heat-conducting layer 18 is formed by using a spotting technique, including the following steps:

[0108] (1) Nanomaterial dispersion liquid preparation: a suitable amount of nanoparticles is dissolved using a dispersant and ultrasonic dispersion is performed to prepare the required nanomaterial dispersion liquid.

[0109] (2) Surface cleaning: the surface of the protective layer 202 and the columnar fins 203 is cleaned using plasma.

[0110] (3) Spotting and particle deposition: uniform spotting is performed on the surface of the protective layer 202 and the columnar fins 203 using appropriate spotting parameters.

[0111] (4) Post-processing: The spotted structure is placed in a clean environment for natural drying or rapid drying in a low-temperature oven to avoid particle movement.

[0112] Specifically, nanomaterials with high thermal conductivity are attached to the surfaces of the protective layer 202 and the columnar fins 203 using a spotting technique. By utilizing the high thermal conductivity of the nanomaterials, the heat transfer efficiency of convection conduction can be greatly improved, thereby enhancing the response sensitivity.

[0113] See also Figures 9 to 10 , executing step S4: forming vents 4 on both sides of the heating coil 201 in the protective layer 202 and the support layer 6, and selectively etching the substrate 1 based on the vents 4 to obtain air grooves 5. Figure 9 It is a schematic diagram showing the structure obtained after forming the vent 4 in the preparation method of the thermal conductivity gas sensor of the present invention, Figure 10 Schematic diagram showing the structure obtained after removing the sacrificial layer 16 in the method for preparing the thermal conductivity gas sensor of the present invention.

[0114] As an example, the vent 4 is formed by a silicon deep reactive ion etching process. The depth of the vent 4 is determined according to the structural requirements and is not limited here.

[0115] As an example, the etching solution used in the selective etching includes any one of KOH and TMAH (tetramethylammonium hydroxide, 25%).

[0116] As an example, after the air groove 5 is formed, the method further includes removing the sacrificial layer 16 and cleaning and drying the air groove 5 .

[0117] See also Figure 11 , perform step S5: provide a cover plate 3, form a receiving groove 8 and an air guide port 9 in the cover plate 3, the receiving groove 8 is opened on one side of the cover plate 3, and the air guide port 9 passes through the bottom of the receiving groove 8.

[0118] As an example, the cover plate 3 is an N-type double-polished single-crystal silicon substrate, and the resistivity of the cover plate 3 is 1Ω·cm to 10Ω·cm.

[0119] As an example, the method of forming the receiving groove 8 and the gas guide port 9 includes wet etching, and the etching solution includes KOH.

[0120] See also Figure 1S6: aligning the side of the cover plate 3 provided with the accommodating groove 8 with the side of the substrate 1 provided with the columnar fin 203, and connecting the columnar fin 203 with the accommodating groove 8, wherein the accommodating groove 8 is connected with the air groove 5 through the air vent 4.

[0121] For example, the cover plate is connected with the substrate by a bonding technique, and in this embodiment, a single-side bonding technique is preferably adopted, which can simplify the manufacturing process and reduce the manufacturing cost.

[0122] For example, the depth of the accommodating groove 8 is greater than the height of the columnar fin 203, so as to ensure a certain spacing between the accommodating groove 8 and the columnar fin 203, and the depth of the accommodating groove 8 can be determined according to the structure requirement and is not limited here. The manufacturing method of the thermal conductivity gas sensor in this embodiment adopts a (111) crystal direction silicon wafer as the substrate, and the thermal conductivity gas sensor is manufactured by a single-side manufacturing and single-side bonding process, which has the advantages of low manufacturing cost, good consistency, simple process, and meeting the needs of miniaturization and integration.

[0123] Embodiment Three

[0124] The embodiment provides a testing method of the thermal conductivity gas sensor, which comprises the following steps:

[0125] Step one: providing any one of the thermal conductivity gas sensors in the embodiment one, and placing the thermal conductivity gas sensor in a background gas sealed space.

[0126] Step two: injecting sample gas into the sealed space at different preset temperatures, calibrating the thermal conductivity gas sensor, and obtaining a required calibration relationship.

[0127] Step three: injecting a to-be-tested gas into the sealed space, and measuring the voltage value of the thermal conductivity gas sensor at the preset temperature.

[0128] Step four: obtaining the type and concentration of the to-be-tested gas according to the voltage value and the calibration relationship, wherein the type of the to-be-tested gas comprises one or more.

[0129] For details, please refer to Figure 12 which shows a working flow chart of the calibration in the testing method of the thermal conductivity gas sensor, and comprises the following steps:

[0130] S1.1. calibrating with nitrogen as the background gas.

[0131] S1.2. At temperatures T1 and T2, perform response curve calibration on sample gas Q1 and sample gas Q2, respectively, and calculate the response ratios at the two temperatures, which are recorded as K1 and K2. The specific operations are as follows:

[0132] (1) At temperature T1, inject sample gas Q1 and sample gas Q2 into the enclosed space respectively, and measure the voltage value B corresponding to the sample gas Q1 T1 , and the voltage value D corresponding to the sample gas Q2 T1 .

[0133] (2) At temperature T2, inject sample gas Q1 and sample gas Q2 into the enclosed space respectively, and measure the voltage value B corresponding to the sample gas Q1 T2 , and the voltage value D corresponding to the sample gas Q2 T2 .

[0134] (3) According to the voltage value B T1 And the voltage value B T2 , the ratio factor K1=B of the sample gas Q2 is obtained T1 / B T2 And the ratio factor K2=D of the sample gas Q2 T1 / D T2 .

[0135] S1.3. Perform fitting to obtain the calibration relationship between the background gas and sample gas concentrations and the voltage value. The specific operation is:

[0136] (1) According to the voltage value B T1 And the voltage value D T1 , respectively fitting the concentration Z of the nitrogen (ie background gas) and the concentration A of the sample gas Q1 and the voltage value B of the thermal conductivity gas sensor T1 Relationship B T1 =F(Z, A); the concentration Z of the nitrogen gas and the concentration C of the sample gas Q2 and the voltage value D of the thermal conductivity gas sensor T1 The relationship D T1 =F(Z,C).

[0137] (2) According to the voltage value B T2 And the voltage value D T2 , respectively fitting the concentration Z of the nitrogen gas and the concentration A of the sample gas Q1 and the voltage value B of the thermal conductivity gas sensor T2 Relationship B T2 =F(Z, A); the concentration Z of the nitrogen gas and the concentration C of the sample gas Q2 and the voltage value D of the thermal conductivity gas sensor T2The relationship DT2=F(Z,C).

[0138] As an example, the background gas and the sample gas are of different types and will not chemically react. In other embodiments, the background gas may also be other suitable gases, preferably inert gases such as argon.

[0139] S1.4. Determine the weighting factors corresponding to nitrogen and sample gas, ignore the effect of mixing on thermal conductivity, and fit the calibration relationship between voltage value and nitrogen and sample gas concentration. The specific operation is:

[0140] According to the relationship B T1 =F(Z, A) and D T1 =F(Z, C) or relation B T2 =F(Z, A) and D T2 =F(Z, C), calculate the weight factors corresponding to the nitrogen concentration Z, the concentration A of the sample gas Q1, and the concentration C of the sample gas Q2, and fit the relationship between the voltage value V of the thermal conductivity gas sensor and the nitrogen concentration Z, the concentration A of the sample gas Q1, and the concentration C of the sample gas Q2: V=F(Z, A, C).

[0141] For details, please refer to Figure 13 , which shows a workflow diagram for testing the concentration of a gas to be tested in the thermal conductivity gas sensor testing method of the present invention, including the following steps:

[0142] S1.1. Introduce the gas to be tested, that is, inject the gas to be tested into the enclosed space.

[0143] S1.2. Measure the gas to be tested at temperatures T1 and T2 respectively, and calculate the K value at that temperature. The specific operation is:

[0144] (1) The voltage value V of the thermal conductivity gas sensor is measured at temperatures T1 and T2 respectively. T1 and V T2 .

[0145] (2) According to the voltage value V T1 And the voltage value V T2 , we get the ratio factor K=V T1 / V T2 .

[0146] S1.3. Determine the K value and use different calibration equations to determine the type and concentration of the gas to be measured. The specific operations are:

[0147] (1) When K=K1, it is determined that the gas to be measured is Q1, and according to the relationship B T1 =F(Z, A) or B T2 =F(Z,

[0148] A) Calculate the output binary gas concentration, i.e. the concentration of each of the nitrogen gas (i.e. background gas) and the gas to be measured Q1.

[0149] (2) When K = K2, it is determined that the gas to be measured is Q2, and the concentration of each of the nitrogen gas (i.e. background gas) and the gas to be measured Q2 is obtained according to the relationship D T1 = F(Z, C) or D T2 = F(Z,

[0150] C) Calculate the binary gas concentration, i.e. the concentration of each of the nitrogen gas (i.e. background gas) and the gas to be measured Q2.

[0151] (3) When K≠K1 and K≠K2, it is determined that the gas to be measured is a mixed gas of gas Q1 and gas Q2, and the ternary gas concentration, i.e. the concentration of each of the nitrogen gas (i.e. background gas), the gas Q1 and the gas Q2, is obtained according to the relationship V = F(Z, A, C).

[0152] As an example, the sample gas Q1 is hydrogen and the sample gas Q2 is carbon monoxide, and in other embodiments, the sample gas Q1 and sample gas Q2 can also be other gases, and it should be noted that there is no chemical reaction between the sample gas and the background gas, and there is also no chemical reaction between the sample gas Q1 and sample gas Q2 when they are mixed for testing.

[0153] The test method of the thermal conductivity gas sensor of the present embodiment can identify the type and composition of the gas by testing at multiple temperatures.

[0154] In summary, the present application provides a thermal conductivity gas sensor, a preparation method and a test method. The thermal conductivity gas sensor comprises a substrate, a support layer, a detection assembly, a cover plate and an air inlet. One side of the substrate is provided with an air groove. The support layer is located on the side of the substrate with the air groove and comprises a support overhang layer suspended above the air groove. The detection assembly is located on the support overhang layer and comprises a heating coil, a protective layer and a columnar fin arranged in sequence from bottom to top. The cover plate is located above the support layer, and one side of the cover plate facing the support layer is provided with a receiving groove. The detection assembly is located in the opening area of the receiving groove. The bottom of the receiving groove is provided with a gas guide port. The air inlet is located on both sides of the heating coil and penetrates through the protective layer and the support overhang layer. The thermal conductivity gas sensor of the present application can shield air flow interference, improve response speed, and meet the needs of miniaturization and integration. The test method of the thermal conductivity gas sensor of the present application uses the thermal conductivity gas sensor, and through a pre-set formula, different gases to be measured can be accurately distinguished. Therefore, the present application effectively overcomes the shortcomings of the prior art and has high industrial utilization value.

[0155] The above embodiments are only illustrative of the principles of the present application and its efficacy, and are not intended to limit the present application. Any modification or change made by any person skilled in the art without departing from the spirit and scope of the present application shall be covered by the claims of the present application.

Claims

1. A thermal conductivity type gas sensor characterized by comprising: The application relates to a thermal conductivity type gas sensor. The substrate has an air groove on one side thereof; a support layer is arranged on the side of the substrate with the air groove, and the support layer comprises a support overhang layer suspended above the air groove; a detection assembly is arranged on the support overhang layer, and the detection assembly comprises a heating coil, a protective layer and columnar fins; the heating coil is arranged on the surface of the support overhang layer; the protective layer is arranged on the surface of the support overhang layer and covers the heating coil; the columnar fins are arranged on the protective layer; the top surface of the columnar fins is connected with radiating fins around the top surface; and grooves are formed in the top surface of the columnar fins; a cover plate is arranged above the support layer, and the cover plate is provided with a containing groove on the side facing the support layer; the detection assembly is arranged in the opening area of the containing groove; the bottom of the containing groove is provided with a gas guide opening so that the containing groove is communicated with the outside; and air vents are arranged on both sides of the heating coil and penetrate through the protective layer and the support overhang layer, so as to communicate the containing groove with the air groove. The support layer is a composite layer, and the composite layer comprises a silicon oxide layer and a silicon nitride layer. The support layer is further provided with an ambient resistance, the ambient resistance is arranged around the support overhang layer, and the cover plate is provided with an opening exposing the ambient resistance. The heating coil is in a back-and-forth zigzag extension shape on the support overhang layer. The cross section of the columnar fins comprises any one of a circle, a rectangle and an ellipse.

2. The thermal conductivity gas sensor according to claim 1, characterized by: The protective layer and the columnar fins are both provided with a heat-conducting layer, and the heat-conducting layer comprises a nano material with a high heat conductivity coefficient.

3. The thermal conductivity gas sensor according to claim 1, characterized by: The application further discloses a method for manufacturing the thermal conductivity type gas sensor.

4. The thermal conductivity gas sensor of claim 1, wherein: The application further discloses a method for manufacturing the thermal conductivity type gas sensor.

5. The thermal conductivity gas sensor of claim 1, wherein: The application further discloses a method for manufacturing the thermal conductivity type gas sensor.

6. The thermal conductivity gas sensor of claim 1, wherein: The application further discloses a method for manufacturing the thermal conductivity type gas sensor.

7. A method of manufacturing a thermal conductivity type gas sensor, characterized by The application further discloses a method for manufacturing the thermal conductivity type gas sensor. The application further discloses a method for manufacturing the thermal conductivity type gas sensor. The application further discloses a method for manufacturing the thermal conductivity type gas sensor. The application further discloses a method for manufacturing the thermal conductivity type gas sensor. The application further discloses a method for manufacturing the thermal conductivity type gas sensor. The application further discloses a method for manufacturing the thermal conductivity type gas sensor. The application further discloses a method for manufacturing the thermal conductivity type gas sensor.

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