Heat conduction type gas sensor and preparation method and test method thereof

Abstract

The invention 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 supporting layer, a detection assembly, a cover plate and a ventilation port, the supporting layer is located on the face, provided with the air groove, of the substrate and comprises a supporting suspension layer suspended above the air groove, the detection assembly is located on the supporting suspension layer and comprises a heating coil, a protection layer and columnar fins which are sequentially arranged from bottom to top, the cover plate is located above the supporting layer, and a containing groove is formed in the face, facing the supporting layer, of the cover plate. The detection assembly is located in an opening area of the containing groove, the groove bottom of the containing groove is provided with an air guiding opening, and the air guiding openings are located in the two sides of the heating coil and penetrate through the protection layer and the supporting suspension layer. The heat conduction type gas sensor can shield airflow interference, improve the response speed and meet the requirements for miniaturization and integration.

Description

Technical Field

[0001] The present invention belongs to the field of silicon microelectromechanical technology, and relates to a thermal conductivity type gas sensor, a preparation method thereof and a testing method thereof. Background Art

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

[0003] Common MEMS thermal conductivity type gas sensors adopt a suspended membrane formed by a release process. The suspended membrane is formed by superimposing a support layer, a metal coil and a protective layer, forming a typical "sandwich" type. The suspended membrane exchanges heat with the measurement environment to achieve high-sensitivity detection of the difference in gas thermal conductivity. However, the change in air 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, resulting in fluctuations in the measurement signal and affecting the accuracy and stability of the sensor. Some studies have achieved the function of shielding air flow interference by using external packaging, but such methods are difficult to meet the requirements of mass production and limit the miniaturization development of the device. Based on MEMS technology, researchers have shielded air flow interference by simultaneously packaging gas flow channels on the front and back of the gas sensor. However, this method usually relies on backside release and double-sided bonding processes, which not only have complex process flows, but also have high production costs, making it difficult to be popularized in large-scale applications, and this packaging method is difficult to achieve a rapid response 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 achieve timely warning in high-risk scenarios and is difficult to effectively respond to potential dangers. At the same time, the thermal conductivity type gas sensor also has the limitation of lack of gas selectivity during the detection process and is difficult to accurately distinguish different gases. For the response time of the thermal conductivity type gas sensor, people mostly adopt the method of optimizing the device to improve the response speed. For the selectivity of the thermal conductivity type gas sensor, currently it is common to use the thermal conductivity type gas sensor in combination with other types of sensors or to compensate for air flow interference by using an algorithm to make up for this shortcoming of the thermal conductivity type gas sensor. However, the method of combining other types of sensors limits the miniaturization and integration of the device to a certain extent, and also significantly increases the use cost. The algorithm implementation in the method of compensating for air flow interference by using an algorithm is relatively complex and will also further increase the design and production costs of the system.

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

[0005] It should be noted that the above introduction of the technical background is only for the convenience of clearly and completely explaining the technical solution of the present application and facilitating the understanding of those skilled in the art. It cannot be considered that the above technical solutions are well-known to those skilled in the art just because these solutions are described in the background art part of the present application. Summary of the Invention

[0006] In view of the above-mentioned disadvantages of the prior art, the purpose of the present invention is to provide a thermal conductivity gas sensor, a preparation method thereof, and a testing method thereof, which are used to solve the problems that the thermal conductivity gas sensor in the prior art is difficult to meet the requirements of miniaturization and integration, and has a slow response speed and inability to distinguish different gases.

[0007] To achieve the above object and other related objects, the present invention provides a thermal conductivity gas sensor, including:

[0008] A substrate, on one side of which an air groove is formed;

[0009] A support layer, located on the side of the substrate having the air groove, and the support layer includes a support suspension layer suspended above the air groove;

[0010] A detection component, located on the support suspension layer, and the detection component includes a heating coil, a protective layer, and columnar fins. The heating coil is located on the surface of the support suspension layer, the protective layer is located on the surface of the support suspension layer and covers the heating coil, and the columnar fins are located on the protective layer;

[0011] A cover plate, located above the support layer, and on the side of the cover plate facing the support layer, a receiving groove is provided. The detection component is located in the opening area of the receiving groove, and an air guide port is provided at the bottom of the receiving groove to communicate the receiving groove with the outside;

[0012] Air vents, located on both sides of the heating coil and penetrating through the protective layer and the support suspension layer, are used to communicate the receiving groove with the air groove.

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

[0014] Optionally, an environmental resistor is further provided on the support layer. The environmental resistor is located around the support suspension layer, and an opening exposing the environmental resistor is formed in the cover plate.

[0015] Optionally, the metal coil extends in a back-and-forth zigzag manner on the support suspension layer.

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

[0017] Optionally, heat sinks are connected to the periphery of the top surface of the columnar fin, and a groove is further formed on the top surface of the columnar fin.

[0018] Optionally, heat conduction layers are provided on both the protective layer and the columnar fin. The heat conduction layer includes a nano material with a high thermal conductivity coefficient.

[0019] The present invention also provides a method for manufacturing a thermal conductivity type gas sensor, including the following steps:

[0020] Provide a substrate, and form a support layer on one side of the substrate;

[0021] Form a metal layer on the support layer, and pattern the metal layer to form a heating coil;

[0022] Form a protective layer covering the heating coil on the support layer, and form columnar fins on the protective layer;

[0023] Form air vents on both sides of the heating coil in the protective layer and the support layer, and perform selective etching on the substrate based on the air vents to obtain air grooves;

[0024] Provide a cover plate, and form a receiving groove and a gas guiding port in the cover plate. The receiving groove is formed on one side of the cover plate, and the gas guiding port penetrates through the bottom of the receiving groove;

[0025] Align and join the side of the cover plate with the receiving groove to the side of the substrate with the columnar fins. Among them, the columnar fins are located in the receiving groove, and the receiving groove is communicated with the air grooves through the air vents.

[0026] The present invention also provides a method for testing a thermal conductivity type gas sensor, including the following steps:

[0027] Provide the thermal conductivity type gas sensor as described in any one of the above, and place the thermal conductivity type gas sensor in a closed space of a background gas;

[0028] At different preset temperatures, inject sample gas into the closed space, calibrate the thermal conductivity type gas sensor, and obtain the required calibration relationship;

[0029] Inject the gas to be measured into the closed space, and measure the voltage value of the thermal conductivity gas sensor at the preset temperature;

[0030] Obtain the type and concentration of the gas to be measured according to the voltage value and the calibration relational expression, wherein the type of the gas to be measured includes one or more.

[0031] As described above, the present invention provides a thermal conductivity gas sensor, a preparation method and a testing method. The thermal conductivity gas sensor includes a substrate, a support layer, a detection component, a cover plate and a vent. Wherein, an air groove is formed on one side of the substrate, the support layer is located on the side of the substrate with the air groove and includes a support suspension layer suspended above the air groove, the detection component is located on the support suspension layer and includes a heating coil, a protective layer and columnar fins arranged in sequence from bottom to top, the cover plate is located above the support layer, and a receiving groove is arranged on the side of the cover plate facing the support layer, the detection component is located in the opening area of the receiving groove, a gas guide port is arranged at the bottom of the receiving groove, and the vent is located on both sides of the heating coil and penetrates through the protective layer and the support suspension layer. The thermal conductivity gas sensor of the present invention can shield the interference of air flow, improve the response speed, and meet the requirements of miniaturization and integration. And the testing method of the thermal conductivity gas sensor of the present invention uses the thermal conductivity gas sensor, and through a preset formula, different gases to be measured can be accurately distinguished. Description of the Drawings

[0032] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0033] Figure 1 It shows a schematic structural diagram of a thermal conductivity gas sensor of the present invention.

[0034] Figure 2 It shows a top view of another structure of the thermal conductivity gas sensor of the present invention.

[0035] Figure 3 It shows a process flow chart of the preparation method of the thermal conductivity gas sensor of the present invention.

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

[0037] Figure 5Schematic diagram of the structure obtained after forming the metal coil and the environmental resistor in the preparation method of the thermal conductivity gas sensor of the present invention.

[0038] Figure 6 Schematic diagram of the structure obtained after forming the protective layer and the columnar fins in the preparation method of the thermal conductivity gas sensor of the present invention.

[0039] Figure 7 Schematic diagram of the structure obtained after forming the sacrificial layer in the preparation method of the thermal conductivity gas sensor of the present invention.

[0040] Figure 8 Schematic diagram of the structure obtained after forming the filling layer in the preparation method of the thermal conductivity gas sensor of the present invention.

[0041] Figure 9 Schematic diagram of the structure obtained after forming the ventilation port in the preparation method of the thermal conductivity gas sensor of the present invention.

[0042] Figure 10 Schematic diagram of the structure obtained after removing the sacrificial layer in the preparation method of the thermal conductivity gas sensor of the present invention.

[0043] Figure 11 Schematic diagram of the structure providing the cover plate in the preparation method of the thermal conductivity gas sensor of the present invention.

[0044] Figure 12 Flowchart of the calibration operation in the test method of the thermal conductivity gas sensor of the present invention.

[0045] Figure 13 Flowchart of the operation for testing the concentration of the gas to be measured in the test method of the thermal conductivity gas sensor of the present invention.

[0046] Description of the reference numerals

[0047] 1 Substrate

[0048] 2 Detection assembly

[0049] 201 Heating coil

[0050] 202 Protective layer

[0051] 203 Columnar fins

[0052] 3 Cover plate

[0053] 4 Ventilation port

[0054] 5 Air groove

[0055] 6 Support layer

[0056] 7 Support suspension layer

[0057] 8 Accommodating groove

[0058] 9 Air guide port

[0059] 10 Environmental resistance

[0060] 11 Opening

[0061] 12 Lead-out pad

[0062] 13 Second opening

[0063] 14 Heat sink

[0064] 15 Groove

[0065] 16 Sacrificial layer

[0066] 17 Filling layer

[0067] 18 Heat conduction layer

[0068] Steps S1 to S6 Specific implementation manner

[0069] The following describes the implementation manners of the present invention through specific specific examples. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific implementation manners. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0070] It should be emphasized that the term "including / comprising" when used herein refers to the presence of features, whole, steps or components, but does not exclude the presence or addition of one or more other features, whole, steps or components.

[0071] Features described and / or shown for one implementation manner can be used in the same or similar manner in one or more other implementation manners, combined with features in other implementation manners, or replace features in other implementation manners.

[0072] When detailing the embodiments of the present invention, for the convenience of description, the schematic diagrams showing the device will be enlarged locally not in accordance with the general ratio, and the schematic diagrams are only examples and should not limit the scope of protection of the present invention herein. In addition, in actual production, three-dimensional spatial dimensions including length, width and depth should be included.

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

[0074] In the context of the present application, the described first feature being "above" the second feature may include embodiments where the first and second features are in direct contact, and may also include embodiments where additional features are 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 only schematically illustrate the basic concept of the present invention. Therefore, only the components related to the present invention are shown in the illustrations, rather than being drawn according to the number, shape, and size of the components in actual implementation. The type, quantity, and proportion of each component in actual implementation can be arbitrarily changed, and the component layout type may also be more complex.

[0076] Embodiment 1

[0077] This embodiment provides a thermal conductivity gas sensor. Please refer to Figure 1 , which shows a schematic structural diagram of the thermal conductivity gas sensor of the present invention, including a substrate 1, a support layer 6, a detection component 2, a cover plate 3, and a ventilation port 4. Among them, an air groove 5 is formed on one surface of the substrate 1, the support layer 6 is located on the surface of the substrate 1 having the air groove 5, the support layer 6 includes a support suspension layer 7 suspended above the air groove 5, the detection component 2 is located on the support suspension layer 7 and includes a heating coil 201, a protective layer 202, and columnar fins 203. The heating coil 201 is located on the surface of the support suspension layer 7, the protective layer 202 is located on the surface of the support suspension 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 support layer 6, and a receiving groove 8 is provided on the surface of the cover plate 3 facing the support layer 6. The detection component 2 is located in the opening area of the receiving groove 8. A gas guide port 9 is provided at the bottom of the receiving groove 8 to communicate the receiving groove 8 with the outside. The ventilation port 4 is located on both sides of the heating coil 201 and penetrates through the protective layer 202 and the support suspension layer 7 for communicating the receiving groove 8 with the air groove 5.

[0078] Specifically, when the thermal conductivity gas sensor is working, the gas to be measured enters the accommodation groove 8 through the air guide port 9. The resistance of the heating coil 201 will change. By converting the resistance change into an electrical signal, the thermal conductivity gas sensor can achieve quantitative measurement of the gas concentration. Among them, the air groove 5 is located below the support suspension layer 7, and 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 flow disturbance 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 air guide port 9 provides a gas flow path, which can effectively reduce the gas flow interference, avoid the influence of air flow changes on the measurement signal of the thermal conductivity gas sensor, and can further improve the measurement accuracy of the thermal conductivity gas sensor, making the thermal conductivity gas sensor perform excellently in a dynamic flow environment. It should also be noted that the shape of the air guide port 9 is hourglass-shaped, which is more conducive to the external gas entering the thermal conductivity gas sensor and improving the working efficiency of the thermal conductivity gas sensor. As an example, the support layer 6 is a composite layer, and the composite layer 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 invention. An environmental resistor 10 is further provided on the support layer 6. The environmental resistor 10 is located around the support suspension layer 7, and an opening 11 exposing the environmental resistor 10 is provided in the cover plate 3. The environmental resistor 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 value of the environmental resistor 10 also changes. Through reasonable circuit design, the interference effect caused by environmental temperature fluctuations can be compensated, the compensation calculation of the measurement result of the heating coil 201 can be realized, the measurement result can be corrected to ensure an accurate measurement value, and the heating coil 201 can always be in the best working state. As an example, an extraction pad 12 is further provided on the support layer 6, and a second opening 13 exposing the extraction pad 12 is provided in the cover plate 3. Among them, the extraction pad 12 is electrically connected to the environmental resistor 10 and the heating coil 201 respectively, and is used for electrically extracting the thermal conductivity gas sensor.

[0081] As an example, please refer to Figure 2 , a cross-sectional structure diagram along the AA' direction is as Figure 1 shown, Figure 2The B region shown in the figure constitutes a thermal conductivity gas sensor of this embodiment, and the C region constitutes a reference sensor. There is no air guide port on the cover plate of the reference sensor. When the thermal conductivity gas sensor of this embodiment measures gas, the reference sensor and the thermal conductivity gas sensor of this embodiment are in the same background gas space and do not come into contact with the gas to be measured, which is used to further provide compensation calculation and improve the accuracy of the measurement structure.

[0082] As an example, the metal coil extends back and forth tortuously on the support suspension layer 7 to reduce the area occupied by the detection component 2, which is beneficial to the miniaturization of the device. In other embodiments, the metal coil can also be in a square shape, and the shape of the metal coil can be determined according to specific circumstances, and no excessive restrictions are made here.

[0083] As an example, heat sinks 14 are connected to the periphery of the top surface of the columnar fin 203, and a groove 15 is also provided on the top surface of the columnar fin 203. The presence of the heat sinks 14 and the groove 15 can further enhance the flow disturbance 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 circle, a rectangle, and an ellipse.

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

[0086] As an example, heat conduction layers 18 are provided on both the protective layer 202 and the columnar fin 203. The heat conduction layer 18 uses nano materials with high thermal conductivity coefficients, such as nano diamond, carbon nanotube, graphene and other nano materials. Through the high thermal conductivity characteristics of the nano materials with high thermal conductivity coefficients, the heat transfer efficiency of convective conduction can be effectively improved, and the sensitivity of the response of the thermal conductivity gas sensor can be further enhanced. It should be noted that due to the difficulty in preparing nano materials with high thermal conductivity coefficients, other gas sensors do not use nano materials with high thermal conductivity coefficients.

[0087] The thermal conductivity gas sensor of this embodiment includes a substrate, an air groove, a support layer, a detection component, a cover plate and an air vent. Among them, the detection component includes a heating coil, a protective layer, and columnar fins. The cover plate is provided with a receiving groove and an air guide port. The thermal conductivity gas sensor of this embodiment can shield the airflow interference through the cover plate. By using the columnar fins and their flow disturbance effect, the heat dissipation of the heating coil can be effectively improved, and the thickness of the thermal boundary layer on its surface can be reduced, thereby improving the response speed of the thermal conductivity gas sensor.

[0088] Embodiment 2

[0089] This embodiment provides a method for fabricating a thermal conductivity gas sensor. Please refer to Figure 3 , which shows the process flow chart of the method for fabricating the thermal conductivity gas sensor of the present invention, including the following steps:

[0090] First, please refer to Figure 4 , and perform step S1: Provide a substrate 1, and form a support layer 6 on one side of the substrate 1.

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

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

[0093] Then, please refer to Figure 5 , and perform step S2: Form a metal layer on the support layer 6, and pattern the metal layer 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 range of the Ta layer is 20 nm to 40 nm, and the thickness range of the Pt layer is 100 nm to 300 nm.

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

[0096] As an example, it further includes the step of etching the metal layer to form an ambient resistance 10. In this embodiment, the heating coil 201 and the ambient resistance 10 are formed by patterning the same metal layer.

[0097] Then, please refer to Figure 6 , and perform step S3: Form a protective layer 202 covering the heating coil 201 on the support layer 6, and form columnar fins 203 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 range of the protective layer 202 is 100 nm to 500 nm. In this 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) Refer to Figure 7 , deposit a sacrificial layer 16 on the protective support layer 6 by using a plasma enhanced chemical vapor deposition process. The sacrificial layer 16 covers the protective layer 202, and etch the sacrificial layer 16 by using reactive ion etching or wet etching to form growth holes in the sacrificial layer 16.

[0103] (2) Refer to again Figure 8 , deposit a filling layer 17 on the sacrificial layer 16 by using a plasma enhanced chemical vapor deposition process and fill the growth holes.

[0104] (3) Refer to again Figure 6 , etch the filling layer 17 by using reactive ion etching or wet etching to form the columnar fins 203. As an example, heat dissipation fins 14 are connected around the top surface of the columnar fins 203, and a groove 15 is further formed on the top surface of the columnar fins 203. The presence of the heat dissipation fins 14 and the groove 15 can further enhance the flow disturbance effect of the columnar fins 203 of the heat dissipation element, thereby effectively improving the response speed.

[0105] As an example, the sacrificial layer 16 includes any one or a combination of single crystal silicon and polycrystalline silicon, and the thickness range of the sacrificial layer 16 is 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, refer to again Figure 1 , and further includes 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) Preparation of nano material dispersion liquid: Dissolve an appropriate amount of nano particles by using a dispersant and perform ultrasonic dispersion to prepare the required nano material dispersion liquid.

[0109] (2) Surface cleaning: Clean the surfaces of the protective layer 202 and the columnar fins 203 by using plasma.

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

[0111] (4) Post-treatment: Place the spotted structure in a clean environment and let it dry naturally or use a low-temperature oven for rapid drying to avoid particle movement.

[0112] Specifically, a nanomaterial with high thermal conductivity is attached to the surfaces of the protective layer 202 and the columnar fins 203 by using a spotting technique. By utilizing the high thermal conductivity characteristics of the nanomaterial, the heat transfer efficiency of convective conduction can be greatly improved, and the response sensitivity can be enhanced.

[0113] Please refer to Figures 9 to 10 again, and perform step S4: Form air vents 4 on both sides of the heating coil 201 in the protective layer 202 and the support layer 6, and selectively etch the substrate 1 based on the air vents 4 to obtain air grooves 5. Among them, Figure 9 FIG. shows a schematic diagram of the structure obtained after forming the air vents 4 in the preparation method of the thermal conductivity type gas sensor of the present invention, Figure 10 FIG. shows a schematic diagram of the structure obtained after removing the sacrificial layer 16 in the preparation method of the thermal conductivity type gas sensor of the present invention.

[0114] As an example, the way to form the air vents 4 is a silicon deep reactive ion etching process, and the depth of the air vents 4 is determined according to the requirements of the structure, and no excessive limitation is made here.

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

[0116] As an example, after forming the air grooves 5, it further includes the steps of removing the sacrificial layer 16 and cleaning and drying the air grooves 5.

[0117] Please refer to Figure 11 again, and perform step S5: Provide a cover plate 3, and form a receiving groove 8 and a gas guide port 9 in the cover plate 3. The receiving groove 8 is opened on one side of the cover plate 3, and the gas guide port 9 penetrates the bottom of the receiving groove 8.

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

[0119] As an example, the way to form the receiving groove 8 and the gas guide port 9 includes wet etching, and the etching solution includes KOH.

[0120] Please refer to Figure 1, perform step S6: Align and join the side of the cover plate 3 with the receiving groove 8 and the side of the substrate 1 with the columnar fins 203, wherein the columnar fins 203 are located in the receiving groove 8, and the receiving groove 8 is connected to the air groove 5 through the vent hole 4.

[0121] As an example, the cover plate is joined to the substrate by a bonding technique. In this embodiment, a single-sided bonding technique is preferably used, which can simplify the preparation process and reduce the manufacturing cost.

[0122] As an example, the depth of the receiving groove 8 is greater than the height of the columnar fins 203 to ensure a certain spacing between the receiving groove 8 and the columnar fins 203. The depth of the receiving groove 8 can be determined according to the requirements of the structure and will not be limited here. The preparation method of the thermal conductivity gas sensor in this embodiment uses a silicon wafer with a (111) crystal orientation as the substrate and prepares a thermal conductivity gas sensor through a single-sided manufacturing and single-sided bonding process, which has the advantages of low manufacturing cost, good consistency, simple process, and meeting the requirements of miniaturization and integration.

[0123] Embodiment III

[0124] This embodiment provides a method for testing a thermal conductivity gas sensor, including the following steps:

[0125] Step 1: Provide any one of the thermal conductivity gas sensors described in Embodiment I and place the thermal conductivity gas sensor in a closed space of a background gas.

[0126] Step 2: Inject a sample gas into the closed space at different preset temperatures to calibrate the thermal conductivity gas sensor and obtain the required calibration relationship.

[0127] Step 3: Inject the gas to be measured into the closed space again and measure the voltage value of the thermal conductivity gas sensor at the preset temperature.

[0128] Step 4: Obtain the type and concentration of the gas to be measured according to the voltage value and the calibration relationship, wherein the type of the gas to be measured includes one or more.

[0129] Specifically, please refer to Figure 12 , which shows the working flow chart for calibration in the method for testing a thermal conductivity gas sensor of the present invention, including the following steps:

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

[0131] S1.2. At two temperatures T1 and T2, calibrate the response curves of sample gas Q1 and sample gas Q2 respectively, and calculate the response ratios at the two temperatures, denoted as K1 and K2. The specific operation is as follows:

[0132] (1) At temperature T1, inject sample gas Q1 and sample gas Q2 into the closed 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 closed 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 , obtain the ratio factor K1 = B T1 / B T2 of the sample gas Q2 and the ratio factor K2 = D T1 / D T2 .

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

[0136] (1) According to the voltage value B T1 and the voltage value D T1 , respectively fit the relationship between the concentration Z of nitrogen (i.e., the background gas) and the concentration A of the sample gas Q1 and the voltage value B T1 of the thermal conductivity gas sensor as B T1 = F(Z, A); the relationship between the concentration Z of nitrogen and the concentration C of the sample gas Q2 and the voltage value D T1 of the thermal conductivity gas sensor as D T1 = F(Z, C).

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

[0138] As an example, the background gas is different from the sample gas in type and does not undergo a chemical reaction. In other embodiments, other suitable gases can also be selected as the background gas, preferably an inert gas such as argon.

[0139] S1.4. Determine the weight factors corresponding to nitrogen and the sample gas, ignore the influence of mixing on thermal conductivity, and fit the calibration relational expression between the voltage value and the respective concentrations of nitrogen and the sample gas. The specific operation is as follows:

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

[0141] Specifically, please refer to Figure 13 , which shows the working flow chart for testing the concentration of the gas to be measured in the testing method of the thermal conductivity gas sensor of the present invention, including the following steps:

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

[0143] S1.2. Measure the gas to be measured at two temperatures T1 and T2 respectively, and calculate the K value at this time. The specific operation is as follows:

[0144] (1) Measure the voltage values V T1 and V T2 of the thermal conductivity gas sensor at temperatures T1 and T2 respectively.

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

[0146] S1.3. Judge the K value, and select different calibration relational expressions to obtain the type and concentration of the gas to be measured. The specific operation is as follows:

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

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

[0149] (2) When K = K2, it is determined that the gas to be measured is Q2, and according to the relational expression D T1 = F(Z, C) or D T2 = F(Z,

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

[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 according to the relational expression V = F(Z, A, C), the ternary gas concentration is obtained, i.e., the concentrations of the nitrogen gas (i.e., the background gas), the gas Q1 and the gas Q2 respectively.

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

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

[0154] In summary, the present invention provides a preparation method and a testing method for a thermal conductivity type gas sensor. The thermal conductivity type gas sensor includes a substrate, a support layer, a detection component, a cover plate and a ventilation port. Among them, an air groove is formed on one side of the substrate, the support layer is located on the side of the substrate with the air groove and includes a support suspension layer suspended above the air groove, the detection component is located on the support suspension layer and includes a heating coil, a protective layer and columnar fins arranged in sequence from bottom to top, the cover plate is located above the support layer, and a receiving groove is provided on the side of the cover plate facing the support layer. The detection component is located in the opening area of the receiving groove, a gas guiding port is provided at the bottom of the receiving groove, and the ventilation port is located on both sides of the heating coil and penetrates through the protective layer and the support suspension layer. The thermal conductivity type gas sensor of the present invention can shield the airflow interference, improve the response speed, and meet the requirements of miniaturization and integration. And the testing method of the thermal conductivity type gas sensor of the present invention uses this thermal conductivity type gas sensor. Through the preset formula, different gases to be measured can be accurately distinguished. Therefore, the present invention effectively overcomes various shortcomings in the prior art and has high industrial utilization value.

[0155] The above embodiments are only illustrative of the principles and effects of the present invention and are not intended to limit the present invention. Any person familiar with this technology can modify or change the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or changes made by those with ordinary knowledge in the technical field without departing from the spirit and technical idea disclosed by the present invention should still be covered by the claims of the present invention.

Claims

1. A thermal conductivity gas sensor, characterized in that: include: A substrate, wherein one side of the substrate is provided with an air groove; A support layer, located on a side of the substrate having the air groove, the support layer comprising a support suspension layer suspended above the air groove; A detection component is located on the supporting suspended layer, and the detection component includes a heating coil, a protective layer and a columnar fin. The heating coil is located on the surface of the supporting suspended layer, the protective layer is located on the surface of the supporting suspended layer and covers the heating coil, and the columnar fin is located on the protective layer; A cover plate is located above the support layer, a receiving groove is provided on one side of the cover plate facing the support layer, the detection assembly is located in the opening area of ​​the receiving groove, and an air guide port is provided at the bottom of the receiving groove to connect the receiving groove with the outside; The vents are located on both sides of the heating coil and penetrate the protective layer and the supporting suspended layer, and are used to connect the containing groove and the air groove.

2. The thermal conductivity gas sensor according to claim 1, characterized in that: The support layer is a composite layer, and the composite layer includes a silicon oxide layer and a silicon nitride layer.

3. The thermal conductivity gas sensor according to claim 1, characterized in that: An environmental resistor is also arranged on the supporting layer, and the environmental resistor is located around the supporting suspended layer, and an opening for exposing the environmental resistor is opened in the cover plate.

4. The thermal conductivity gas sensor according to claim 1, characterized in that: The heating coil extends back and forth on the supporting suspended layer in a zigzag manner.

5. The thermal conductivity gas sensor according to claim 1, characterized in that: The cross section of the columnar fin includes any one of a circular, rectangular and elliptical shape.

6. The thermal conductivity gas sensor according to claim 1, characterized in that: The top surface of the columnar fin is connected with heat sinks around four sides, and the top surface of the columnar fin is also provided with a groove.

7. The thermal conductivity gas sensor according to claim 1, characterized in that: 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 thermal conductivity coefficient.

8. A method for preparing a thermal conductivity gas sensor, characterized in that: The following steps are involved: Providing a substrate, and forming a support layer on one side of the substrate; forming a metal layer on the support layer, and patterning the metal layer to form a heating coil; forming a protective layer covering the heating coil on the support layer, and forming columnar fins on the protective layer; forming vents located on both sides of the heating coil in the protective layer and the supporting layer, and selectively etching the substrate based on the vents to obtain air grooves; Providing a cover plate, forming a receiving groove and an air guide port in the cover plate, wherein the receiving groove is opened on one side of the cover plate, and the air guide port passes through the bottom of the receiving groove; The side of the cover plate provided with the receiving groove and the side of the substrate provided with the columnar fin are aligned and connected to each other, wherein the columnar fin is located in the receiving groove, and the receiving groove is connected with the air groove through the vent.

9. A method for testing a thermal conductivity gas sensor, characterized in that: The following steps are involved: Providing a thermal conductivity gas sensor as claimed in any one of claims 1 to 7, and placing the thermal conductivity gas sensor in a background gas closed space; Injecting sample gas into the enclosed space at different preset temperatures to calibrate the thermal conductivity gas sensor to obtain a required calibration relationship; Then, injecting the gas to be tested into the enclosed space, and measuring the voltage value of the thermal conductivity gas sensor at the preset temperature; The type and concentration of the gas to be measured are obtained according to the voltage value and the calibration relationship, wherein the type of the gas to be measured includes one or more types.

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