Thermal conductivity gas sensor, and preparation method and test method therefor

Abstract

A thermal conductivity gas sensor, and a preparation method and a test method therefor. The thermal conductivity gas sensor comprises a substrate (1), a support layer (6), a detection assembly (2), a cover plate (3), and ventilation ports (4), wherein an air groove (5) is provided 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) and comprises a support suspended layer (7) suspended above the air groove (5); the detection assembly (2) is located on the support suspended layer (7) and comprises a heating coil (201), a protective layer (202) and a columnar fin (203), which are arranged in sequence from bottom to top; the cover plate (3) is located above the support layer (6), and the cover plate (3) is provided with an accommodating groove (8) on the side thereof facing the support layer (6); the detection assembly (2) is located in an opening region of the accommodating groove (8); a gas guide port (9) is provided at the bottom of the accommodating groove (8); and the ventilation ports (4) are located on two sides of the heating coil (201) and run through the protective layer (202) and the support suspended layer (7). The thermal conductivity gas sensor can shield against gas flow interference, improve the response speed, and meet the requirements of miniaturization and integration.

Description

A thermally conductive gas sensor and its fabrication and testing methods Technical Field

[0001] This invention belongs to the field of silicon microelectromechanical technology, and relates to a thermally conductive gas sensor and its preparation and testing methods. Background Technology

[0002] With the continuous development of MEMS technology, thermal conductivity gas sensors manufactured based on MEMS technology have been widely used in various fields. Thermal conductivity gas sensors achieve accurate measurement of gas type or concentration by detecting differences in gas thermal conductivity. Thanks to the high precision and high integration of MEMS processes, sensors manufactured using MEMS technology have further achieved advantages such as miniaturization, low power consumption, high sensitivity, and large-scale mass production compared to traditional technologies. Thermal conductivity gas sensors can provide higher performance at a lower cost, making them particularly suitable for gas monitoring applications in smart terminals, portable instruments, and the Internet of Things (IoT).

[0003] Common MEMS thermal conductivity gas sensors employ a suspended membrane formed through a release process. This membrane consists of a support layer, a metal coil, and a protective layer, forming a typical "sandwich" structure. This membrane exchanges heat with the measurement environment, enabling highly sensitive detection of differences in gas thermal conductivity. However, changes in airflow can affect the heat transfer process around the sensor's heating element, disrupting the sensor's thermal equilibrium and temperature distribution, leading to measurement signal fluctuations and impacting the sensor's accuracy and stability. Some studies have attempted to shield against airflow interference using external encapsulation, but such methods are difficult to meet the demands of mass production and limit device miniaturization. Based on MEMS technology, researchers have shielded against airflow interference by simultaneously encapsulating gas channels on both the front and back of the gas sensor. However, this method typically relies on back-side release and double-sided bonding processes, which are complex and costly, hindering large-scale application and making it difficult to achieve millisecond-level response times. Existing thermal conductivity hydrogen sensors typically have response times between 1 and 20 seconds, which may be insufficient for timely warnings in high-risk scenarios, making it difficult to effectively address potential hazards. Meanwhile, thermal conductivity gas sensors also suffer from a lack of gas selectivity during detection, making it difficult to accurately distinguish between different gases. To improve the response time of thermal conductivity gas sensors, optimization of the device is often employed. Regarding selectivity, common methods include combining the sensor with other types of sensors or using algorithms to compensate for airflow interference, thus mitigating this limitation. However, combining sensors with other types restricts device miniaturization and integration, and significantly increases operating costs. Algorithms for compensating for airflow interference are also complex to implement, further increasing system design and manufacturing costs.

[0004] Therefore, how to provide a thermally conductive gas sensor and its preparation and testing methods to shield against airflow interference, meet the requirements of miniaturization and integration, and solve the problems of slow response speed and inability to distinguish different gases in thermally conductive gas sensors has become an important problem that urgently needs to be solved by those skilled in the art.

[0005] It should be noted that the above introduction to the technical background is only for the purpose of providing a clear and complete explanation of the technical solutions of this application and facilitating understanding by those skilled in the art. It should not be assumed that these technical solutions are known to those skilled in the art simply because they have been described in the background section of this application. Summary of the Invention

[0006] In view of the shortcomings of the prior art described above, the purpose of this invention is to provide a thermally conductive gas sensor and its preparation and testing methods, in order to solve the problems that the thermally conductive gas sensor in the prior art is difficult to meet the requirements of miniaturization and integration, and has a slow response speed and cannot distinguish between different gases.

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

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

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

[0010] A detection component is located on the supporting suspended layer. The detection component includes a heating coil, a protective layer, and columnar fins. 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. The columnar fins are located on the protective layer.

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

[0012] The vent is located on both sides of the heating coil and extends through the protective layer and the supporting suspension layer, serving to connect the receiving groove and the air groove.

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

[0014] Optionally, the support layer is further provided with an environmental resistor, which is located around the support suspension layer, and the cover plate has an opening to expose the environmental resistor.

[0015] Optionally, the metal coil extends in a zigzag pattern on the supporting suspended layer.

[0016] Optionally, the cross-section of the columnar fin includes any one of circular, rectangular, and elliptical shapes.

[0017] Optionally, heat dissipation fins are connected around the top surface of the columnar fins, and grooves are also provided on the top surface of the columnar fins.

[0018] Optionally, both the protective layer and the columnar fins are provided with a thermally conductive layer, which includes nanomaterials with high thermal conductivity.

[0019] This invention also provides a method for preparing a thermally conductive gas sensor, comprising the following steps:

[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 protective layer covering the heating coil is formed on the support layer, and columnar fins are formed on the protective layer;

[0023] Vents are formed on both sides of the heating coil in the protective layer and the support layer, and the substrate is selectively etched based on the vents to obtain air grooves;

[0024] A cover plate is provided, forming a receiving groove and an air guide in the cover plate, the receiving groove being formed on one side of the cover plate, and the air guide penetrating the bottom of the receiving groove;

[0025] The side of the cover plate with the receiving groove is aligned and connected with the side of the substrate with the columnar fins, wherein the columnar fins are located in the receiving groove, and the receiving groove is connected to the air groove through the vent.

[0026] This invention also provides a testing method for a thermal conductivity gas sensor, comprising the following steps:

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

[0028] Sample gas was injected into the sealed space at different preset temperatures to calibrate the thermal conductivity gas sensor and obtain the required calibration formula.

[0029] The gas to be tested is then injected into the sealed space, and the voltage value of the thermal conductivity gas sensor at the preset temperature is measured.

[0030] The type and concentration of the gas to be tested are determined based on the voltage value and the calibration formula, wherein the type of the gas to be tested includes one or more.

[0031] As described above, this invention provides a thermally conductive gas sensor, its fabrication method, and a testing method. The thermally conductive gas sensor includes a substrate, a support layer, a detection component, a cover plate, and a vent. 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 sequentially from bottom to top. The cover plate is located above the support layer, and a receiving groove is formed on the side of the cover plate facing the support layer. The detection component is located within the opening area of ​​the receiving groove. A gas vent is provided at the bottom of the receiving groove. The vent is located on both sides of the heating coil and penetrates the protective layer and the support suspension layer. The thermally conductive gas sensor of this invention can shield against airflow interference, improve response speed, and meet the requirements of miniaturization and integration. Furthermore, the testing method of this thermally conductive gas sensor uses this sensor and, through a preset formula, can accurately distinguish different analytes. Attached Figure Description

[0032] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0033] Figure 1 shows a schematic diagram of a thermally conductive gas sensor according to the present invention.

[0034] Figure 2 shows a top view of another structure of the thermally conductive gas sensor of the present invention.

[0035] Figure 3 shows a process flow diagram of the fabrication method of the thermally conductive gas sensor of the present invention.

[0036] Figure 4 shows a schematic diagram of the structure obtained after providing a substrate and forming a support layer in the fabrication method of the thermally conductive gas sensor of the present invention.

[0037] Figure 5 shows a schematic diagram of the structure obtained after forming the metal coil and the ambient resistance in the preparation method of the thermally conductive gas sensor of the present invention.

[0038] Figure 6 shows a schematic diagram of the structure obtained after forming the protective layer and columnar fins in the preparation method of the thermally conductive gas sensor of the present invention.

[0039] Figure 7 shows a schematic diagram of the structure obtained after forming the sacrificial layer in the fabrication method of the thermally conductive gas sensor of the present invention.

[0040] Figure 8 shows a schematic diagram of the structure obtained after forming the filling layer in the preparation method of the thermally conductive gas sensor of the present invention.

[0041] Figure 9 shows a schematic diagram of the structure obtained after forming the vent in the preparation method of the thermally conductive gas sensor of the present invention.

[0042] Figure 10 shows a schematic diagram of the structure obtained after removing the sacrificial layer in the preparation method of the thermally conductive gas sensor of the present invention.

[0043] Figure 11 shows a schematic diagram of the structure of the cover plate provided in the method for preparing the thermally conductive gas sensor of the present invention.

[0044] Figure 12 shows a flowchart of the calibration process in the thermal conductivity gas sensor testing method of the present invention.

[0045] Figure 13 shows a flowchart of the process for testing the concentration of the gas to be tested in the thermal conductivity gas sensor test method of the present invention.

[0046] Figure Reference Numerals: 1. Substrate; 2. Probe Component; 201. Heating Coil; 202. Protective Layer; 203. Columnar Fin; 3. Cover Plate; 4. Vent; 5. Air Recess; 6. Support Layer; 7. Support Suspension Layer; 8. Receiving Groove; 9. Air Channel; 10. Ambient Resistance; 11. Opening; 12. Lead-out Pad; 13. Second Opening; 14. Heat Sink; 15. Groove; 16. Sacrificial Layer; 17. Filler Layer; 18. Thermal Conductive Layer; S1-S6. Steps Detailed Implementation

[0047] The following specific examples illustrate the implementation of the present invention. 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 embodiments, and 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.

[0048] It should be emphasized that the term "including / comprises" as used herein refers to the presence of a feature, whole, step, or component, but does not exclude the presence or addition of one or more other features, wholes, steps, or components.

[0049] Features described and / or illustrated for one embodiment may be used in the same or similar manner in one or more other embodiments, combined with features in other embodiments, or substituted for features in other embodiments.

[0050] In the detailed description of embodiments of the present invention, for ease of explanation, the schematic diagrams of the device may be partially enlarged without adhering to the general scale, and the schematic diagrams are merely examples and should not limit the scope of protection of the present invention. Furthermore, in actual manufacturing, the three-dimensional spatial dimensions of length, width, and depth should be included.

[0051] For ease of description, spatial relation terms such as “below,” “under,” “lower than,” “below,” “above,” and “upper” may be used herein to describe the relationship between one element or feature shown in the accompanying drawings and other elements or features. It will be understood that these spatial relation terms are intended to include directions other than those depicted in the drawings for devices in use or operation. Furthermore, when a layer is referred to as being “between” two layers, it may be the only layer between the two layers, or there may be one or more layers in between.

[0052] In the context of this application, the description of the first feature "above" the second feature may include embodiments in which the first and second features are in direct contact, or embodiments in which additional features are formed between the first and second features, such that the first and second features may not be in direct contact.

[0053] It should be noted that the illustrations provided in this embodiment are only schematic representations of the basic concept of the present invention. Therefore, the illustrations only show the components related to the present invention and are not drawn according to the actual number, shape and size of the components in the actual implementation. In the actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0054] Example 1

[0055] This embodiment provides a thermal conductivity gas sensor. Referring to Figure 1, which shows a schematic diagram of one structure of the thermal conductivity gas sensor of the present invention, it includes a substrate 1, a support layer 6, a detection component 2, a cover plate 3, and a vent 4. An air groove 5 is formed on one side of the substrate 1. The support layer 6 is located on the side of the substrate 1 with 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 support suspension layer. 7. The protective layer 202 is located on the surface 7 of the supporting suspended layer 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 side of the cover plate 3 facing the supporting layer 6 is provided with a receiving groove 8. The detection component 2 is located in the opening area of ​​the receiving groove 8. The bottom of the receiving groove 8 is provided with an air guide port 9 to allow the receiving groove 8 to communicate with the outside. The air vent 4 is located on both sides of the heating coil 201 and penetrates the protective layer 202 and the supporting suspended layer 7, and is used to connect the receiving groove 8 with the air groove 5.

[0056] Specifically, when the thermal conductivity gas sensor is working, the gas to be measured enters the receiving groove 8 through the gas inlet 9. The resistance of the heating coil 201 changes. By converting the resistance change into an electrical signal, the thermal conductivity gas sensor can quantitatively measure the gas concentration. The air groove 5, located below the supporting suspended layer 7, effectively utilizes the low thermal conductivity of air for insulation. The columnar fins 203, located between the protective layer 202 and the cover plate 3, effectively increase the heat dissipation area of ​​the heating coil 201, accelerate heat exchange between the columnar fins 203 and the surrounding gas, and also provide turbulence, reducing the thickness of the surface thermal boundary layer of the heating coil 201, reducing the heat conduction distance, and thus improving the response speed of the thermal conductivity gas sensor.

[0057] Specifically, the cover plate 3 with the air inlet 9 provides a gas flow channel, which can effectively reduce gas flow interference and avoid the influence of airflow changes on the measurement signal of the thermal conductivity gas sensor. This further improves the measurement accuracy of the thermal conductivity gas sensor, making it perform excellently in dynamic flow environments. It should also be noted that the air inlet 9 is hourglass-shaped, which is more conducive to the entry of external gas into the thermal conductivity gas sensor, improving its working efficiency. As an example, the support layer 6 is a composite layer, which includes a silicon oxide layer and a silicon nitride layer.

[0058] 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 ambient resistor 10 is also provided on the support layer 6, located around the support suspension layer 7. An opening 11 is provided in the cover plate 3 to expose the ambient resistor 10. The ambient resistor 10 is used to detect the temperature of the external environment when the heating coil 201 is working in real time. When the external temperature changes, the resistance value of the ambient resistor 10 also changes. Through reasonable circuit design, the interference effect caused by ambient temperature fluctuations can be compensated, realizing the compensation calculation of the measurement results of the heating coil 201, correcting the measurement results to ensure accurate measurement values, and ensuring that the heating coil 201 is always in optimal working condition. As an example, a lead-out pad 12 is also provided on the support layer 6, and a second opening 13 is provided in the cover plate 3 to expose the lead-out pad 12. The lead-out pad 12 is electrically connected to the ambient resistor 10 and the heating coil 201 respectively, for electrically leading out the thermal conductivity gas sensor.

[0059] As an example, please refer to Figure 2. A cross-sectional view along the AA' direction is shown in Figure 1. Region B in Figure 2 constitutes a thermal conductivity gas sensor of this embodiment, and region C constitutes a reference sensor. The cover plate of the reference sensor does not have a gas inlet. When the thermal conductivity gas sensor of this embodiment performs gas measurement, the reference sensor is located in the same background gas space and does not contact the gas to be measured. It is used to further provide compensation calculations and improve the accuracy of the measurement structure.

[0060] As an example, the metal coil extends in a zigzag pattern on the supporting suspended layer 7 to reduce the area occupied by the detection component 2, which is beneficial for device miniaturization. In other embodiments, the metal coil may also be in a U-shape; the shape of the metal coil can be determined according to specific circumstances, and no further restrictions are imposed here.

[0061] 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.

[0062] As an example, the cross-section of the columnar fin 203 includes any one of circular, rectangular, and elliptical shapes.

[0063] As an example, the thickness of the support layer 6 ranges from 100nm to 500nm, and the height of the columnar fins 203 ranges from 1000nm to 3000nm.

[0064] As an example, both the protective layer 202 and the columnar fins 203 are provided with a thermally conductive layer 18. The thermally conductive layer 18 is made of nanomaterials with high thermal conductivity, such as nanodiamond, carbon nanotubes, graphene and other nanomaterials. Through the high thermal conductivity characteristics of nanomaterials with high thermal conductivity, the heat transfer efficiency of convection and conduction can be effectively improved, and the sensitivity of the thermal conductivity gas sensor response can be further improved. It should be noted that, since nanomaterials with high thermal conductivity are difficult to prepare, other gas sensors do not use nanomaterials with high thermal conductivity.

[0065] The thermal conductivity gas sensor of this embodiment includes a substrate, an air groove, a support layer, a detection component, a cover plate, and a vent. The detection component includes a heating coil, a protective layer, and columnar fins. The cover plate has a receiving groove and a vent. The thermal conductivity gas sensor of this embodiment can shield against airflow interference through the cover plate. Utilizing the columnar fins and their turbulence-inducing effect, it can effectively improve the heat dissipation of the heating coil and reduce the thickness of its surface thermal boundary layer, thereby improving the response speed of the thermal conductivity gas sensor.

[0066] Example 2

[0067] This embodiment provides a method for fabricating a thermally conductive gas sensor. Please refer to Figure 3, which shows a process flow diagram of the fabrication method of the thermally conductive gas sensor of the present invention, including the following steps:

[0068] 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.

[0069] As an example, the substrate 1 is an N-type single-polished or double-polished single-crystal silicon substrate with (111) crystal plane, and the resistivity of the substrate 1 is 1Ω·cm to 10Ω·cm.

[0070] 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 tetraethoxysilane (TEOS)-silicon nitride (SiNx)-tetraethoxysilane (TEOS).

[0071] Referring again to Figure 5, perform step S2: form a metal layer on the support layer 6, and pattern the metal layer to form the heating coil 201.

[0072] As an example, the metal layer includes a Ta layer and a Pt layer located on the Ta, wherein 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.

[0073] As an example, the metal layer can be graphically represented by either an ion beam etching process or an ion beam stripping process.

[0074] As an example, the method also includes the step of etching the metal layer to form the ambient resistance 10. In this embodiment, the heating coil 201 and the ambient resistance 10 are patterned using the same metal layer.

[0075] Referring again to Figure 6, step S3 is performed: a protective layer 202 covering the heating coil 201 is formed on the support layer 6, and columnar fins 203 are formed on the protective layer 202.

[0076] As an example, the protective layer 202 is formed by plasma-enhanced chemical vapor deposition.

[0077] As an example, the thickness of the protective layer 202 ranges from 100nm to 500nm. In this embodiment, the protective layer 202 includes any one or a combination of silicon oxide and silicon nitride.

[0078] As an example, the protective layer 202 also has an opening 11 that exposes the ambient resistance 10.

[0079] As an example, forming the columnar fins 203 on the protective layer 202 includes the following steps:

[0080] (1) Referring 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.

[0081] (2) Referring again to Figure 8, a filling layer 17 is deposited on the sacrificial layer 16 and the growth holes are filled by plasma-enhanced chemical vapor deposition.

[0082] (3) Referring again 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, heat sinks 14 are connected around the top surface of the columnar fins 203, and grooves 15 are also formed on the top surface of the columnar fins 203. The presence of the heat sinks 14 and the grooves 15 can further enhance the turbulence effect of the heat dissipation element columnar fins 203, thereby effectively improving the response speed.

[0083] As an example, the sacrificial layer 16 includes any one or a combination of monocrystalline silicon and polycrystalline silicon, and the thickness of the sacrificial layer 16 ranges from 1000 nm to 3000 nm.

[0084] As an example, the filling layer 17 includes either silicon oxide or silicon nitride.

[0085] As an example, referring again to Figure 1, the method further includes the step of forming a thermally conductive layer 18 on the protective layer 202 and the columnar fins 203. The thermally conductive layer 18 is formed using a spotting technique, including the following steps:

[0086] (1) Preparation of nanomaterial dispersion: Dissolve an appropriate amount of nanoparticles with a dispersant and disperse them by ultrasonication to prepare the desired nanomaterial dispersion.

[0087] (2) Surface cleaning: The surface of the protective layer 202 and the columnar fins 203 are cleaned with plasma.

[0088] (3) Spotting and particle deposition: Using appropriate spotting parameters, uniform spotting is performed on the surface of the protective layer 202 and the columnar fins 203.

[0089] (4) Post-processing: Place the spotted structure in a clean environment for natural drying or use a low-temperature oven for rapid drying to avoid particle movement.

[0090] Specifically, high thermal conductivity nanomaterials are attached to the surface of the protective layer 202 and the columnar fins 203 using a spotting technique. The high thermal conductivity of the nanomaterials can greatly improve the heat transfer efficiency of convection and conduction, and enhance the response sensitivity.

[0091] Referring again to Figures 9 and 10, step S4 is performed: vents 4 are formed on both sides of the heating coil 201 in the protective layer 202 and the support layer 6; the substrate 1 is selectively etched based on the vents 4 to obtain air grooves 5. Figure 9 shows a schematic diagram of the structure obtained after forming the vents 4 in the fabrication method of the thermally conductive gas sensor of the present invention, and Figure 10 shows a schematic diagram of the structure obtained after removing the sacrificial layer 16 in the fabrication method of the thermally conductive gas sensor of the present invention.

[0092] As an example, the ventilation port 4 is formed by a silicon deep reactive ion etching process. The depth of the ventilation port 4 depends on the structural requirements and is not limited here.

[0093] As an example, the selective etching solution used includes either KOH or TMAH (tetramethylammonium hydroxide, 25%).

[0094] As an example, after the air groove 5 is formed, the steps of removing the sacrificial layer 16 and cleaning and drying the air groove 5 are also included.

[0095] Please refer to Figure 11 again. Step S5 is performed: a cover plate 3 is provided, forming a receiving groove 8 and an air guide 9 in the cover plate 3. The receiving groove 8 is opened on one side of the cover plate 3, and the air guide 9 penetrates the bottom of the receiving groove 8.

[0096] 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.

[0097] As an example, the method of forming the receiving groove 8 and the air inlet 9 includes wet etching, and the etching solution includes KOH.

[0098] Referring again to Figure 1, step S6 is performed: the side of the cover plate 3 with the receiving groove 8 is aligned with the side of the substrate 1 with the columnar fin 203 and connected to each other, wherein the columnar fin 203 is located in the receiving groove 8, and the receiving groove 8 is connected to the air groove 5 through the vent 4.

[0099] As an example, the cover plate is bonded to the substrate by bonding technology. In this embodiment, single-sided bonding technology is preferred, which can simplify the preparation process and reduce the manufacturing cost.

[0100] As an example, the depth of the receiving groove 8 is greater than the height of the columnar fin 203 to ensure a certain distance between the receiving groove 8 and the columnar fin 203. The depth of the receiving groove 8 can be determined according to structural requirements, and no further restrictions are imposed here. The fabrication method of the thermal conductivity gas sensor in this embodiment uses a (111) crystal orientation silicon wafer as a substrate and fabricates the thermal conductivity gas sensor through single-sided manufacturing and single-sided bonding processes. It has the advantages of low manufacturing cost, good consistency, simple process, and meeting the requirements of miniaturization and integration.

[0101] Example 3

[0102] This embodiment provides a testing method for a thermal conductivity gas sensor, including the following steps:

[0103] Step 1: Provide any of the thermal conductivity gas sensors described in Example 1, and place the thermal conductivity gas sensor in a closed space with background gas.

[0104] Step 2: Inject sample gas into the sealed space at different preset temperatures to calibrate the thermal conductivity gas sensor and obtain the required calibration formula.

[0105] Step 3: Inject the gas to be tested into the sealed space and measure the voltage value of the thermal conductivity gas sensor at the preset temperature.

[0106] Step 4: Determine the type and concentration of the gas to be tested based on the voltage value and the calibration formula, wherein the type of the gas to be tested includes one or more.

[0107] Specifically, please refer to Figure 12, which shows a flowchart of the calibration process in the thermal conductivity gas sensor testing method of the present invention, including the following steps:

[0108] S1.1. Calibration using nitrogen as the background gas.

[0109] S1.2. At temperatures T1 and T2, calibrate the response curves for 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:

[0110] (1) At temperature T1, sample gas Q1 and sample gas Q2 are injected into the sealed space respectively, and the voltage value B corresponding to sample gas Q1 is measured. T1 and the voltage value D corresponding to the sample gas Q2. T1 .

[0111] (2) At temperature T2, sample gas Q1 and sample gas Q2 are injected into the sealed space respectively, and the voltage value B corresponding to sample gas Q1 is measured. T2 and the voltage value D corresponding to the sample gas Q2. T2 .

[0112] (3) According to the voltage value B T1 and the voltage value B T2 The ratio factor K1 = B for the sample gas Q2 was obtained. T1 / B T2 The ratio factor K2 = D for the sample gas Q2. T1 / D T2 .

[0113] 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 as follows:

[0114] (1) According to the voltage value B T1 and the voltage value D T1 The concentration Z of nitrogen (i.e., background gas) and the concentration A of sample gas Q1 are respectively fitted to the voltage value B of the thermal conductivity gas sensor. T1 Relationship B T1 =F(Z, A); the concentration Z of nitrogen gas and the concentration C of sample gas Q2 are related to the voltage D of the thermal conductivity gas sensor. T1 Relationship D T1 =F(Z, C).

[0115] (2) According to the voltage value B T2 and the voltage value D T2 The concentrations Z of nitrogen gas and A of sample gas Q1 are respectively fitted to the voltage value B of the thermal conductivity gas sensor. T2 Relationship B T2 =F(Z, A); the concentration Z of nitrogen gas and the concentration C of sample gas Q2 are related to the voltage D of the thermal conductivity gas sensor. T2 The relation is DT2 = F(Z, C).

[0116] As an example, the background gas is of a different type from the sample gas and does not react chemically. In other embodiments, the background gas may also be other suitable gases, preferably inert gases, such as argon.

[0117] S1.4. Determine the weighting factors for nitrogen and sample gases, ignore the effect of mixing on thermal conductivity, and fit the calibration relationship between voltage value and the concentrations of nitrogen and sample gases. The specific steps are as follows:

[0118] According to relation 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 weighting factors corresponding to the nitrogen concentration Z, the sample gas Q1 concentration A, and the sample gas Q2 concentration C, and fit the relationship between the voltage value V of the thermal conductivity gas sensor and the nitrogen concentration Z, the sample gas Q1 concentration A, and the sample gas Q2 concentration C: V = F(Z,A,C).

[0119] Specifically, please refer to Figure 13, which shows the workflow of testing the concentration of the gas to be tested in the thermal conductivity gas sensor testing method of the present invention, including the following steps:

[0120] S1.1. Introduce the gas to be tested, that is, inject the gas to be tested into the sealed space.

[0121] S1.2. Measure the gas to be tested at two temperatures, T1 and T2, and calculate the K value at each temperature. The specific procedure is as follows:

[0122] (1) The voltage value V of the thermal conductivity gas sensor was measured at temperatures T1 and T2 respectively. T1 and V T2 .

[0123] (2) According to the voltage value V T1 and the voltage value V T2 The ratio factor K = V is obtained. T1 / V T2 .

[0124] S1.3. Determine the K value and use different calibration formulas to obtain the type and concentration of the gas to be measured. The specific operation is as follows:

[0125] (1) When K = K1, the gas to be tested is determined to be Q1, and according to the relationship B T1 =F(Z, A) or B T2 =F(Z,

[0126] A) Calculate the output binary gas concentration, that is, the concentration of nitrogen (i.e., background gas) and the gas to be measured Q1.

[0127] (2) When K = K2, the gas to be tested is determined to be Q2, and according to the relationship D T1 =F(Z, C) or D T2 =F(Z,

[0128] C) Calculate the concentration of the binary gas, namely the concentration of the nitrogen (i.e., the background gas) and the gas to be measured, Q2.

[0129] (3) When K≠K1 and K≠K2, it is determined that the gas to be tested is a mixture of gas Q1 and gas Q2, and the concentration of the ternary gas is obtained according to the relationship V=F(Z,A,C), that is, the concentration of nitrogen (i.e. background gas), gas Q1 and gas Q2 respectively.

[0130] As an example, sample gas Q1 is hydrogen and sample gas Q2 is carbon monoxide. In other embodiments, sample gas Q1 and sample gas Q2 may be other gases. It should be noted that the sample gas and the background gas will not react chemically, and when sample gas Q1 and sample gas Q2 are mixed for testing, no chemical reaction will occur between the sample gases.

[0131] The testing method for the thermal conductivity gas sensor in this embodiment can identify the type and composition of gases by testing at multiple temperatures.

[0132] In summary, this invention provides a thermal conductivity gas sensor, its fabrication method, and its testing method. The thermal conductivity gas sensor includes a substrate, a support layer, a detection component, a cover plate, and a vent. One side of the substrate has an air groove. 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 sequentially from bottom to top. The cover plate is located above the support layer, and the side of the cover plate facing the support layer has a receiving groove. The detection component is located within the opening area of ​​the receiving groove. A vent is located at the bottom of the receiving groove. The vent is located on both sides of the heating coil and penetrates the protective layer and the support suspension layer. The thermal conductivity gas sensor of this invention can shield against airflow interference, improve response speed, and meet the requirements of miniaturization and integration. Furthermore, the testing method of this thermal conductivity gas sensor, using a preset formula, can accurately distinguish different analytes. Therefore, this invention effectively overcomes the various shortcomings of the prior art and has high industrial applicability.

[0133] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in 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 an air groove is formed on one side of the substrate; A support layer is located on the side of the substrate having the air groove, the support layer including a support suspension layer suspended above the air groove; A detection component is located on the supporting suspended layer. The detection component includes a heating coil, a protective layer, and columnar fins. 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. The columnar fins are located on the protective layer. A cover plate is located above the support layer. The side of the cover plate facing the support layer is provided with a receiving groove. The detection component is located in the opening area of ​​the receiving groove. The bottom of the receiving groove is provided with an air guide port to allow the receiving groove to communicate with the outside. The vent is located on both sides of the heating coil and extends through the protective layer and the supporting suspension layer, serving to connect the receiving 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, which 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 provided on the support layer. The environmental resistor is located around the support suspension layer, and an opening is provided in the cover plate to expose the environmental resistor.

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

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

6. The thermal conductivity gas sensor according to claim 1, characterized in that: The top surface of the columnar fins is connected to heat dissipation fins around its perimeter, and the top surface of the columnar fins is also provided with grooves.

7. The thermal conductivity gas sensor according to claim 1, characterized in that: Both the protective layer and the columnar fins are provided with a thermally conductive layer, which includes nanomaterials with high thermal conductivity.

8. A method for fabricating a thermally conductive gas sensor, characterized in that, Includes the following steps: A substrate is provided, and a support layer is formed on one side of the substrate; A metal layer is formed on the support layer, and the metal layer is patterned to form a heating coil; A protective layer covering the heating coil is formed on the support layer, and columnar fins are formed on the protective layer; Vents are formed on both sides of the heating coil in the protective layer and the support layer, and the substrate is selectively etched based on the vents to obtain air grooves; A cover plate is provided, forming a receiving groove and an air guide in the cover plate, the receiving groove being formed on one side of the cover plate, and the air guide penetrating the bottom of the receiving groove; The side of the cover plate with the receiving groove is aligned and connected with the side of the substrate with the columnar fins, wherein the columnar fins are located in the receiving groove, and the receiving groove is connected to the air groove through the vent.

9. A testing method for a thermal conductivity gas sensor, characterized in that, Includes the following steps: Provide a thermally conductive gas sensor as described in any one of claims 1-7, wherein the thermally conductive gas sensor is placed in a background gas-sealed space; Sample gas was injected into the sealed space at different preset temperatures to calibrate the thermal conductivity gas sensor and obtain the required calibration formula. The gas to be tested is then injected into the sealed space, and the voltage value of the thermal conductivity gas sensor at the preset temperature is measured. The type and concentration of the gas to be tested are determined based on the voltage value and the calibration formula, wherein the type of the gas to be tested includes one or more.

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