MEMS micro-hot plate gas sensor with thermal magnetic temperature measurement structure and preparation method thereof

Abstract

The invention provides a MEMS micro-hotplate gas sensor with a thermomagnetic temperature measurement structure and a preparation method thereof, which relate to the field of sensors; the sensor comprises a substrate and a diaphragm structure arranged above the substrate; the diaphragm structure comprises a passivation layer, a heating electrode, a permanent magnetic film layer, a first heat transfer insulation layer, a heat detection electrode, a second heat transfer insulation layer, a gas detection electrode and a gas sensitive film which are stacked from bottom to top; when working, the heating electrode is used as a heat source and is transmitted to the sensing area and the gas sensitive film respectively; the gas sensitive film receives the heat flow and is heated to the working temperature range to react with the gas to be measured, and then changes its resistance, which is converted into the concentration of the gas to be measured after being detected by the gas detection electrode; the permanent magnetic film layer generates a magnetic field when working, and the heat detection electrode converts the reaction temperature change of the gas sensitive film into the output voltage change based on the Nernstow effect, so as to realize real-time monitoring of the reaction temperature of the gas sensitive film.

Description

Technical Field

[0001] The present invention relates to the technical field of sensors, and in particular to a MEMS micro-hot plate type gas sensor with a thermal magnetic temperature measurement structure and a preparation method thereof. Background Art

[0002] With the development of society, more and more scenes in social life need to measure the concentration of various gases in real time. The principle of MEMS micro-hotplate gas sensor is to use the reaction between gas and gas-sensitive film to change the electrical properties of the gas-sensitive film, so as to know the concentration of the gas to be measured. The micro-hotplate is used to heat the gas-sensitive film to improve the reaction speed and conversion rate. In addition, MEMS micro-hotplate gas sensor is gradually favored due to its miniaturization, low cost, high reliability, easy integration and other advantages.

[0003] For MEMS micro-hotplate gas sensors, as the temperature rises, the reaction degree between the gas-sensitive film and the gas to be measured increases first and then decreases. In order to achieve higher accuracy and sensitivity, the gas-sensitive film of the micro-hotplate gas sensor needs to be controlled at an appropriate temperature to achieve the maximum reaction degree. Therefore, it is necessary to detect and control the temperature of the gas sensor. The traditional temperature measurement method of the micro-hotplate gas sensor is to use a probe to contact the area to be measured and measure using the principle of thermocouple or thermal resistor. However, due to the small size of the MEMS micro-hotplate gas sensor, which is even smaller than the probe size, the temperature measurement is inaccurate. At the same time, these traditional contact measurements will bring about changes in the temperature distribution of the sensor and a decrease in the heat transfer efficiency of the micro-hotplate. In addition, since the gas-sensitive film needs to be in contact with the gas to be measured, and the existing temperature measurement structure needs to touch the gas-sensitive film for measurement, if the contact is long-term, it will occupy the area of ​​the reaction interface between the gas-sensitive film and the gas to be measured, resulting in a decrease in reaction efficiency. Short-term contact cannot dynamically monitor the reaction temperature of the gas sensor in real time. Summary of the invention

[0004] The purpose of the present invention is to provide a MEMS micro-hotplate gas sensor with a thermal magnetic temperature measurement structure and a preparation method thereof, which can achieve accurate and real-time measurement of the reaction temperature of the gas to be measured and the gas sensitive film, and further improve the accuracy and sensitivity of the MEMS micro-hotplate gas sensor.

[0005] To achieve the above object, the present invention proposes the following technical solutions:

[0006] In a first aspect, a MEMS micro-hotplate gas sensor with a thermal magnetic temperature measurement structure is disclosed, comprising a substrate and a diaphragm structure arranged above the substrate;

[0007] The diaphragm structure includes a passivation layer, a heating electrode, a permanent magnetic film layer, a first heat transfer insulation layer, a heat detection electrode, a second heat transfer insulation layer, a gas detection electrode and a gas sensitive film stacked from bottom to top; the heating electrode is used as a heat source, and the heat flow generated by it is transmitted to the sensing area through the passivation layer in one way, and the other heat flow is transmitted to the gas sensitive film through the first heat transfer insulation layer, the heat detection electrode and the second heat transfer insulation layer; the gas sensitive film receives the heat flow and heats up to the working temperature range, reacts chemically with the gas to be measured, and changes its own resistance, which is detected by the gas detection electrode and converted into the concentration of the gas to be measured; the permanent magnetic film layer generates a magnetic field when the MEMS micro-hot plate gas sensor is in a working state, and the heat detection electrode converts the reaction temperature change of the gas sensitive film into an output voltage change based on the Nernst effect, thereby realizing real-time monitoring of the reaction temperature of the gas sensitive film.

[0008] Furthermore, the passivation layer is arranged on the substrate, the middle part of the passivation layer is horizontally arranged as a cross structure, and the outer periphery of the passivation layer is arranged as a frame for supporting the cross structure;

[0009] The heating electrode is fixed on the upper surface of the passivation layer, and its plane structure corresponds to the two horizontal arms and the central position of the cross structure; the shape of the partial plane structure of the heating electrode corresponding to the center of the cross structure is set to a serpentine structure, and the crests and troughs of the serpentine structure extend toward the two longitudinal arms of the cross structure.

[0010] Furthermore, the diaphragm structure also includes a first heat-insulating layer;

[0011] The first heat-insulating layer is located on the upper surface of the passivation layer and around the heating electrode, its upper surface is flush with the upper surface of the heating electrode, and its portion located around the heating electrode fully fills the gaps in the serpentine structure.

[0012] Furthermore, the permanent magnetic film layer is arranged on the upper surface of the heating electrode and the first thermal insulation layer, and its planar structure corresponds to above the four extension arms of the cross structure; the permanent magnetic film layer is composed of FePt, CoPt, CoNiMnP or Sr ferrite, and has a thickness of 1 to 5um.

[0013] Furthermore, the upper surface of the first heat transfer insulation layer is horizontal, and its bottom is arranged on the upper surfaces of the heating electrode, the first heat insulation layer and the permanent magnetic film layer; the thickness of the first heat transfer insulation layer is 2.1~2.2um, and its planar structure corresponds to the cross structure; the first heat transfer insulation layer is used to generate horizontal heat flow while transferring heat.

[0014] Furthermore, the heat detection electrode is disposed on the upper surface of the first heat transfer insulation layer; the plane structure of the heat detection electrode corresponds to the cross structure;

[0015] The ends of the four extension arms on the planar structure of the thermal detection electrode are respectively provided with electrode lead-out spaces for the heating electrodes;

[0016] The permanent magnetic film layer is used to generate a magnetic field perpendicular to the heat detection electrode. There is a heat flow on the heat detection electrode that is transmitted along the center of the heat detection electrode to the four arms of the cross structure. Based on the Nernstow effect, an electromotive force is generated on both sides of the heat detection electrode that are perpendicular to the heat flow direction.

[0017] The first heat transfer insulating layer is used to electrically isolate the heating electrode from the heat detection electrode.

[0018] Furthermore, the upper surface of the second heat transfer insulation layer is horizontal, and its bottom is arranged on the upper surface of the first heat transfer insulation layer and the thermal detection electrode; the thickness of the second heat transfer insulation layer is 100 to 300 nm, and its plane structure corresponds to the cross structure.

[0019] Furthermore, the gas detection electrode is fixedly arranged on the upper surface of the second heat transfer insulating layer, and its plane structure corresponds to the longitudinal two arms and the central position of the cross structure; the shape of the partial plane structure of the gas detection electrode corresponding to the central part of the cross structure is set as a comb tooth structure, and the comb tooth structure is staggered along the two lateral arms of the cross structure, and is used to detect the electrical quantity of different areas of the gas sensitive film;

[0020] The gas-sensitive film is located above the gas detection electrode, and its plane structure corresponds to the gas detection electrode;

[0021] The second heat transfer insulating layer is used to electrically isolate the heat detection electrode from the gas detection electrode.

[0022] Furthermore, the diaphragm structure also includes a second heat-insulating layer;

[0023] The second thermal insulation layer is located on the first thermal insulation layer and the second heat transfer insulation layer, and its upper surface is flush with the upper surface of the gas sensitive film, and the planar structure of the second thermal insulation layer corresponds to the frame and the cross structure; the second thermal insulation layer is used to form electrical isolation between the heating electrode, the heat detection electrode, and the gas detection electrode, and is used to simultaneously form heat isolation between the second heat transfer insulation layer and the outside world.

[0024] Furthermore, the diaphragm structure further includes a first lead, a second lead and a third lead;

[0025] The first lead is located in the first heat-insulating layer and the second heat-insulating layer, and is electrically connected to the heating electrode. The thickness of the first lead is the distance from the bottom surface of the heating electrode to the upper surface of the diaphragm structure.

[0026] The second lead is located in the second heat-insulating layer and is electrically connected to the heat detection electrode. The thickness of the second lead is the distance from the bottom surface of the heat detection electrode to the upper surface of the diaphragm structure.

[0027] The third lead is located in the second heat-insulating layer and is electrically connected to the gas detection electrode. The thickness of the third lead is the distance from the bottom surface of the gas detection electrode to the upper surface of the diaphragm structure.

[0028] Further, the passivation layer includes a first passivation layer and a second passivation layer;

[0029] The first passivation layer is located on the upper surface of the substrate, and its planar structure includes the cross structure located in the middle and a frame supporting the cross structure; the material of the first passivation layer is silicon nitride, and the thickness is 100-500nm;

[0030] The second passivation layer is located on the upper surface of the first passivation layer, and its planar structure corresponds to the planar structure of the first passivation layer; the material of the second passivation layer is silicon dioxide, and the thickness is 100-500nm.

[0031] In a second aspect, a method for preparing the above-mentioned MEMS micro-hotplate gas sensor with a thermal magnetic temperature measurement structure is disclosed, and the method comprises the following steps:

[0032] 1) A silicon wafer is selected as a substrate, the upper surface of the substrate is horizontal, the middle of the substrate is divided into a sensing area of ​​a cross structure, the periphery of the sensing area is divided into a supporting area, and the supporting area is set as a frame for supporting the cross structure;

[0033] 2) sequentially preparing a first passivation layer and a second passivation layer on the upper surfaces of the support area and the sensing area by photolithography and low pressure chemical vapor deposition;

[0034] 3) preparing a first metal layer and a second metal layer on the upper surface of the second passivation layer by photolithography and magnetron sputtering, as a first adhesion area and a heating electrode, that is, the heating electrode is fixedly arranged on the upper surface of the second passivation layer through the first adhesion area;

[0035] 4) preparing a first heat-insulating layer on the upper surface of the second passivation layer and around the heating electrode by photolithography and low-pressure chemical vapor deposition;

[0036] 5) preparing an alloy layer as a permanent magnetic film layer on the upper surface of the heating electrode and the first thermal insulation layer by photolithography and magnetron sputtering;

[0037] 6) preparing a first heat transfer insulation layer on the upper surface of the heating electrode, the first heat insulation layer, and the permanent magnetic film layer by photolithography and plasma enhanced chemical vapor deposition;

[0038] 7) preparing a third metal layer on the upper surface of the first heat transfer insulating layer by photolithography and magnetron sputtering to serve as a heat detection electrode;

[0039] 8) preparing a second heat transfer insulation layer on the upper surface of the first heat transfer insulation layer and the heat detection electrode by photolithography and plasma enhanced chemical vapor deposition;

[0040] 9) preparing a fourth metal layer and a fifth metal layer on the upper surface of the second heat transfer insulating layer by photolithography and magnetron sputtering, as the second adhesion area and the gas detection electrode, that is, the gas detection electrode is fixed on the upper surface of the second heat transfer insulating layer through the second adhesion area;

[0041] 10) preparing a gas-sensitive film on the upper surface of the gas detection electrode by photolithography and spin coating;

[0042] 11) preparing a second thermal insulation layer on the first thermal insulation layer, the upper surface of the second heat transfer insulation layer, and around the gas detection electrode by photolithography and multiple low pressure chemical vapor deposition methods;

[0043] 12) preparing a first lead area, a second lead area and a third lead area on the diaphragm structure by photolithography and dry etching the first thermal insulation layer and the second thermal insulation layer; placing the first lead, the second lead and the third lead prepared by laser pulse deposition in the corresponding lead areas respectively to achieve electrical connection;

[0044] 13) The back side of the substrate is etched by photolithography and dry etching, leaving only the frame corresponding to the support area to form the substrate, thereby forming a diaphragm structure and completing the sensor preparation.

[0045] It can be seen from the above technical solutions that the technical solutions of the present invention have the following beneficial effects:

[0046] 1. The present invention utilizes the heat flow between the micro-hotplate and the gas-sensitive film in the gas sensor and rationally utilizes the Nernstow effect to achieve accurate measurement of the temperature of the MEMS micro-hotplate gas sensor, ensure that the reaction temperature is accurately controlled, ensure that the reaction between the gas-sensitive film and the gas to be measured is at the most suitable temperature, and effectively improve the accuracy of the gas sensor; at the same time, the present invention can more accurately measure and control the required temperature of the MEMS micro-hotplate gas sensor gas-sensitive film, thereby effectively improving the energy utilization rate.

[0047] 2. In the present invention, if the reaction temperature of the gas-sensitive film changes, a heat flow will be generated in the heat transfer layer composed of the first heat transfer insulation layer, the heat detection electrode and the second heat transfer insulation layer. The heat detection electrode converts the temperature change into an output voltage change under the action of the Nernst effect, thereby monitoring the reaction temperature change of the gas-sensitive film in real time and realizing precise control of the gas-sensitive film and the gas to be measured to always be at the most suitable reaction temperature.

[0048] 3. The present invention adopts MEMS technology to integrate the temperature measurement structure composed of a heating electrode, a permanent magnetic thin film layer and a heat transfer layer based on the Nernst effect with a micro-hotplate gas sensor on a monolithic chip, thereby realizing collaborative design in terms of process. The volume of the MEMS micro-hotplate gas sensor in the product is effectively reduced, making it suitable for smaller spaces and broadening the application scenarios. Overall, the MEMS micro-hotplate gas sensor of the present invention has the advantages of high precision, good consistency, easy batch manufacturing and low cost.

[0049] It should be appreciated that all combinations of the foregoing concepts, as well as additional concepts described in greater detail below, may be considered to be part of the inventive subject matter of the present disclosure, provided such concepts are not mutually inconsistent.

[0050] The foregoing and other aspects, embodiments and features of the present invention can be more fully understood from the following description in conjunction with the accompanying drawings. Other additional aspects of the present invention, such as the features and / or beneficial effects of the exemplary embodiments, will be apparent from the following description or learned from the practice of the specific embodiments according to the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] The accompanying drawings are not drawn to scale according to actual reference objects. In the accompanying drawings, each identical or nearly identical component shown in various figures may be represented by the same reference numeral. For the sake of clarity, not every component is labeled in each figure. Now, embodiments of various aspects of the present invention will be described by way of example and with reference to the accompanying drawings, in which:

[0052] Figure 1 Shown is a top view schematic diagram of the MEMS micro-hot plate gas sensor disclosed in the present invention;

[0053] Figure 2 The figure shows the MEMS micro-hot plate type gas sensor disclosed by the present invention. Figure 1 A-A' cross-sectional schematic diagram;

[0054] Figure 3 The figure shows a side structural schematic diagram corresponding to the structure of step 1) of the method for preparing a MEMS micro-hot plate gas sensor disclosed in the present invention;

[0055] Figure 4The figure shows a planar structure schematic diagram corresponding to the structure of step 1) of the method for preparing a MEMS micro-hot plate gas sensor disclosed in the present invention;

[0056] Figure 5 The figure shows a side structural schematic diagram corresponding to the first passivation layer structure obtained in step 2) of the method for preparing the MEMS micro-hotplate gas sensor disclosed in the present invention;

[0057] Figure 6 The figure shows a schematic diagram of the planar structure corresponding to the first passivation layer structure obtained in step 2) of the method for preparing the MEMS micro-hotplate gas sensor disclosed in the present invention;

[0058] Figure 7 The figure shows a side structural diagram corresponding to the second passivation layer structure obtained in step 2) of the method for preparing the MEMS micro-hotplate gas sensor disclosed in the present invention;

[0059] Figure 8 The figure shows a side structural diagram corresponding to the second passivation layer structure obtained in step 2) of the method for preparing the MEMS micro-hotplate gas sensor disclosed in the present invention;

[0060] Fig. 9 The figure shows a schematic diagram of the planar structure corresponding to the first metal layer as the first adhesion layer structure in step 3) of the method for preparing the MEMS micro-hotplate gas sensor disclosed in the present invention;

[0061] Fig.10 The figure shows the side structure schematic diagram corresponding to step 3) of the method for preparing the MEMS micro-hotplate gas sensor disclosed in the present invention to prepare the second metal layer as the heating electrode structure;

[0062] Fig.11 It is a schematic diagram of the side structure corresponding to the first thermal insulation layer structure obtained in step 4) of the method for preparing the MEMS micro-hot plate gas sensor disclosed in the present invention;

[0063] Fig.12 The figure shows a side structural diagram corresponding to the permanent magnetic thin film layer structure obtained in step 5) of the method for preparing the MEMS micro-hot plate gas sensor disclosed in the present invention;

[0064] Fig.13 The figure shows a schematic diagram of the planar structure corresponding to the permanent magnetic thin film layer structure obtained in step 5) of the method for preparing the MEMS micro-hotplate gas sensor disclosed in the present invention;

[0065] Fig.14 It is a schematic diagram of the side structure corresponding to the first heat transfer insulation layer structure obtained in step 6) of the method for preparing the MEMS micro-hotplate gas sensor disclosed in the present invention;

[0066] Fig.15It is a schematic diagram of the planar structure corresponding to the first heat transfer insulation layer structure obtained in step 6) of the method for preparing the MEMS micro-hotplate gas sensor disclosed in the present invention;

[0067] Fig.16 The figure shows the side structure schematic diagram corresponding to the step 7) of the method for preparing the MEMS micro-hotplate gas sensor disclosed in the present invention to prepare the third metal layer as the thermal detection electrode structure;

[0068] Fig.17 The figure shows the side structure schematic diagram corresponding to the step 7) of the method for preparing the MEMS micro-hotplate gas sensor disclosed in the present invention to prepare the third metal layer as the thermal detection electrode structure;

[0069] Fig.18 It is a schematic diagram of the side structure corresponding to the second heat transfer insulation layer structure obtained in step 8) of the method for preparing the MEMS micro-hotplate gas sensor disclosed in the present invention;

[0070] Fig.19 It is a schematic diagram of the planar structure corresponding to the second heat transfer insulation layer structure obtained in step 8) of the method for preparing the MEMS micro-hotplate gas sensor disclosed in the present invention;

[0071] Fig. 20 It is a schematic diagram of the side structure corresponding to the structure of the second adhesion layer obtained by preparing the fourth metal layer as step 9) of the method for preparing the MEMS micro-hotplate gas sensor disclosed in the present invention;

[0072] Fig.21 The figure shows the side structure schematic diagram corresponding to the step 9) of the method for preparing the MEMS micro-hotplate gas sensor disclosed in the present invention to prepare the fifth metal layer as the gas detection electrode structure;

[0073] Fig. 22 The figure shows the planar structure schematic diagram corresponding to the fifth metal layer as the gas detection electrode structure in step 9) of the method for preparing the MEMS micro-hotplate gas sensor disclosed in the present invention;

[0074] Fig.23 The figure shows a side structural schematic diagram corresponding to the gas-sensitive film structure obtained in step 10) of the method for preparing the MEMS micro-hotplate gas sensor disclosed in the present invention;

[0075] Fig.24 The figure shows a schematic diagram of the plane structure corresponding to the gas-sensitive film structure obtained in step 10) of the method for preparing the MEMS micro-hotplate gas sensor disclosed in the present invention;

[0076] Fig.25 The figure shows the step 11 of the method for preparing the MEMS micro-hot plate type gas sensor disclosed in the present invention, wherein the second heat insulation layer structure is prepared. Figure 1The corresponding A-A' side structure diagram;

[0077] Fig.26 It is a schematic diagram of the planar structure corresponding to the second thermal insulation layer structure obtained in step 11) of the method for preparing the MEMS micro-hot plate gas sensor disclosed in the present invention;

[0078] Fig. 27 The figure shows a side structural schematic diagram corresponding to the structure obtained in step 12) of the method for preparing a MEMS micro-hot plate gas sensor disclosed in the present invention;

[0079] Fig.28 The figure shows a planar structure schematic diagram corresponding to the structure obtained in step 12) of the method for preparing a MEMS micro-hot plate gas sensor disclosed in the present invention;

[0080] In the figure, the specific meaning of each mark is as follows:

[0081] 1-substrate; 2-support area; 3-sensing area; 4-first passivation layer; 5-second passivation layer; 6-first adhesion area; 7-heating electrode; 8-first thermal insulation layer; 9-permanent magnetic film layer; 10-first heat transfer insulation layer; 11-heat detection electrode; 12-second heat transfer insulation layer; 13-second adhesion area; 14-gas detection electrode; 15-gas sensitive film; 16-second thermal insulation layer; 17-first lead; 18-second lead; 19-third lead; 20-diaphragm structure. DETAILED DESCRIPTION

[0082] In order to make the purpose, technical solution and advantages of the embodiment of the present invention clearer, the technical solution of the embodiment of the present invention will be clearly and completely described below in conjunction with the drawings of the embodiment of the present invention. Obviously, the described embodiment is a part of the embodiment of the present invention, not all of the embodiments. Based on the described embodiment of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. Unless otherwise defined, the technical terms or scientific terms used herein should be the common meaning understood by people with general skills in the field to which the present invention belongs.

[0083] The words "first", "second" and similar words used in the patent application specification and claims of the present invention do not indicate any order, quantity or importance, but are only used to distinguish different components. Similarly, unless the context clearly indicates otherwise, the singular forms of "a", "an" or "the" and other similar words do not indicate a quantitative limitation, but indicate the existence of at least one. Words such as "include" or "comprise" mean that the elements or objects appearing before "include" or "comprise" cover the features, wholes, steps, operations, elements and / or components listed after "include" or "comprise", and do not exclude the existence or addition of one or more other features, wholes, steps, operations, elements, components and / or their collections. "Up", "down", "left", "right" and the like are only used to indicate relative positional relationships. When the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0084] The MEMS micro-hotplate gas sensor adopts the traditional temperature measurement method, such as using a probe to contact the area to be measured or using the principle of thermocouple and thermal resistor to measure the temperature. Due to the small size of the sensor, the temperature measurement accuracy is low; at the same time, the traditional contact measurement will cause the temperature distribution of the sensor to change, causing the heat transfer efficiency of the micro-hotplate to decrease; in addition, since the gas-sensitive film needs to be in contact with the gas to be measured, and the existing temperature measurement structure needs to touch the gas-sensitive film for measurement, if the contact is long-term, it will occupy the area of ​​the reaction interface between the gas-sensitive film and the gas to be measured, resulting in a decrease in reaction efficiency, and short-term contact will not be able to dynamically monitor the reaction temperature of the gas sensor in real time. Therefore, the present invention proposes a MEMS micro-hotplate gas sensor with a thermal magnetic temperature measurement structure and a preparation method thereof, which uses a thermal magnetic temperature measurement structure to replace the traditional temperature measurement method, without touching the gas-sensitive film, while solving the problems existing in the traditional temperature measurement method, it can further improve the accuracy and sensitivity of the sensor.

[0085] The following is a further detailed introduction to the MEMS micro-hot plate gas sensor with a thermal magnetic temperature measurement structure and a preparation method thereof disclosed in the present invention in conjunction with the specific embodiments shown in the accompanying drawings.

[0086] Combination Figure 1 and Figure 2 As shown, the MEMS micro-hotplate gas sensor with a thermal magnetic temperature measurement structure disclosed in the embodiment includes a substrate 1 and a diaphragm structure 20 arranged above the substrate 1.

[0087] As shown in the figure, the diaphragm structure 20 includes a passivation layer, a heating electrode 7, a permanent magnetic film layer 9, a first heat transfer insulation layer 10, a heat detection electrode 11, a second heat transfer insulation layer 12, a gas detection electrode 14 and a gas sensitive film 15 stacked from bottom to top; wherein the heating electrode 7 is used as a heat source, and the heat flow generated by it is transmitted to the sensing area 3 through the passivation layer, and the other heat flow is transmitted to the gas sensitive film 15 through the first heat transfer insulation layer 10, the heat detection electrode 11, and the second heat transfer insulation layer 12; the gas sensitive film 15 receives the heat flow and is heated to the working temperature range to react chemically with the gas to be measured, and then changes its own resistance, and the gas detection electrode 14 detects the resistance and calculates and converts it to obtain the concentration of the gas to be measured; the permanent magnetic film layer 9 generates a magnetic field when the MEMS micro-hot plate gas sensor is in a working state, and the heat detection electrode 11 converts the reaction temperature change of the gas sensitive film 15 into an output voltage change based on the Nernst effect, thereby realizing real-time monitoring of the reaction temperature of the gas sensitive film 15.

[0088] Optionally, the reasons causing the reaction temperature change of the gas-sensitive film 15 during the application of the MEMS micro-hotplate gas sensor include but are not limited to changes in the external environment temperature of the sensor, changes in the heating power of the heating electrode, and temperature changes caused by different chemical reaction processes between the gas-sensitive film and the gas to be measured.

[0089] Combination Figures 3 to 28 As shown, the preparation method of the above-mentioned MEMS micro-hot plate gas sensor with a thermal magnetic temperature measurement structure is introduced in detail as follows step by step.

[0090] 1) A silicon wafer is selected as a substrate, the upper surface of the substrate is horizontal, the middle of which is divided into a sensing area 3 of a cross structure, the periphery of the sensing area 3 is divided into a supporting area 2, and the supporting area 2 is set as a frame for supporting the cross structure, which is set as a rectangular frame in the figure;

[0091] The substrate material is usually single crystal silicon with a thickness of 200 to 1000 μm. Figure 3 The substrate 1 is a 200 μm thick N-type (100) silicon wafer obtained by etching. The sensing area 3 is a cross structure arranged in the middle of the upper surface of the substrate 1, the purpose of which is to divide and position each layer of the subsequent diaphragm structure 20. The purpose of arranging each layer in the sensor according to the cross structure is to reduce unnecessary heat conduction, reduce power consumption, and improve response time. In the initial stage, the support area 2 and the sensing area 3 are used to provide support for the manufacture of the diaphragm structure 20, and the subsequent support area 2 provides space for the lead wires of each electrode of the sensor.

[0092] 2) sequentially preparing a first passivation layer 4 and a second passivation layer 5 on the upper surfaces of the support area 2 and the sensing area 3 by photolithography and low pressure chemical vapor deposition;

[0093] The first passivation layer 4 is located on the upper surface of the support area 2 and the sensing area 3, and its planar structure corresponds to the frame of the support area 2 and the cross structure of the sensing area 3, such as Figure 5 and Figure 6 As shown; the material of the first passivation layer is silicon nitride, with a thickness of 100 to 500 nm, and a thickness of 200 nm is selected in the embodiment;

[0094] The second passivation layer 5 is located on the upper surface of the first passivation layer 4, and its planar structure corresponds to the planar structure of the first passivation layer 4. Figure 7 As shown; the material of the second passivation layer is silicon dioxide, with a thickness of 100 to 500 nm, and a thickness of 200 nm is selected in the embodiment.

[0095] 3) preparing a first metal layer and a second metal layer on the upper surface of the second passivation layer 5 by photolithography and magnetron sputtering, as the first adhesion area 6 and the heating electrode 7, that is, the heating electrode 7 is fixed on the upper surface of the second passivation layer 5 through the first adhesion area 6;

[0096] In the embodiment, the first metal layer is a metal titanium layer with a thickness of 100 nm, which is formed on the upper surface of the second passivation layer 5 as the first adhesion area 6; the second metal layer is a first metal platinum layer with a thickness of 200 nm, which is formed on the upper surface of the first adhesion area 6 to constitute a heating electrode 7; the plane structure of the heating electrode 7 corresponds to the two lateral arms and the central position of the cross structure of the sensing area 3; the shape of the partial plane structure of the heating electrode corresponding to the center of the cross structure is set to a serpentine structure, and the crests and troughs of the serpentine structure extend in the direction of the two longitudinal arms of the cross structure, such as Fig.10 In the embodiment, the planar structure of the first adhesion area 6 is the same as the planar structure of the heating electrode 7, as shown in FIG. Figure 8 and Fig. 9 shown.

[0097] The heating electrode 7 is used as a heat source and serves as the main structure of the micro-hotplate of the MEMS micro-hotplate gas sensor, providing the optimal working temperature required for the gas-sensitive film 15 to react with the gas to be measured. In addition, the central plane shape of the heating electrode 7 is designed as a densely distributed serpentine structure, the purpose of which is to increase the heating resistance and the heating area, improve the heating efficiency, and achieve uniform heat transfer.

[0098] In order to maintain the heat insulation effect on the heating electrode 7, reduce the heat conduction between the planes, and reduce unnecessary heat loss; the diaphragm structure 20 also includes a first heat insulation layer 8, which can also serve as a supporting structure to prevent the first adhesion area 6 and the serpentine structure of the heating electrode 7 from being deformed due to heat. Therefore, after the preparation of the heating electrode 7 is completed in step 3), the first heat insulation layer 8 is prepared.

[0099] 4) preparing a first heat-insulating layer 8 on the upper surface of the second passivation layer 5 and around the heating electrode 7 by photolithography and low-pressure chemical vapor deposition;

[0100] Based on the heating electrode 7 being fixed on the surface of the second passivation layer 5 by the first adhesion area 6, the first heat-insulating layer 8 is simultaneously deposited around the first adhesion area 6; in the embodiment, the first heat-insulating layer 8 is a silicon dioxide layer with a thickness of 300 nm, the upper surface of which is flush with the upper surface of the heating electrode 7, and the portion thereof located around the first adhesion area 6 and the heating electrode 7 fully fills the gap of the serpentine structure, such as Fig.11 shown.

[0101] 5) preparing an alloy layer as a permanent magnetic film layer 9 on the upper surface of the heating electrode 7 and the first thermal insulation layer 8 by photolithography and magnetron sputtering;

[0102] The permanent magnetic film layer 9 is arranged on the upper surface of the heating electrode 7 and the first heat-insulating layer 8, and its plane structure corresponds to the upper side of the four extension arms of the cross structure of the sensing area 3; the permanent magnetic film layer 9 is the same as providing the magnetic field required for the Nernstow effect, and can be composed of FePt, CoPt, CoNiMnP or Sr ferrite, with a thickness of 1 to 5 um; in the accompanying drawings, the permanent magnetic film layer 9 is composed of a cobalt-platinum alloy with a thickness of 2 um, and the specific position is as follows Fig.12 and Fig.13 shown.

[0103] 6) preparing a first heat transfer insulation layer 10 on the upper surfaces of the heating electrode 7, the first heat insulation layer 8, and the permanent magnetic film layer 9 by photolithography and plasma enhanced chemical vapor deposition;

[0104] The upper surface of the first heat transfer insulating layer 10 is horizontal, and its bottom is arranged on the upper surface of the heating electrode 7, the first heat insulation insulating layer 8 and the permanent magnetic film layer 9; in the example, the plane structure of the first heat transfer insulating layer corresponds to the cross structure of the sensing area 3, the thickness is 2.1-2.2um, and the material is aluminum nitride, such as Fig.14 and Fig.15 As shown; the first heat transfer insulating layer 10 is used in the sensor on the one hand to transfer the heat generated by the heating electrode 7, generating a horizontal heat flow so as to enable more uniform heating, and on the other hand to form electrical isolation.

[0105] 7) preparing a third metal layer on the upper surface of the first heat transfer insulating layer 10 by photolithography and magnetron sputtering, as a heat detection electrode 11;

[0106] In the embodiment, the third metal layer is a metal copper layer with a thickness of 1 um, and the metal copper layer on the upper surface of the first heat transfer insulating layer 10 is set as the heat detection electrode 11. The plane structure of the heat detection electrode 11 corresponds to the cross structure of the sensing area 3, and the ends of the four extension arms on the plane structure of the heat detection electrode are respectively preset with electrode lead-out spaces for the heating electrode, such as Fig.16 and Fig.17 As shown; the first heat transfer insulating layer 10 is also used to form electrical isolation between the heating electrode 7 and the thermal detection electrode 11.

[0107] When the sensor is working, the permanent magnetic film layer 9 generates a magnetic field that passes perpendicularly through the thermal detection electrode 11. There is a heat flow on the thermal detection electrode 11 that is transmitted along its center to the four arms of the cross structure. Based on the Nernstow effect, an electromotive force is generated on both sides of the thermal detection electrode 11 that are perpendicular to the heat flow direction. In addition, because heat flows in four directions are formed on the cross structure of the thermal detection electrode, four induced electromotive forces can be generated in theory; through reasonable circuit design, the output value of the detection voltage can be increased; and more accurate temperature measurement can be achieved through mutual correction of the induced potentials of each branch.

[0108] Therefore, when the heating power of the heating electrode 7 changes, or the external ambient temperature changes, a new heat flow will be generated in the thermal detection electrode 11, thereby realizing real-time detection of the reaction temperature.

[0109] In addition, when the sensor is used, a suitable algorithm can be selected to solve the corresponding differential equation according to the output voltage of the thermal detection electrode 11 to obtain the temperature distribution of the entire heat transfer layer; thereby, the heating power of the heating electrode 7 can be adjusted according to the measured temperature, thereby improving the accuracy of the sensor and reducing the power consumption of the sensor.

[0110] 8) preparing a second heat transfer insulating layer 12 on the upper surface of the first heat transfer insulating layer 10 and the heat detection electrode 11 by photolithography and plasma enhanced chemical vapor deposition;

[0111] The upper surface of the second heat transfer insulating layer 12 is horizontal, and its bottom is arranged on the upper surface of the first heat transfer insulating layer 10 and the heat detection electrode 11; the thickness of the second heat transfer insulating layer 12 is 100-300nm, and its plane structure corresponds to the cross structure of the sensing area 3; in the example, the second heat transfer insulating layer 12 with a thickness of 100nm is prepared by aluminum nitride deposition, as shown in FIG. Fig.18 and Fig.19 shown.

[0112] 9) preparing a fourth metal layer and a fifth metal layer on the upper surface of the second heat transfer insulating layer by photolithography and magnetron sputtering, as the second adhesion area and the gas detection electrode, that is, the gas detection electrode is fixed on the upper surface of the second heat transfer insulating layer through the second adhesion area;

[0113] In the embodiment, the fourth metal layer is a metal titanium layer with a thickness of 100 nm, which is formed on the upper surface of the second heat transfer insulating layer 12 as the second adhesion area 13. Fig. 20 As shown; the fifth metal layer is a second metal platinum layer with a thickness of 200nm formed on the upper surface of the second adhesion area 13, and the second metal platinum layer constitutes the gas detection electrode 14; that is, the gas detection electrode 14 is fixed on the upper surface of the second heat transfer insulation layer 12 using the second adhesion area 13; the plane structure of the gas detection electrode 14 corresponds to the longitudinal two arms and the central position of the cross structure of the sensing area 3, as shown Fig.21 and Fig. 22 As shown, the shape of the partial planar structure of the gas detection electrode 14 corresponding to the center of the cross structure is set to a comb-tooth structure, and the comb-tooth structure is staggered in the two lateral arms of the cross structure; the second heat transfer insulating layer 12 is used to form electrical isolation between the heat detection electrode 11 and the gas detection electrode 14, and the gas detection electrode 14 is used to detect the electrical quantity of different regions of the gas sensitive film 15, that is, the resistance value, to a certain extent to eliminate the situation of uneven regional reaction and improve the accuracy of the gas sensor. In the embodiment, the planar structure of the second adhesion area 13 is the same as the planar structure of the gas detection electrode 14.

[0114] 10) A gas-sensitive film 15 is prepared on the upper surface of the gas detection electrode 14 by photolithography and spin coating, such as Fig.23 and Fig.24 As shown, the planar structure of the gas sensitive film 15 corresponds to the planar structure of the gas detection electrode 14; the specific material and thickness of the gas sensitive film 15 are determined by the gas to be detected. If the gas to be detected is ethanol gas, Pt-doped SnO2 with a thickness of 5um can be selected.

[0115] In order to form electrical isolation between the heating electrode 7, the heat detection electrode 11, and the gas detection electrode 14, and at the same time form heat isolation between the first heat transfer insulation layer 10 and the outside world, the diaphragm structure 20 is also provided with a second heat insulation layer 16; therefore, after the preparation of the gas-sensitive film 15 is completed in step 10), the second heat insulation layer 16 is prepared.

[0116] 11) A second thermal insulation layer 16 is prepared on the first thermal insulation layer 8, the upper surface of the second heat transfer insulation layer 12, and around the gas detection electrode 14 by photolithography and multiple low-pressure chemical vapor deposition methods; since the gas detection electrode 14 is fixed on the upper surface of the second heat transfer insulation layer 12 through the second adhesion area 13, when the second thermal insulation layer 16 is prepared, it is also simultaneously deposited around the second adhesion area 13, and its portion located around the second adhesion area 13 and the gas detection electrode 14 fully fills the gaps in the comb-tooth structure.

[0117] like Fig.25 and Fig.26 As shown, the upper surface of the second thermal insulation layer 16 is flush with the upper surface of the gas sensitive film 15, and the planar structure of the second thermal insulation layer 16 corresponds to the cross structure of the supporting area 2 and the sensing area 3; in the example, the second thermal insulation layer 16 has a thickness of 100 nm and is made of silicon dioxide.

[0118] In order to achieve electrical connection of the entire diaphragm structure 20 , the diaphragm structure 20 further includes a first lead 17 , a second lead 18 and a third lead 19 . Therefore, after the second thermal insulation layer 16 is prepared, the leads are introduced into the structure.

[0119] 12) The first thermal insulation layer 8 and the second thermal insulation layer 16 are etched by photolithography and dry etching to prepare a first lead area, a second lead area and a third lead area on the diaphragm structure 20, and each lead exposes a corresponding electrode; the first lead 17, the second lead 18 and the third lead 19 prepared by laser pulse deposition are respectively placed in the corresponding lead areas to achieve electrical connection; in the embodiment, the size of the first lead 17, the second lead 18 and the third lead 19 is a metal copper strip adapted to the size of the corresponding lead area, specifically as follows Fig. 27 and Fig.28 As shown; the first lead 17 is located in the first thermal insulation layer 8 and the second thermal insulation layer 16, and is electrically connected to the heating electrode 7, and its thickness is the distance from the bottom surface of the heating electrode 7 to the upper surface of the diaphragm structure 20; the second lead 18 is located in the second thermal insulation layer 16, and is electrically connected to the thermal detection electrode 11, and its thickness is the distance from the bottom surface of the thermal detection electrode 11 to the upper surface of the diaphragm structure 20; the third lead 19 is located in the second thermal insulation layer 16, and is electrically connected to the gas detection electrode 14, and its thickness is the distance from the bottom surface of the gas detection electrode 14 to the upper surface of the diaphragm structure 20.

[0120] 13) The back of the substrate 1 is etched by photolithography and dry etching, and only the rectangular frame corresponding to the support area 2 is retained to form the substrate 1, forming a diaphragm structure 20, and completing the sensor preparation; the plane structure of the final product is as follows Figure 1 As shown, Figure 2 For along Figure 1 The cross section along the AA′ direction shows that the membrane structure 20 disposed on the upper surface of the substrate 1 takes the cross structure in the middle of the first passivation layer 4 as the base.

[0121] The working principle of the MEMS micro-hotplate gas sensor with a thermal magnetic temperature measurement structure disclosed in the above embodiment of the present invention is as follows:

[0122] The first heat transfer insulating layer 10, the heat detection electrode 11, and the second heat transfer insulating layer 12 of the diaphragm structure 20 constitute the heat transfer layer of the MEMS micro-hotplate gas sensor, and the heat transfer layer is a cross structure as a whole; the heating electrode 7 is used as a heat source, and the heat flow generated by it starts from the center of the cross structure, flows along the cross arm on the one hand, and flows upward to the gas sensitive film 15 on the other hand, so that the gas sensitive film is heated. The heating electrode 7, the first heat transfer insulating layer 10, the second heat transfer insulating layer 12, the gas detection electrode 14 and the gas sensitive film 15 in the diaphragm structure 20 together constitute the gas detection structure of the MEMS micro-hotplate gas sensor; when the heating electrode (7) heats the gas sensitive film 15 to a suitable working temperature range, the gas sensitive film 15 reacts chemically with the gas to be detected, thereby changing the resistance of the gas sensitive film 15, and the resistance value is read through the gas detection electrode (14), and the corresponding physical quantity of the gas to be detected, that is, the concentration, is obtained through the corresponding algorithm conversion. The heating electrode (7), the permanent magnetic film layer (9) and the heat transfer layer in the diaphragm structure 20 together constitute the temperature detection structure of the MEMS micro-thermal plate type gas sensor; when the permanent magnetic film layer (9) generates a magnetic field perpendicular to the heat transfer layer, based on the Nernstow effect, an electromotive force is generated on both sides of the heat detection electrode (11), and the temperature distribution of the entire heat transfer layer can be obtained through a corresponding algorithm, thereby achieving accurate temperature measurement; as long as the reaction temperature of the gas-sensitive film 15 changes (such as gas contact in a low-temperature environment), a heat flow will be formed in the heat transfer layer, and then the reaction temperature of the gas-sensitive film 15 can be measured in real time; and by correcting the heating power, the accuracy of the gas sensor can be further improved.

[0123] Although the present invention has been disclosed as above with preferred embodiments, it is not intended to limit the present invention. A person with ordinary knowledge in the technical field to which the present invention belongs may make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention shall be determined by the definition of the claims.

Claims

1. A MEMS micro-hotplate gas sensor with a thermal magnetic temperature measurement structure, characterized in that: It includes a substrate and a diaphragm structure arranged above the substrate; the middle part of the substrate is divided into a sensing area of ​​a cross structure; The diaphragm structure includes a passivation layer, a heating electrode, a permanent magnetic film layer, a first heat transfer insulation layer, a heat detection electrode, a second heat transfer insulation layer, a gas detection electrode and a gas sensitive film stacked from bottom to top; the heating electrode is used as a heat source, and the heat flow generated by it is transmitted to the sensing area through the passivation layer in one way, and the other heat flow is transmitted to the gas sensitive film through the first heat transfer insulation layer, the heat detection electrode and the second heat transfer insulation layer; the gas sensitive film receives the heat flow and heats up to the working temperature range, reacts chemically with the gas to be measured, and changes its own resistance, which is detected by the gas detection electrode and converted into the concentration of the gas to be measured; the permanent magnetic film layer generates a magnetic field when the MEMS micro-hot plate gas sensor is in a working state, and the heat detection electrode converts the reaction temperature change of the gas sensitive film into an output voltage change based on the Nernst effect, thereby realizing real-time monitoring of the reaction temperature of the gas sensitive film.

2. The MEMS micro-hotplate gas sensor with a thermal magnetic temperature measurement structure according to claim 1, characterized in that: The passivation layer is arranged on the substrate, the middle part of the passivation layer is horizontally arranged as a cross structure, and the outer periphery of the passivation layer is arranged as a frame for supporting the cross structure; The heating electrode is fixed on the upper surface of the passivation layer, and its plane structure corresponds to the two horizontal arms and the central position of the cross structure; the shape of the partial plane structure of the heating electrode corresponding to the center of the cross structure is set to a serpentine structure, and the crests and troughs of the serpentine structure extend toward the two longitudinal arms of the cross structure.

3. The MEMS micro-hotplate gas sensor with a thermal magnetic temperature measurement structure according to claim 2, characterized in that: The diaphragm structure also includes a first thermal insulation layer; The first heat-insulating layer is located on the upper surface of the passivation layer and around the heating electrode, its upper surface is flush with the upper surface of the heating electrode, and its portion located around the heating electrode fully fills the gaps in the serpentine structure.

4. The MEMS micro-hotplate gas sensor with a thermal magnetic temperature measurement structure according to claim 3, characterized in that: The permanent magnetic film layer is arranged on the upper surface of the heating electrode and the first thermal insulation layer, and its plane structure corresponds to the top of the four extension arms of the cross structure; the permanent magnetic film layer is composed of FePt, CoPt, CoNiMnP or Sr ferrite, and has a thickness of 1 to 5um.

5. The MEMS micro-hotplate gas sensor with a thermal magnetic temperature measurement structure according to claim 4, characterized in that: The upper surface of the first heat transfer insulation layer is horizontal, and its bottom is arranged on the upper surfaces of the heating electrode, the first heat insulation layer and the permanent magnetic film layer; the thickness of the first heat transfer insulation layer is 2.1 to 2.2 um, and its plane structure corresponds to the cross structure; the first heat transfer insulation layer is used to generate horizontal heat flow while transferring heat.

6. The MEMS micro-hotplate gas sensor with a thermal magnetic temperature measurement structure according to claim 5, characterized in that: The heat detection electrode is disposed on the upper surface of the first heat transfer insulation layer; The planar structure of the heat detection electrode corresponds to the cross structure; The ends of the four extension arms on the planar structure of the thermal detection electrode are respectively provided with electrode lead-out spaces for the heating electrodes; The permanent magnetic film layer is used to generate a magnetic field perpendicular to the heat detection electrode. There is a heat flow on the heat detection electrode that is transmitted along the center of the heat detection electrode to the four arms of the cross structure. Based on the Nernstow effect, an electromotive force is generated on both sides of the heat detection electrode that are perpendicular to the heat flow direction. The first heat transfer insulating layer is used to electrically isolate the heating electrode from the heat detection electrode.

7. The MEMS micro-hotplate gas sensor with a thermal magnetic temperature measurement structure according to claim 6, characterized in that: The upper surface of the second heat transfer insulation layer is horizontal, and its bottom is arranged on the upper surface of the first heat transfer insulation layer and the heat detection electrode; the thickness of the second heat transfer insulation layer is 100-300nm, and its plane structure corresponds to the cross structure.

8. The MEMS micro-hotplate gas sensor with a thermal magnetic temperature measurement structure according to claim 7, characterized in that: The gas detection electrode is fixedly arranged on the upper surface of the second heat transfer insulating layer, and its plane structure corresponds to the two longitudinal arms and the central position of the cross structure; the shape of the partial plane structure of the gas detection electrode corresponding to the central position of the cross structure is set as a comb tooth structure, and the comb tooth structure is staggered along the two transverse arms of the cross structure, and is used to detect the electrical quantities of different areas of the gas sensitive film; The gas-sensitive film is located above the gas detection electrode, and its plane structure corresponds to the gas detection electrode; The second heat transfer insulating layer is used to electrically isolate the heat detection electrode from the gas detection electrode.

9. The MEMS micro-hotplate gas sensor with a thermal magnetic temperature measurement structure according to claim 8, characterized in that: The diaphragm structure also includes a second thermal insulation layer; The second thermal insulation layer is located on the first thermal insulation layer and the second heat transfer insulation layer, and its upper surface is flush with the upper surface of the gas sensitive film, and the planar structure of the second thermal insulation layer corresponds to the frame and the cross structure; the second thermal insulation layer is used to form electrical isolation between the heating electrode, the heat detection electrode, and the gas detection electrode, and is used to simultaneously form heat isolation between the second heat transfer insulation layer and the outside world.

10. The MEMS micro-hotplate gas sensor with a thermal magnetic temperature measurement structure according to claim 9, characterized in that: The diaphragm structure further includes a first lead, a second lead and a third lead; The first lead is located in the first heat-insulating layer and the second heat-insulating layer, and is electrically connected to the heating electrode. The thickness of the first lead is the distance from the bottom surface of the heating electrode to the upper surface of the diaphragm structure. The second lead is located in the second heat-insulating layer and is electrically connected to the heat detection electrode. The thickness of the second lead is the distance from the bottom surface of the heat detection electrode to the upper surface of the diaphragm structure. The third lead is located in the second heat-insulating layer and is electrically connected to the gas detection electrode. The thickness of the third lead is the distance from the bottom surface of the gas detection electrode to the upper surface of the diaphragm structure.

11. The MEMS micro-hotplate gas sensor with a thermal magnetic temperature measurement structure according to claim 2, characterized in that: The passivation layer includes a first passivation layer and a second passivation layer; The first passivation layer is located on the upper surface of the substrate, and its planar structure includes the cross structure located in the middle and a frame supporting the cross structure; The material of the first passivation layer is silicon nitride, and the thickness is 100-500nm; The second passivation layer is located on the upper surface of the first passivation layer, and its planar structure corresponds to the planar structure of the first passivation layer; the material of the second passivation layer is silicon dioxide, and the thickness is 100-500nm.

12. The method for preparing a MEMS micro-hotplate gas sensor with a thermal magnetic temperature measurement structure according to any one of claims 1 to 11, characterized in that: The steps include: 1) A silicon wafer is selected as a substrate, the upper surface of the substrate is horizontal, the middle part of the substrate is divided into a sensing area of ​​a cross structure, the periphery of the sensing area is divided into a supporting area, and the supporting area is set as a frame for supporting the cross structure; 2) sequentially preparing a first passivation layer and a second passivation layer on the upper surfaces of the support area and the sensing area by photolithography and low pressure chemical vapor deposition; 3) preparing a first metal layer and a second metal layer on the upper surface of the second passivation layer by photolithography and magnetron sputtering, as a first adhesion area and a heating electrode, that is, the heating electrode is fixedly arranged on the upper surface of the second passivation layer through the first adhesion area; 4) preparing a first heat-insulating layer on the upper surface of the second passivation layer and around the heating electrode by photolithography and low-pressure chemical vapor deposition; 5) preparing an alloy layer as a permanent magnetic film layer on the upper surface of the heating electrode and the first thermal insulation layer by photolithography and magnetron sputtering; 6) preparing a first heat transfer insulation layer on the upper surface of the heating electrode, the first heat insulation layer, and the permanent magnetic film layer by photolithography and plasma enhanced chemical vapor deposition; 7) preparing a third metal layer on the upper surface of the first heat transfer insulating layer by photolithography and magnetron sputtering to serve as a heat detection electrode; 8) preparing a second heat transfer insulation layer on the upper surface of the first heat transfer insulation layer and the heat detection electrode by photolithography and plasma enhanced chemical vapor deposition; 9) preparing a fourth metal layer and a fifth metal layer on the upper surface of the second heat transfer insulating layer by photolithography and magnetron sputtering, as the second adhesion area and the gas detection electrode, that is, the gas detection electrode is fixed on the upper surface of the second heat transfer insulating layer through the second adhesion area; 10) preparing a gas-sensitive film on the upper surface of the gas detection electrode by photolithography and spin coating; 11) preparing a second thermal insulation layer on the first thermal insulation layer, the upper surface of the second heat transfer insulation layer, and around the gas detection electrode by photolithography and multiple low pressure chemical vapor deposition methods; 12) preparing a first lead area, a second lead area and a third lead area on the diaphragm structure by photolithography and dry etching the first thermal insulation layer and the second thermal insulation layer; placing the first lead, the second lead and the third lead prepared by laser pulse deposition in the corresponding lead areas respectively to achieve electrical connection; 13) The back side of the substrate is etched by photolithography and dry etching, leaving only the frame corresponding to the support area to form the substrate, thereby forming a diaphragm structure and completing the sensor preparation.

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