CN118010808A - MEMS micro-thermal plate type gas sensor with thermo-magnetic temperature measuring structure and preparation method thereof - Google Patents
MEMS micro-thermal plate type gas sensor with thermo-magnetic temperature measuring structure and preparation method thereof Download PDFInfo
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Abstract
The invention provides a MEMS micro-thermal plate type gas sensor with a thermo-magnetic temperature measuring structure and a preparation method thereof, relating to the field of sensors; the sensor includes a substrate and a diaphragm structure disposed over the substrate; the membrane structure comprises a passivation layer, a heating electrode, a permanent magnet film layer, a first heat transfer insulating layer, a heat detection electrode, a second heat transfer insulating layer, a gas detection electrode and a gas-sensitive film which are arranged in a stacked manner from bottom to top; when in operation, the heating electrode is used as a heat source to generate heat which is respectively transferred to the sensing area and the gas-sensitive film; the gas-sensitive film receives heat flow, and changes the resistance after the heat flow is heated to the working temperature range and reacts with the gas to be detected, and the heat flow is converted into the concentration of the gas to be detected after being detected by the gas detection electrode; the permanent magnet film layer generates a magnetic field when working, and the thermal detection electrode converts the reaction temperature change of the gas-sensitive film into output voltage change based on the Nernst effect, so that the reaction temperature of the gas-sensitive film is monitored in real time.
Description
Technical Field
The invention relates to the technical field of sensors, in particular to a MEMS micro-thermal plate type gas sensor with a thermo-magnetic temperature measuring structure and a preparation method thereof.
Background
With the development of society, there is a growing need to measure the concentration of various gases in real time in more and more scenes in social life. The principle of the MEMS micro-hotplate type gas sensor is that the electric characteristics of the gas-sensitive film are changed by utilizing the reaction of the gas and the gas-sensitive film, so that the concentration of the gas to be measured is obtained, wherein the micro-hotplate is used for heating the gas-sensitive film, and the reaction speed and the conversion rate are improved. In addition, MEMS micro-hotplate gas sensors are increasingly favored for their advantages of miniaturization, low cost, high reliability, ease of integration, etc.
For the MEMS micro-hot plate type gas sensor, the reaction degree of the gas-sensitive film and the gas to be detected is increased and then reduced along with the temperature rise, so that the gas-sensitive film of the micro-hot plate type gas sensor needs to be controlled at a proper temperature to achieve the maximum reaction degree in order to achieve higher precision and sensitivity, and therefore the temperature of the gas sensor needs to be detected and controlled. The traditional temperature measurement mode of the micro-hot plate type gas sensor is to use a probe to contact a region to be measured and measure by utilizing the principle of a thermocouple or a thermal resistor, but the MEMS micro-hot plate type gas sensor is inaccurate in temperature measurement due to small size and even smaller than the probe size. Meanwhile, the traditional contact measurement can cause the problems of change of sensor temperature distribution, reduction of heat transfer efficiency of a micro-hotplate and the like. In addition, because the gas-sensitive film needs to be contacted with the gas to be measured, the existing temperature measuring structure needs to touch the gas-sensitive film for measurement, if the gas-sensitive film is contacted for a long time, the area of a reaction interface between the gas-sensitive film and the gas to be measured is occupied, so that the reaction efficiency is reduced, and the reaction temperature of the gas sensor cannot be dynamically monitored in real time when the gas-sensitive film is contacted for a short time.
Disclosure of Invention
The invention aims to provide an MEMS micro-thermal plate type gas sensor with a thermo-magnetic temperature measuring structure and a preparation method thereof, which can realize accurate and real-time measurement of the reaction temperature of gas to be measured and a gas-sensitive film and further improve the accuracy and sensitivity of the MEMS micro-thermal plate type gas sensor.
In order to achieve the above purpose, the present invention proposes the following technical scheme:
in a first aspect, a MEMS micro-hotplate gas sensor with a thermo-magnetic temperature measurement structure is disclosed, comprising a substrate and a diaphragm structure arranged above the substrate;
The membrane structure comprises a passivation layer, a heating electrode, a permanent magnet film layer, a first heat transfer insulating layer, a heat detection electrode, a second heat transfer insulating layer, a gas detection electrode and a gas-sensitive film which are arranged in a stacked manner from bottom to top; the heating electrode is used as a heat source, one path of heat flow generated by the heating electrode is transmitted to the sensing area through the passivation layer, and the other path of heat flow is transmitted to the gas-sensitive film through the first heat transfer insulating layer, the heat detection electrode and the second heat transfer insulating layer; the gas-sensitive film receives heat flow, heats the heat flow to a working temperature range, and changes self resistance after the heat flow and the gas to be detected undergo chemical reaction, and the heat flow is detected by the gas detection electrode and converted into the concentration of the gas to be detected; the permanent magnet film layer generates a magnetic field when the MEMS micro-hotplate type gas sensor is in a working state, and the thermal detection electrode converts the reaction temperature change of the gas-sensitive film into output voltage change based on the Nernst effect, so that the reaction temperature of the gas-sensitive film is monitored in real time.
Further, the passivation layer is arranged on the substrate, the middle part of the passivation layer is horizontally arranged to be of a cross structure, and the peripheral ring of the passivation layer is arranged to be a frame for supporting the cross structure;
The heating electrode is fixedly arranged on the upper surface of the passivation layer, and the plane structure of the heating electrode corresponds to the transverse two arms and the central position of the cross structure; the heating electrode is arranged in a serpentine structure corresponding to the shape of a part of the planar structure in the center of the cross structure, and the wave crests and wave troughs of the serpentine structure extend towards the two longitudinal arm directions of the cross structure.
Further, the membrane structure further comprises a first heat-insulating layer;
the first heat-insulating layer is positioned on the upper surface of the passivation layer and around the heating electrode, the upper surface of the first heat-insulating layer is flush with the upper surface of the heating electrode, and the part of the first heat-insulating layer positioned around the heating electrode is used for fully filling the gap of the serpentine structure.
Further, the permanent magnetic film layer is arranged on the upper surfaces of the heating electrode and the first heat insulation layer, and the plane structure of the permanent magnetic film layer corresponds to the upper parts 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 1-5 um.
Further, the upper surface of the first heat transfer insulating layer is horizontal, and the bottom of the first heat transfer insulating layer is arranged on the upper surfaces of the heating electrode, the first heat insulation insulating layer and the permanent magnetic film layer; the thickness of the first heat transfer insulating layer is 2.1-2.2 um, and the plane structure of the first heat transfer insulating layer corresponds to the cross structure; the first heat transfer insulating layer is used for generating horizontal heat flow while transferring heat.
Further, the heat detection electrode is arranged on the upper surface of the first heat transfer insulating layer; the plane structure of the thermal detection electrode corresponds to the cross structure;
Electrode leading-out spaces for the heating electrodes are respectively preset at the tail ends of the four extension arms on the plane structure of the heat detection electrode;
the permanent magnetic film layer is used for generating a magnetic field vertically passing through the heat detection electrode, and the heat detection electrode is provided with heat flow which is transmitted to the four arms of the cross structure along the center of the heat detection electrode, so that based on the Nernst effect, electromotive force is generated on two sides of the heat detection electrode, which are vertical to the heat flow direction;
The first heat transfer insulating layer is used for forming electric isolation between the heating electrode and the thermal detection electrode.
Further, the upper surface of the second heat transfer insulating layer is horizontal, and the bottom of the second heat transfer insulating layer is arranged on the upper surfaces of the first heat transfer insulating layer and the heat detection electrode; the thickness of the second heat transfer insulating layer is 100-300 nm, and the plane structure of the second heat transfer insulating layer corresponds to the cross structure.
Further, the gas detection electrode is fixedly arranged on the upper surface of the second heat transfer insulating layer, and the plane structure of the gas detection electrode corresponds to the longitudinal two arms and the central position of the cross structure; the shape of the part of the plane structure of the gas detection electrode corresponding to the center of the cross structure is set to be a comb tooth structure, and the comb tooth structure is staggered in opposite directions along the two transverse arm directions of the cross structure and is used for detecting the electric quantity of different areas of the gas-sensitive film;
The gas-sensitive film is positioned above the gas detection electrode, and the plane structure of the gas-sensitive film corresponds to the gas detection electrode;
The second heat transfer insulating layer is used for forming electric isolation between the thermal detection electrode and the gas detection electrode.
Further, the membrane structure further comprises a second heat-insulating layer;
The second heat insulation layer is positioned on the first heat insulation layer and the second heat transfer insulation layer, the upper surface of the second heat insulation layer is flush with the upper surface of the gas-sensitive film, and the plane structure of the second heat insulation layer corresponds to the frame and the cross structure; the second heat-insulating layer is used for forming electric isolation among the heating electrode, the heat detection electrode and the gas detection electrode, and is used for simultaneously forming heat isolation between the second heat-transfer insulating layer and the outside.
Further, the membrane structure further comprises a first lead, a second lead and a third lead;
The first lead is positioned in the first heat insulation layer and the second heat insulation layer, is electrically connected with the heating electrode, and has the thickness of the distance from the bottom surface of the heating electrode to the upper surface of the diaphragm structure;
the second lead is positioned in the second heat insulation layer and is electrically connected with the heat detection electrode, and 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 positioned in the second heat insulation layer and is electrically connected with the gas detection electrode, and 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.
Further, the passivation layer comprises a first passivation layer and a second passivation layer;
The first passivation layer is positioned on the upper surface of the substrate, and the plane structure of the first passivation layer comprises the cross structure positioned in the middle and a frame for supporting the cross structure; the first passivation layer is made of silicon nitride, and the thickness of the first passivation layer is 100-500 nm;
the second passivation layer is positioned on the upper surface of the first passivation layer, and the plane structure of the second passivation layer corresponds to the plane structure of the first passivation layer; the second passivation layer is made of silicon dioxide, and the thickness of the second passivation layer is 100-500 nm.
In a second aspect, a method for preparing the MEMS micro-hotplate type gas sensor with the thermo-magnetic temperature measuring structure is disclosed, the method comprising the following steps:
1) A silicon wafer is selected as a substrate base material, the upper surface of the substrate base material is horizontal, the middle of the substrate base material is divided into a sensing area with a cross structure, the periphery of the sensing area is divided into a supporting area, and the supporting area is arranged 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 supporting area and the sensing area by photoetching and a low-pressure chemical vapor deposition method;
3) Preparing a first metal layer and a second metal layer on the upper surface of the second passivation layer through photoetching and magnetron sputtering, wherein the first metal layer and the second metal layer are used as a first adhesion area and a heating electrode, namely 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 insulation layer on the upper surface of the second passivation layer and around the heating electrode by photoetching and a low-pressure chemical vapor deposition method;
5) Preparing an alloy layer on the upper surfaces of the heating electrode and the first heat-insulating layer by photoetching and magnetron sputtering to serve as a permanent magnet film layer;
6) Preparing a first heat transfer insulating layer on the upper surfaces of the heating electrode, the first heat insulation insulating layer and the permanent magnet film layer by photoetching and a plasma enhanced chemical vapor deposition method;
7) Preparing a third metal layer on the upper surface of the first heat transfer insulating layer by photoetching and magnetron sputtering to serve as a heat detection electrode;
8) Preparing a second heat transfer insulating layer on the upper surfaces of the first heat transfer insulating layer and the heat detection electrode by photoetching and a plasma enhanced chemical vapor deposition method;
9) Preparing a fourth metal layer and a fifth metal layer on the upper surface of the second heat transfer insulating layer through photoetching and magnetron sputtering to serve as a second adhesion area and a gas detection electrode, namely, the gas detection electrode is fixedly arranged on the upper surface of the second heat transfer insulating layer through the second adhesion area;
10 Preparing a layer of gas-sensitive film on the upper surface of the gas detection electrode through photoetching and spin coating;
11 Preparing a second heat insulation layer on the upper surfaces of the first heat insulation layer and the second heat transfer insulation layer and around the gas detection electrode by photoetching and a plurality of times of low-pressure chemical vapor deposition methods;
12 Preparing a first lead area, a second lead area and a third lead area on the membrane structure by photoetching and dry etching the first thermal insulation layer and the second thermal insulation layer; the first lead, the second lead and the third lead which are prepared by laser pulse deposition are respectively arranged in corresponding lead areas to realize electrical connection;
13 And (3) etching the back of the substrate base material through photoetching and dry etching, and only reserving a frame corresponding to the supporting area to form the substrate to form a diaphragm structure so as to finish the preparation of the sensor.
According to the technical scheme, the following beneficial effects are achieved:
1. The invention utilizes the heat flow between the micro-heat plate and the gas-sensitive film in the gas sensor, reasonably utilizes the Nernst effect, realizes the accurate measurement of the temperature of the MEMS micro-heat plate type gas sensor, ensures the accurate control of the reaction temperature, ensures the reaction between the gas-sensitive film and the gas to be detected to be at the most proper temperature, and effectively improves the precision of the gas sensor; meanwhile, the invention can more accurately measure and control the required temperature of the MEMS micro-hot plate type gas sensing gas-sensitive film, thereby effectively improving the energy utilization rate.
2. In the invention, if the reaction temperature of the gas-sensitive film changes, heat flow is generated in the heat transfer layer formed by the first heat transfer insulating layer, the heat detection electrode and the second heat transfer insulating layer, and the heat detection electrode converts the temperature change into output voltage change under the action of the Nernst effect, so that the reaction temperature change of the gas-sensitive film can be monitored in real time, and the gas-sensitive film and the gas to be detected are accurately controlled to be always at the optimal reaction temperature.
3. The MEMS technology is adopted, a temperature measurement structure formed by a heating electrode, a permanent magnet film layer and a heat transfer layer are combined on the basis of the Nernst effect, and the micro-hotplate type gas sensor is monolithically integrated, so that the collaborative design is realized in the process; the volume of the MEMS micro-hotplate type gas sensor on the product is effectively reduced, and the MEMS micro-hotplate type gas sensor is suitable for a narrower space, so that the use scene is widened; in the whole, the MEMS micro-hotplate type gas sensor has the advantages of high precision, good consistency, easiness in batch manufacturing and low cost.
It should be understood that all combinations of the foregoing concepts, as well as additional concepts described in more detail below, may be considered a part of the inventive subject matter of the present disclosure as long as such concepts are not mutually inconsistent.
The foregoing and other aspects, embodiments, and features of the present teachings will be more fully understood from the following description, taken together with the accompanying drawings. Other additional aspects of the invention, such as features and/or advantages of the exemplary embodiments, will be apparent from the description which follows, or may be learned by practice of the embodiments according to the teachings of the invention.
Drawings
The drawings are not intended to be drawn to scale with respect to true references. In the drawings, each identical or nearly identical component that is illustrated in various figures may be represented by a like numeral. For purposes of clarity, not every component may be labeled in every drawing. Embodiments of various aspects of the invention will now be described, by way of example, with reference to the accompanying drawings, in which:
FIG. 1 is a schematic top view of a MEMS micro-hotplate gas sensor of the present disclosure;
FIG. 2 is a schematic cross-sectional view of a MEMS micro-hotplate gas sensor of the present disclosure taken along line A-A' of FIG. 1;
FIG. 3 is a schematic diagram showing a side structure corresponding to the structure of step 1) of the preparation method of the MEMS micro-hotplate type gas sensor disclosed by the invention;
FIG. 4 is a schematic diagram showing a planar structure corresponding to the structure of step 1) of the preparation method of the MEMS micro-hotplate type gas sensor disclosed by the invention;
FIG. 5 is a schematic diagram showing a side structure corresponding to a first passivation layer structure obtained in step 2) of the method for manufacturing a MEMS micro-hotplate type gas sensor according to the present invention;
FIG. 6 is a schematic diagram showing a planar structure corresponding to a first passivation layer structure obtained in step 2) of the method for preparing a MEMS micro-hotplate type gas sensor according to the present invention;
FIG. 7 is a schematic diagram showing a side structure corresponding to a second passivation layer structure obtained in step 2) of the method for manufacturing a MEMS micro-hotplate type gas sensor according to the present invention;
FIG. 8 is a schematic diagram showing a side structure corresponding to a second passivation layer structure obtained in step 2) of the method for manufacturing a MEMS micro-hotplate type gas sensor according to the present invention;
FIG. 9 is a schematic diagram showing a planar structure corresponding to a first adhesion layer structure of a first metal layer obtained in step 3) of the preparation method of the MEMS micro-hotplate type gas sensor disclosed by the invention;
FIG. 10 is a schematic diagram showing a side structure of a second metal layer as a heating electrode structure according to the MEMS micro-hotplate type gas sensor manufacturing method of the present invention in step 3);
FIG. 11 is a schematic diagram showing a side structure corresponding to the first insulating layer structure obtained in step 4) of the method for preparing the MEMS micro-hotplate type gas sensor disclosed by the invention;
FIG. 12 is a schematic diagram showing a side structure corresponding to a permanent magnet thin film layer structure obtained in step 5) of the MEMS micro-hotplate type gas sensor preparation method disclosed by the invention;
FIG. 13 is a schematic diagram showing a planar structure corresponding to the permanent magnetic thin film layer structure obtained in step 5) of the MEMS micro-hotplate type gas sensor preparation method disclosed by the invention;
FIG. 14 is a schematic diagram showing a side structure corresponding to the first heat transfer insulating layer structure obtained in step 6) of the preparation method of the MEMS micro-hotplate type gas sensor disclosed by the invention;
FIG. 15 is a schematic diagram showing a planar structure corresponding to the first heat transfer insulating layer structure obtained in step 6) of the preparation method of the MEMS micro-hotplate type gas sensor disclosed by the invention;
FIG. 16 is a schematic diagram showing a side structure of a third metal layer as a thermal detection electrode structure according to the MEMS micro-hotplate type gas sensor manufacturing method of the present invention in step 7);
FIG. 17 is a schematic diagram showing a side structure of a third metal layer corresponding to a thermal detection electrode structure prepared in step 7) of the preparation method of the MEMS micro-hotplate type gas sensor disclosed by the invention;
FIG. 18 is a schematic diagram showing a side structure of the MEMS micro-hotplate type gas sensor according to the present invention corresponding to the second heat transfer insulating layer structure prepared in step 8);
FIG. 19 is a schematic diagram showing a planar structure corresponding to the second heat transfer insulating layer structure obtained in step 8) of the method for preparing the MEMS micro-hotplate type gas sensor disclosed by the invention;
FIG. 20 is a schematic diagram showing a side structure of a fourth metal layer corresponding to a second adhesion layer structure obtained in step 9) of the method for manufacturing a MEMS micro-hotplate type gas sensor according to the present invention;
FIG. 21 is a schematic diagram showing a side structure of a fifth metal layer as a gas detection electrode structure according to step 9) of the method for manufacturing a MEMS micro-hotplate type gas sensor according to the present invention;
FIG. 22 is a schematic plan view showing a structure of a fifth metal layer as a gas detecting electrode according to the MEMS micro-hotplate type gas sensor manufacturing method of the present invention in step 9);
FIG. 23 is a schematic diagram showing a side structure corresponding to a structure of a gas-sensitive film prepared in step 10) of the preparation method of the MEMS micro-hotplate type gas sensor disclosed by the invention;
FIG. 24 is a schematic diagram showing a planar structure corresponding to the structure of a gas-sensitive film obtained in step 10) of the method for preparing a MEMS micro-hotplate type gas sensor according to the present invention;
FIG. 25 is a schematic diagram showing a side structure of a second insulating layer corresponding to the structure of FIG. 1 in the step 11) of the preparation method of the MEMS micro-hotplate type gas sensor disclosed by the invention;
FIG. 26 is a schematic diagram showing a planar structure corresponding to the second insulating layer structure obtained in step 11) of the method for manufacturing a MEMS micro-hotplate type gas sensor according to the present invention;
FIG. 27 is a schematic diagram showing a side structure corresponding to the structure obtained in step 12) of the method for manufacturing a MEMS micro-hotplate type gas sensor according to the present invention;
FIG. 28 is a schematic diagram showing a planar structure corresponding to the structure obtained in step 12) of the method for preparing a MEMS micro-hotplate type gas sensor according to the present invention;
In the figure, the specific meaning of each mark is as follows:
1a substrate; 2-a support region; 3-a sensing region; 4-a first passivation layer; 5-a second passivation layer; 6-a first adhesive zone; 7-heating the electrode; 8-a first thermal insulation layer; 9-a permanent magnet film layer; 10-a first heat transfer insulating layer; 11-a thermal detection electrode; 12-a second heat transfer insulating layer; 13-a second adhesive zone; 14-a gas detection electrode; 15-a gas sensitive film; 16-a second thermal insulation layer; 17-a first lead; 18-a second lead; 19-a third lead; 20-diaphragm structure.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. It will be apparent that the described embodiments are some, but not all, embodiments of the invention. All other embodiments, which can be made by a person skilled in the art without creative efforts, based on the described embodiments of the present invention fall within the protection scope of the present invention. Unless defined otherwise, technical or scientific terms used herein should be given the ordinary meaning as understood by one of ordinary skill in the art to which this invention belongs.
The terms "first," "second," and the like in the description and in the claims, are not used for any order, quantity, or importance, but are used for distinguishing between different elements. Also, unless the context clearly indicates otherwise, singular forms "a," "an," or "the" and similar terms do not denote a limitation of quantity, but rather denote the presence of at least one. The terms "comprises," "comprising," or the like are intended to cover a feature, integer, step, operation, element, and/or component recited as being present in the element or article that "comprises" or "comprising" does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. "up", "down", "left", "right" and the like are used only to indicate a relative positional relationship, and when the absolute position of the object to be described is changed, the relative positional relationship may be changed accordingly.
The MEMS micro-hotplate type gas sensor adopts a traditional temperature measurement mode, such as the use of a probe to contact a region to be measured or the use of the principles of thermocouples and thermal resistors to perform temperature measurement, the sensor has small size and low temperature measurement precision; meanwhile, the traditional contact measurement can cause the change of the temperature distribution of the sensor, so that the heat transfer efficiency of the micro-hotplate is reduced; in addition, because the gas-sensitive film needs to be contacted with the gas to be measured, the existing temperature measuring structure needs to touch the gas-sensitive film for measurement, if the gas-sensitive film is contacted for a long time, the area of a reaction interface between the gas-sensitive film and the gas to be measured is occupied, so that the reaction efficiency is reduced, and the reaction temperature of the gas sensor cannot be dynamically monitored in real time when the gas-sensitive film is contacted for a short time. Therefore, the MEMS micro-thermal plate type gas sensor with the thermo-magnetic temperature measuring structure and the preparation method thereof are provided, the thermo-magnetic temperature measuring structure is utilized to replace the traditional temperature measuring mode, the touch to the gas-sensitive film is not needed, and the precision and the sensitivity of the sensor can be further improved while the problems existing in the traditional temperature measuring mode are solved.
The MEMS micro-thermal plate type gas sensor with the thermo-magnetic temperature measuring structure and the preparation method thereof disclosed by the invention are further specifically described below with reference to the specific embodiments shown in the drawings.
As shown in fig. 1 and 2, the MEMS micro-thermal plate type gas sensor with a thermo-magnetic temperature measurement structure disclosed in the embodiment includes a substrate 1 and a diaphragm structure 20 disposed above the substrate 1.
As shown in the figure, the membrane structure 20 includes a passivation layer, a heating electrode 7, a permanent magnetic thin film layer 9, a first heat transfer insulating layer 10, a heat detecting electrode 11, a second heat transfer insulating layer 12, a gas detecting electrode 14 and a gas sensitive thin film 15, which are stacked from bottom to top; wherein the heating electrode 7 is used as a heat source, one path of heat flow generated by the heating electrode is transmitted to the sensing area 3 through the passivation layer, and the other path of heat flow is transmitted to the gas-sensitive film 15 through the first heat transfer insulating layer 10, the heat detection electrode 11 and the second heat transfer insulating layer 12; the gas-sensitive film 15 receives heat flow, heats the heat flow to a working temperature range, and changes self resistance after the heat flow and the gas to be detected undergo chemical reaction, and the gas detection electrode 14 detects the resistance and calculates and converts the resistance to obtain the concentration of the gas to be detected; the permanent magnetic film layer 9 generates a magnetic field when the MEMS micro-hotplate type 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 output voltage change based on the Nernst effect, so that the reaction temperature of the gas-sensitive film 15 is monitored in real time.
Optionally, the reasons for the reaction temperature change of the gas-sensitive film 15 in the application process of the MEMS micro-hotplate type gas sensor include, but are not limited to, the temperature change of the external environment of the sensor, the heating power change of the heating electrode, and the temperature change caused by the different chemical reaction processes of the gas-sensitive film and the gas to be measured.
Referring to fig. 3 to 28, the method for manufacturing the MEMS micro-hotplate type gas sensor with the thermo-magnetic temperature measurement structure is described in detail as follows.
1) A silicon wafer is selected as a substrate base material, the upper surface of the substrate base material is horizontal, the middle part of the substrate base material is divided into a sensing area 3 with a cross structure, the periphery of the sensing area 3 is divided into a supporting area 2, the supporting area 2 is arranged as a frame for supporting the cross structure, and the frame is arranged as a rectangular frame in the illustration;
the substrate is made of monocrystalline silicon with the thickness of 200-1000 μm, and the substrate 1 in fig. 3 is made of an N-type (100) silicon wafer with the thickness of 200 μm after etching. The sensing area 3 is a cross structure arranged in the middle of the upper surface of the substrate 1, so as to divide and locate each layer of the subsequent diaphragm structure 20, and the purpose of arranging each layer according to the cross structure in the sensor is to reduce unnecessary heat conduction, so as to reduce power consumption and improve response time. The purpose of the support area 2 and the sensing area 3 is to provide support for the fabrication of the diaphragm structure 20 in the initial stage, and the subsequent support area 2 provides lead-out space for the electrode leads of the sensor.
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 photoetching and a low-pressure chemical vapor deposition method;
The first passivation layer 4 is located on the upper surfaces of the support area 2 and the sensing area 3, and its planar structure corresponds to the cross structure of the frame of the support area 2 and the sensing area 3, as shown in fig. 5 and 6; the first passivation layer is made of silicon nitride, the thickness is 100-500 nm, and the thickness is 200nm in the embodiment;
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, as shown in fig. 7; the second passivation layer is made of silicon dioxide, and has a thickness of 100-500 nm, and in the embodiment, the thickness is selected to be 200nm.
3) Preparing a first metal layer and a second metal layer on the upper surface of the second passivation layer 5 through photoetching and magnetron sputtering, and taking the first metal layer and the second metal layer as a first adhesion area 6 and a heating electrode 7, namely, the heating electrode 7 is fixedly arranged on the upper surface of the second passivation layer 5 through the first adhesion area 6;
In the embodiment, the first metal layer is a metal titanium layer with the thickness of 100nm, which is formed on the upper surface of the second passivation layer 5 as the first adhesion region 6; the second metal layer is a first metal platinum layer with the thickness of 200nm, and is formed on the upper surface of the first adhesion area 6 to form a heating electrode 7; the planar structure of the heating electrode 7 corresponds to the transverse two arms and the central position of the cross structure of the sensing area 3; the heating electrode is arranged in a serpentine structure corresponding to the shape of a part of the planar structure in the center of the cross structure, and the wave crests and wave troughs of the serpentine structure extend towards the two longitudinal arm directions of the cross structure, as shown in fig. 10; in an embodiment the planar structure of the first adhesive area 6 is identical to the planar structure of the heater electrode 7, as shown in fig. 8 and 9.
The heating electrode 7 serves as a heat source and serves as a main structure of the micro-hotplate type gas sensor micro-hotplate for providing the optimal working temperature required by the reaction of the gas-sensitive film 15 with the gas to be measured. In addition, the middle plane shape of the heating electrode 7 is designed into a densely distributed snake-shaped structure, so that the purpose is to increase the heating resistance and the heating area, improve the heating efficiency and realize uniform heat transfer.
In order to maintain the heat insulation effect on the heating electrode 7, heat conduction between planes is reduced, and unnecessary heat loss is reduced; the membrane structure 20 further comprises a first insulating layer 8, which first insulating layer 8 can also serve as a supporting structure at the same time, avoiding deformation of the serpentine structure of the first adhesive zone 6 and the heater electrode 7 due to heating. So step 3) is completed to prepare the first heat-insulating layer 8 after the heating electrode 7 is prepared.
4) Preparing a first heat insulation layer 8 on the upper surface of the second passivation layer 5 and around the heating electrode 7 by photoetching and a low-pressure chemical vapor deposition method;
the first adhesive area 6 is fixedly arranged on the surface of the second passivation layer 5 based on the heating electrode 7, and the first heat-insulating layer 8 is simultaneously deposited around the first adhesive area 6; in an embodiment, the first insulating layer 8 is a silicon dioxide layer with a thickness of 300nm, the upper surface of which is flush with the upper surface of the heating electrode 7, and the portion thereof around the first adhesion zone 6 and the heating electrode 7 substantially fills the space of the serpentine structure, as shown in fig. 11.
5) Preparing an alloy layer on the upper surfaces of the heating electrode 7 and the first heat-insulating layer 8 by photoetching and magnetron sputtering to serve as a permanent magnet film layer 9;
The permanent magnetic film layer 9 is arranged on the upper surfaces of the heating electrode 7 and the first heat insulation layer 8, and the plane structure of the permanent magnetic film layer corresponds to the upper parts of four extension arms of the cross structure of the sensing area 3; the permanent magnetic film layer 9 is the same as the magnetic field required for providing the Nernst effect, and can be composed of FePt, coPt, coNiMnP or Sr ferrite with the thickness of 1-5 um; in the drawings, the permanent magnetic film layer 9 is composed of cobalt-platinum alloy with the thickness of 2um, and the specific position is shown in fig. 12 and 13.
6) Preparing a first heat transfer insulating 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 photoetching and a plasma enhanced chemical vapor deposition method;
The upper surface of the first heat transfer insulating layer 10 is horizontal, and the bottom of the first heat transfer insulating layer is arranged on the upper surfaces of the heating electrode 7, the first heat insulation layer 8 and the permanent magnetic film layer 9; in an example, the planar structure of the first heat transfer insulating layer corresponds to the cross structure of the sensing region 3, and has a thickness of 2.1-2.2 um, and is made of aluminum nitride, as shown in fig. 14 and 15; the first heat transfer insulating layer 10 is used in the sensor to transfer heat generated by the heater electrode 7 on the one hand, to generate a level of heat flow so that it can be heated more uniformly, and on the other hand to form an electrical isolation.
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 detecting electrode 11;
In an embodiment, the third metal layer is a metal copper layer with a thickness of 1um, so that the metal copper layer on the upper surface of the first heat transfer insulating layer 10 is used as the heat detecting electrode 11. The planar 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 planar structure of the heat detection electrode are respectively preset with electrode lead-out spaces for the heating electrode, as shown in fig. 16 and 17; the first heat transfer insulating layer 10 also serves to electrically isolate the heater electrode 7 from the heat detecting electrode 11.
When the sensor works, the permanent magnetic film layer 9 generates a magnetic field passing through the heat detection electrode 11 vertically, and the heat detection electrode 11 has heat flow transmitted to the four arms of the cross structure along the center thereof, so that based on the Nernst effect, electromotive force is generated on two sides of the heat detection electrode 11 perpendicular to the heat flow direction. In addition, because the cross structure of the heat detection electrode forms heat flow in four directions, four induced electromotive forces can be theoretically generated; the output value of the detection voltage can be increased through reasonable design of the circuit; and further, more accurate temperature measurement can be realized through mutual correction of induced potentials of all the branches.
Therefore, when the heating power of the heating electrode 7 is changed or the external ambient temperature is changed, a new heat flow is generated at the heat detecting electrode 11, thereby realizing real-time detection of the reaction temperature.
In addition, when the sensor is applied, a proper algorithm can be selected to solve a corresponding differential equation according to the output voltage of the thermal detection electrode 11, so as to obtain the temperature distribution condition of the whole heat transfer layer; therefore, the heating power of the heating electrode 7 can be adjusted according to the actually measured temperature, the accuracy of the sensor is improved, and the power consumption of the sensor is reduced.
8) Preparing a second heat transfer insulating layer 12 on the upper surfaces of the first heat transfer insulating layer 10 and the heat detecting electrode 11 by photolithography and a plasma enhanced chemical vapor deposition method;
The upper surface of the second heat transfer insulating layer 12 is horizontal, and the bottom of the second heat transfer insulating layer is arranged on the upper surfaces 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 100-300 nm, and the plane structure of the second heat transfer insulating layer corresponds to the cross structure of the sensing area 3; in an example, the second heat transfer insulating layer 12 having a thickness of 100nm is prepared by aluminum nitride deposition, as shown in fig. 18 and 19.
9) Preparing a fourth metal layer and a fifth metal layer on the upper surface of the second heat transfer insulating layer through photoetching and magnetron sputtering to serve as a second adhesion area and a gas detection electrode, namely, the gas detection electrode is fixedly arranged on the upper surface of the second heat transfer insulating layer through the second adhesion area;
In the embodiment, the fourth metal layer is a metal titanium layer with a thickness of 100nm, which is formed on the upper surface of the second heat transfer insulating layer 12 as the second adhesion region 13, as shown in fig. 20; the fifth metal layer is a second metal platinum layer with the thickness of 200nm formed on the upper surface of the second adhesion area 13, and the second metal platinum layer forms the gas detection electrode 14; namely, the gas detection electrode 14 is fixedly arranged on the upper surface of the second heat transfer insulating layer 12 by adopting the second adhesion area 13; the planar 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 in fig. 21 and 22, the shape of a part of the planar structure of the gas detection electrode 14 corresponding to the center of the cross structure is set into a comb tooth structure, and the comb tooth structures are staggered in opposite directions along the transverse two arms of the cross structure; the second heat transfer insulating layer 12 is used for electrically isolating the heat detecting electrode 11 from the gas detecting electrode 14, and the gas detecting electrode 14 is used for detecting electrical quantities, i.e. resistance values, of different areas of the gas sensitive film 15, so that the condition of uneven area reaction is eliminated to a certain extent, and the accuracy of the gas sensor is improved. In the embodiment, the planar structure of the second adhesion region 13 and the planar structure of the gas detection electrode 14 are the same.
10 Preparing a layer of gas-sensitive film 15 on the upper surface of the gas-detecting electrode 14 by photolithography and spin coating, as shown in fig. 23 and 24, the planar structure of the gas-sensitive film 15 corresponds to the planar structure of the gas-detecting electrode 14; the specific material and thickness of the gas-sensitive film 15 are determined by the gas to be measured, if the gas to be measured is ethanol gas, the Pt-doped SnO 2 can be selected, and the thickness is 5um.
In order to form electrical isolation among the heating electrode 7, the heat detection electrode 11 and the gas detection electrode 14 and form heat isolation between the first heat transfer insulating layer 10 and the outside, the diaphragm structure 20 is further provided with a second heat insulation insulating layer 16; thus, after the preparation of the gas-sensitive film 15 in step 10), the second heat-insulating layer 16 is prepared.
11 A second insulating layer 16 is formed on the upper surfaces of the first insulating layer 8, the second heat transfer insulating layer 12, and around the gas detection electrode 14 by photolithography and a plurality of low pressure chemical vapor deposition processes; the gas detection electrode 14 is fixedly arranged on the upper surface of the second heat transfer insulating layer 12 through the second adhesion area 13, so that the second heat insulation layer 16 is synchronously deposited around the second adhesion area 13 when being prepared, and the part of the second heat insulation layer, which is positioned around the second adhesion area 13 and the gas detection electrode 14, fully fills the gaps of the comb tooth structure.
As shown in fig. 25 and 26, the upper surface of the second heat insulating layer 16 is flush with the upper surface of the gas sensitive film 15, and the planar structure of the second heat insulating layer 16 corresponds to the cross structure of the support area 2 and the sensing area 3; in an example, the thickness of the second insulating layer 16 is 100nm, and the material is silicon dioxide.
In order to achieve an electrical connection of the whole of the membrane structure 20, the membrane structure 20 further comprises a first lead 17, a second lead 18 and a third lead 19, so that after the preparation of the second insulating layer 16 leads are introduced into the structure.
12 Preparing a first lead region, a second lead region and a third lead region on the diaphragm structure 20 by photolithography and dry etching the first and second thermal insulation layers 8 and 16, each lead exposing a corresponding electrode; placing the first lead 17, the second lead 18 and the third lead 19 prepared by laser pulse deposition in corresponding lead areas respectively to realize electrical connection; in an embodiment, the first lead 17, the second lead 18 and the third lead 19 are metal copper bars with sizes suitable for the sizes of corresponding lead areas, as shown in fig. 27 and 28; the first lead 17 is located in the first heat insulation layer 8 and the second heat insulation layer 16, and is electrically connected with the heating electrode 7, and the thickness of the first lead is the distance from the bottom surface of the heating electrode 7 to the upper surface of the membrane structure 20; the second lead 18 is located in the second insulating layer 16 and electrically connected to the heat detecting electrode 11, and has a thickness equal to a distance from the bottom surface of the heat detecting electrode 11 to the upper surface of the membrane structure 20; the third lead 19 is located in the second insulating layer 16 and electrically connected to the gas detecting electrode 14, and has a thickness equal to a distance from the bottom surface of the gas detecting electrode 14 to the upper surface of the membrane structure 20.
13 Etching the back of the substrate 1 by photoetching and dry etching, and only reserving a rectangular frame corresponding to the supporting area 2 to form the substrate 1 to form a diaphragm structure 20 so as to finish the preparation of the sensor; the planar structure of the final product is shown in fig. 1, and fig. 2 is a schematic cross-section along the direction A-A' in fig. 1, wherein the membrane structure 20 arranged on the upper surface of the substrate 1 is based on a cross structure in the middle of the first passivation layer 4.
The MEMS micro-thermal plate type gas sensor with the thermo-magnetic temperature measuring structure disclosed by the embodiment of the invention has the following working principle:
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 form a heat transfer layer of the MEMS micro-heat plate type gas sensor, and the whole heat transfer layer is of a cross structure; the heating electrode 7 serves as a heat source, and the heat flow generated by the heating electrode starts from the center of the cross structure, flows along the cross arm on one hand, and flows upwards to the gas-sensitive film 15 on the other hand, so that the temperature of the gas-sensitive film is raised. 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 film structure 20 jointly form a gas detection structure of the MEMS micro-hotplate type gas sensor; when the heating electrode (7) heats the gas-sensitive film 15 to a proper working temperature range, the gas-sensitive film 15 and the gas to be detected react chemically to change the resistance of the gas-sensitive film 15, the resistance is read out by the gas detection electrode (14), and the corresponding physical quantity, namely the concentration, of the gas to be detected is obtained through conversion of a corresponding algorithm. The heating electrode (7), the permanent magnet film layer (9) and the heat transfer layer in the film structure 20 jointly form a temperature detection structure of the MEMS micro-hotplate type gas sensor; when the permanent magnetic film layer (9) generates a magnetic field of the vertical heat transfer layer, based on the Nernst effect, electromotive force generated on two sides of the heat detection electrode (11) can obtain the temperature distribution of the whole heat transfer layer through a corresponding algorithm, so that the accurate measurement of temperature is realized; as long as the reaction temperature of the gas-sensitive film 15 changes (such as gas contact in a low-temperature environment), heat flow is formed in the heat transfer layer, and then the reaction temperature of the gas-sensitive film 15 can be measured in real time; and then the accuracy of the gas sensor can be further improved by correcting the heating power.
While the invention has been described with reference to preferred embodiments, it is not intended to be limiting. Those skilled in the art will appreciate that various modifications and adaptations can be made without departing from the spirit and scope of the present invention. Accordingly, the scope of the invention is defined by the appended claims.
Claims (12)
1. The MEMS micro-thermal plate type gas sensor with the thermo-magnetic temperature measuring structure is characterized by comprising a substrate and a diaphragm structure arranged above the substrate;
The membrane structure comprises a passivation layer, a heating electrode, a permanent magnet film layer, a first heat transfer insulating layer, a heat detection electrode, a second heat transfer insulating layer, a gas detection electrode and a gas-sensitive film which are arranged in a stacked manner from bottom to top; the heating electrode is used as a heat source, one path of heat flow generated by the heating electrode is transmitted to the sensing area through the passivation layer, and the other path of heat flow is transmitted to the gas-sensitive film through the first heat transfer insulating layer, the heat detection electrode and the second heat transfer insulating layer; the gas-sensitive film receives heat flow, heats the heat flow to a working temperature range, and changes self resistance after the heat flow and the gas to be detected undergo chemical reaction, and the heat flow is detected by the gas detection electrode and converted into the concentration of the gas to be detected; the permanent magnet film layer generates a magnetic field when the MEMS micro-hotplate type gas sensor is in a working state, and the thermal detection electrode converts the reaction temperature change of the gas-sensitive film into output voltage change based on the Nernst effect, so that the reaction temperature of the gas-sensitive film is monitored in real time.
2. The MEMS micro-hotplate gas sensor with a thermo-magnetic temperature measurement structure according to claim 1, wherein the passivation layer is disposed on the substrate, the middle of the passivation layer is horizontally disposed as a cross structure, and the outer periphery of the passivation layer is disposed as a frame for supporting the cross structure;
The heating electrode is fixedly arranged on the upper surface of the passivation layer, and the plane structure of the heating electrode corresponds to the transverse two arms and the central position of the cross structure; the heating electrode is arranged in a serpentine structure corresponding to the shape of a part of the planar structure in the center of the cross structure, and the wave crests and wave troughs of the serpentine structure extend towards the two longitudinal arm directions of the cross structure.
3. The MEMS micro-hotplate gas sensor with a thermo-magnetic temperature measurement structure of claim 2, wherein the diaphragm structure further comprises a first insulating layer;
the first heat-insulating layer is positioned on the upper surface of the passivation layer and around the heating electrode, the upper surface of the first heat-insulating layer is flush with the upper surface of the heating electrode, and the part of the first heat-insulating layer positioned around the heating electrode is used for fully filling the gap of the serpentine structure.
4. The MEMS micro-hotplate gas sensor with a thermo-magnetic temperature measurement structure according to claim 3, wherein the permanent magnetic thin film layer is disposed on the upper surface of the heating electrode and the first insulating layer, and the planar structure corresponds to the upper part 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 1-5 um.
5. The MEMS micro-hotplate gas sensor with a thermo-magnetic temperature measurement structure according to claim 4, wherein the upper surface of the first heat transfer insulating layer is horizontal, and the bottom is arranged on the upper surfaces of the heating electrode, the first heat insulation layer and the permanent magnetic thin film layer; the thickness of the first heat transfer insulating layer is 2.1-2.2 um, and the plane structure of the first heat transfer insulating layer corresponds to the cross structure; the first heat transfer insulating layer is used for generating horizontal heat flow while transferring heat.
6. The MEMS micro-hotplate gas sensor with a thermo-magnetic temperature measurement structure of claim 5, wherein the thermal detection electrode is disposed on the upper surface of the first heat transfer insulating layer; the plane structure of the thermal detection electrode corresponds to the cross structure;
Electrode leading-out spaces for the heating electrodes are respectively preset at the tail ends of the four extension arms on the plane structure of the heat detection electrode;
the permanent magnetic film layer is used for generating a magnetic field vertically passing through the heat detection electrode, and the heat detection electrode is provided with heat flow which is transmitted to the four arms of the cross structure along the center of the heat detection electrode, so that based on the Nernst effect, electromotive force is generated on two sides of the heat detection electrode, which are vertical to the heat flow direction;
The first heat transfer insulating layer is used for forming electric isolation between the heating electrode and the thermal detection electrode.
7. The MEMS micro-hotplate gas sensor with a thermo-magnetic temperature measurement structure of claim 6, wherein the upper surface of the second heat transfer insulating layer is horizontal and the bottom is arranged on the upper surfaces of the first heat transfer insulating layer and the heat detection electrode; the thickness of the second heat transfer insulating layer is 100-300 nm, and the plane structure of the second heat transfer insulating layer corresponds to the cross structure.
8. The MEMS micro-hotplate gas sensor with thermo-magnetic temperature measurement structure according to claim 7, wherein the gas detection electrode is fixed on the upper surface of the second heat transfer insulating layer, and the planar structure corresponds to the two longitudinal arms and the central position of the cross structure; the shape of the part of the plane structure of the gas detection electrode corresponding to the center of the cross structure is set to be a comb tooth structure, and the comb tooth structure is staggered in opposite directions along the two transverse arm directions of the cross structure and is used for detecting the electric quantity of different areas of the gas-sensitive film;
The gas-sensitive film is positioned above the gas detection electrode, and the plane structure of the gas-sensitive film corresponds to the gas detection electrode;
The second heat transfer insulating layer is used for forming electric isolation between the thermal detection electrode and the gas detection electrode.
9. The MEMS micro-hotplate gas sensor with a thermo-magnetic temperature measurement structure of claim 8, wherein the diaphragm structure further comprises a second insulating layer;
The second heat insulation layer is positioned on the first heat insulation layer and the second heat transfer insulation layer, the upper surface of the second heat insulation layer is flush with the upper surface of the gas-sensitive film, and the plane structure of the second heat insulation layer corresponds to the frame and the cross structure; the second heat-insulating layer is used for forming electric isolation among the heating electrode, the heat detection electrode and the gas detection electrode, and is used for simultaneously forming heat isolation between the second heat-transfer insulating layer and the outside.
10. The MEMS micro-hotplate gas sensor with a thermo-magnetic temperature measurement structure of claim 9, wherein the diaphragm structure further comprises a first lead, a second lead, and a third lead;
The first lead is positioned in the first heat insulation layer and the second heat insulation layer, is electrically connected with the heating electrode, and has the thickness of the distance from the bottom surface of the heating electrode to the upper surface of the diaphragm structure;
the second lead is positioned in the second heat insulation layer and is electrically connected with the heat detection electrode, and 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 positioned in the second heat insulation layer and is electrically connected with the gas detection electrode, and 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 thermo-magnetic temperature measurement structure of claim 2, wherein the passivation layer comprises a first passivation layer and a second passivation layer;
The first passivation layer is positioned on the upper surface of the substrate, and the plane structure of the first passivation layer comprises the cross structure positioned in the middle and a frame for supporting the cross structure; the first passivation layer is made of silicon nitride, and the thickness of the first passivation layer is 100-500 nm;
the second passivation layer is positioned on the upper surface of the first passivation layer, and the plane structure of the second passivation layer corresponds to the plane structure of the first passivation layer; the second passivation layer is made of silicon dioxide, and the thickness of the second passivation layer is 100-500 nm.
12. The method for manufacturing a MEMS micro-hotplate gas sensor with a thermo-magnetic temperature measurement structure according to any of claims 1-11, comprising the steps of:
1) A silicon wafer is selected as a substrate base material, the upper surface of the substrate base material is horizontal, the middle of the substrate base material is divided into a sensing area with a cross structure, the periphery of the sensing area is divided into a supporting area, and the supporting area is arranged 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 supporting area and the sensing area by photoetching and a low-pressure chemical vapor deposition method;
3) Preparing a first metal layer and a second metal layer on the upper surface of the second passivation layer through photoetching and magnetron sputtering, wherein the first metal layer and the second metal layer are used as a first adhesion area and a heating electrode, namely 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 insulation layer on the upper surface of the second passivation layer and around the heating electrode by photoetching and a low-pressure chemical vapor deposition method;
5) Preparing an alloy layer on the upper surfaces of the heating electrode and the first heat-insulating layer by photoetching and magnetron sputtering to serve as a permanent magnet film layer;
6) Preparing a first heat transfer insulating layer on the upper surfaces of the heating electrode, the first heat insulation insulating layer and the permanent magnet film layer by photoetching and a plasma enhanced chemical vapor deposition method;
7) Preparing a third metal layer on the upper surface of the first heat transfer insulating layer by photoetching and magnetron sputtering to serve as a heat detection electrode;
8) Preparing a second heat transfer insulating layer on the upper surfaces of the first heat transfer insulating layer and the heat detection electrode by photoetching and a plasma enhanced chemical vapor deposition method;
9) Preparing a fourth metal layer and a fifth metal layer on the upper surface of the second heat transfer insulating layer through photoetching and magnetron sputtering to serve as a second adhesion area and a gas detection electrode, namely, the gas detection electrode is fixedly arranged on the upper surface of the second heat transfer insulating layer through the second adhesion area;
10 Preparing a layer of gas-sensitive film on the upper surface of the gas detection electrode through photoetching and spin coating;
11 Preparing a second heat insulation layer on the upper surfaces of the first heat insulation layer and the second heat transfer insulation layer and around the gas detection electrode by photoetching and a plurality of times of low-pressure chemical vapor deposition methods;
12 Preparing a first lead area, a second lead area and a third lead area on the membrane structure by photoetching and dry etching the first thermal insulation layer and the second thermal insulation layer; the first lead, the second lead and the third lead which are prepared by laser pulse deposition are respectively arranged in corresponding lead areas to realize electrical connection;
13 And (3) etching the back of the substrate base material through photoetching and dry etching, and only reserving a frame corresponding to the supporting area to form the substrate to form a diaphragm structure so as to finish the preparation of the sensor.
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