MEMS gas sensor

Abstract

The utility model provides an MEMS gas sensor, the MEMS gas sensor comprises a silicon substrate, a support layer, a heating element, an isolation layer, a test element and a gas sensitive element, the silicon substrate comprises a front surface and a back surface deviating from the front surface, the front surface is provided with a heat insulation cavity, the back surface is provided with a hollow heat collection cavity, the heat insulation cavity is communicated with the heat collection cavity, and the heat collection cavity is communicated with the support layer. The silicon substrate further comprises a first cavity wall and a second cavity wall which are opposite to each other; the supporting layer is connected between the first cavity wall and the second cavity wall and located in the heat insulation cavity, and the supporting layer isolates the heat insulation cavity from the heat collection cavity. The heating element is arranged on the supporting layer and located in the heat insulation cavity. The isolation layer covers the supporting layer and the heating element, and the isolation layer is parallel to the supporting layer; the test element is arranged on one surface of the isolation layer deviating from the heating element; the gas-sensitive element is arranged on one side of the test element away from the isolation layer.

Description

Technical Field

[0001] This application relates to the technical field of gas detection, and particularly to a MEMS gas sensor. Background Art

[0002] Medical detection often performs non-invasive and safe detection of the human body by detecting corresponding indicators through the exhaled gas of the human body. In the prior art, semiconductor metal oxide MEMS gas sensors are often used to detect the exhaled gas of the human body. Semiconductor metal oxides require a micro-heating platform to enable the sensitive material to work at an appropriate temperature. The micro-heating platform can be divided into a suspended membrane type and a closed membrane type according to different types of support membrane structures.

[0003] However, the suspended membrane type MEMS gas sensor has low mechanical strength, is easy to break, and has low stability due to the need for the support of support beams. In addition, the manufacturing process of the suspended membrane type MEMS gas sensor from a silicon wafer to a gas sensor is complex, and the yield of the finished product is low. Moreover, when manufacturing the cavity of the suspended membrane type MEMS gas sensor, the production of an additional mask is required, which not only increases the cost of the MEMS gas sensor but also increases the power consumption due to the easy appearance of silicon islands under the support beams due to the corrosion angle when manufacturing the cavity. For the closed membrane type MEMS gas sensor, the micro-heating platform has excessive heat dissipation, resulting in a large power loss of the MEMS gas sensor. Summary of the Utility Model

[0004] This application provides a MEMS gas sensor, which can improve the mechanical strength of the MEMS gas sensor, reduce its power loss, and reduce the volume of the components therein.

[0005] In a first aspect, an embodiment of this application provides a MEMS gas sensor, which includes a silicon substrate, a support layer, a heating element, an isolation layer, a test element, and a gas-sensitive element. The silicon substrate includes a front surface and a back surface facing away from the front surface. The front surface is provided with a heat insulation cavity, and the back surface is provided with a hollow heat accumulation cavity. The heat insulation cavity and the heat accumulation cavity are communicated. The silicon substrate further includes a first cavity wall and a second cavity wall opposite to the heat insulation cavity. The support layer is connected between the first cavity wall and the second cavity wall and is located in the heat insulation cavity, and the support layer isolates the heat insulation cavity and the heat accumulation cavity. The heating element is disposed on the support layer and is located in the heat insulation cavity. The isolation layer covers the support layer and covers the heating element, and the isolation layer is parallel to the support layer. The test element is disposed on a surface of the isolation layer facing away from the heating element. The gas-sensitive element is disposed on a surface of the test element facing away from the isolation layer.

[0006] Preferably, the depth of the heat insulation cavity is less than the depth of the heat accumulation cavity.

[0007] Preferably, the support layer is composed of a silicon oxide layer and a silicon nitride layer obtained by depositing a silicon oxide thin film and a silicon nitride thin film respectively. The silicon oxide layer is close to the heat accumulation cavity, the silicon nitride layer is located on the side of the silicon oxide layer facing away from the heat accumulation cavity, and the heating element is arranged on the side of the silicon nitride layer facing away from the silicon oxide layer.

[0008] Preferably, the silicon substrate further includes a third cavity wall and a fourth cavity wall oppositely arranged between the first cavity wall and the second cavity wall of the heat insulation cavity, and the support layer is also connected between the third cavity wall and the fourth cavity wall.

[0009] Preferably, the MEMS gas sensor is provided with an electrode for providing energy for the normal operation of the MEMS gas sensor. The support layer includes a first support portion for supporting the heating element, and a second support portion and a third support portion respectively connected to both sides of the first support portion close to the first cavity wall and the second cavity wall. The electrodes are provided on the sides of the second support portion and the third support portion facing away from the first support portion.

[0010] Preferably, the second support portion and the third support portion are also connected between the third cavity wall and the fourth cavity wall and are located in the heat insulation cavity.

[0011] Preferably, when the electrodes are arranged on the sides of the second support portion and the third support portion facing away from the first support portion, the sides of the electrodes facing away from the first support portion do not protrude from the front surface.

[0012] Preferably, the isolation layer has a certain gap from the second support portion and the third support portion respectively.

[0013] Preferably, the electrodes include a heating element electrode and a test element electrode. The heating element electrode is provided with an electrode connection portion accommodated in the gap so that the heating element is electrically connected to the heating element through the electrode connection portion, and the test element electrode is sleeved on the electrode connection portion and is electrically connected to the test element.

[0014] Preferably, the isolation layer is formed by depositing the silicon nitride thin film.

[0015] The above MEMS gas sensor is provided with a heat insulation cavity and a heat accumulation cavity on the front and back of the silicon substrate respectively. A support layer connected to the cavity wall of the heat insulation cavity is provided in the heat insulation cavity to connect to the silicon substrate, and a heating element, an isolation layer, a test element and a gas-sensitive element are arranged in sequence in the direction of the support layer facing the front, so that other components of the MEMS gas sensor can be stably arranged in the heat insulation cavity. While improving the mechanical strength of the MEMS gas sensor, the heat insulation cavity can slow down the heat dissipation of the heat generated by the heating element caused by heat convection, and the heat accumulation cavity can accumulate more heat generated by the heating element in the support layer, thereby reducing the power loss of the MEMS gas sensor. In addition, the heat insulation cavity and the heat accumulation cavity are fabricated by deep silicon etching process and inductively coupled plasma etching process, which saves the manufacturing cost. The volume of the device is also reduced by the setting method of the heating element electrode and the test element electrode, thereby reducing the space occupied by the electrodes. Brief Description of the Drawings

[0016] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on the structures shown in these drawings.

[0017] Figure 1 It is a cross-sectional view of the MEMS gas sensor provided by the embodiment of the present application.

[0018] Figure 2 It is a perspective view of the MEMS gas sensor provided by the embodiment of the present application.

[0019] Each component label

[0020] MEMS gas sensor 10 Silicon nitride layer 22

[0021] Silicon substrate 1 First support portion 23

[0022] Heat insulation cavity 11 Second support portion 24

[0023] First cavity wall 111 Third support portion 25

[0024] Second cavity wall 112 Heating element 3

[0025] Third cavity wall 113 Isolation layer 4

[0026] Fourth cavity wall 114 Test element 5

[0027] Heat accumulation cavity 12 Gas-sensitive element 6

[0028] Top surface 13, electrode 7

[0029] Bottom surface 14, heating element electrode 71

[0030] Support layer 2, electrode connection part 711

[0031] Silicon oxide layer 21, test element electrode 72

[0032] The realization of the purpose of this application, functional features and advantages will be further described in conjunction with the embodiments and with reference to the accompanying drawings. Detailed implementation manners

[0033] In the description of the present utility model, it should be understood that the orientation or positional relationships indicated by the terms "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. are based on the orientation or positional relationships shown in the drawings. These are only for the convenience of describing the present utility model and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as a limitation of the present utility model.

[0034] In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present utility model, "a plurality" means two or more unless otherwise specifically defined.

[0035] In the present utility model, unless otherwise clearly specified and defined, the terms "installed", "connected", "connected to", "fixed", etc. should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or integrated; it may be a mechanical connection or an electrical connection; it may be directly connected or indirectly connected through an intermediate medium, and it may be the internal communication of two elements or the interaction relationship between two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present utility model can be understood according to specific circumstances.

[0036] To make the content of the present utility model clearer and more accurate, it will be described in detail below in conjunction with the accompanying drawings. The accompanying drawings of the specification show examples of the embodiments of the present utility model, where the same reference numerals represent the same elements. It can be understood that the scale shown in the accompanying drawings of the specification is not the actual implementation scale of the present utility model. It is only for the purpose of schematic illustration and is not drawn according to the original size.

[0037] Please refer to Figure 1, which is a cross-sectional view of the MEMS gas sensor provided by the embodiment of the present application. The present application provides a MEMS gas sensor 10, which can improve the mechanical strength of the MEMS gas sensor 10, reduce the power loss of the MEMS gas sensor 10, and at the same time reduce the volume of the components in the MEMS gas sensor 10. The specific features of each component in the MEMS gas sensor 10 will be elaborated in detail below.

[0038] Please refer to Figure 1 and Figure 2 , the MEMS gas sensor 10 includes a silicon substrate 1, a support layer 2, a heating element 3, an isolation layer 4, a test element 5, and a gas-sensitive element 6. The silicon substrate 1 is generally in the shape of a cuboid. The silicon substrate 1 includes a front surface 13 and a back surface 14 facing away from the front surface 13. Among them, a heat insulation cavity 11 is provided on the front surface 13, and the heat insulation cavity 11 is used to reduce the loss of heat convection. A hollow heat accumulation cavity 12 is provided on the back surface 14, and the heat accumulation cavity 12 is used to accumulate the heat dissipated by heat conduction in the MEMS gas sensor 10. The heat insulation cavity 11 and the heat accumulation cavity 12 are communicated. The silicon substrate 1 further includes a first cavity wall 111 and a second cavity wall 112 disposed opposite to the heat insulation cavity 11. The present application reduces the power loss of the MEMS gas sensor 10 during operation through the heat insulation cavity 11 and the heat accumulation cavity 12.

[0039] In this embodiment, the support layer 2 is connected between the first cavity wall 111 and the second cavity wall 112 and is located in the heat insulation cavity 11 to enhance the mechanical strength of the MEMS gas sensor 10 while supporting the MEMS gas sensor 10. The support layer 2 isolates the heat insulation cavity 11 and the heat accumulation cavity 12. Among them, the support layer 2 is composed of a silicon oxide layer 21 and a silicon nitride layer 22 respectively deposited by a silicon oxide thin film and a silicon nitride thin film. The silicon oxide layer 21 is close to the heat accumulation cavity 12. The silicon nitride layer 22 is located on the side of the silicon oxide layer 21 facing away from the heat accumulation cavity 12. Among them, the thickness of the silicon oxide layer 21 is 500 - 700 nm. The thickness of the silicon nitride layer 22 is 1300 - 1500 nm. In the present application, the depth of the heat insulation cavity 11 is formed from the front surface 13 to the side of the support layer 2 facing the front surface 13, and the depth of the heat accumulation cavity 12 is formed from the back surface 14 to the side of the support layer 2 facing the back surface 14. The depth of the heat insulation cavity 11 is less than the depth of the heat accumulation cavity 12. Preferably, the depth of the heat insulation cavity 11 is 5 - 20 um. The depth of the heat accumulation cavity 12 is 300 - 600 um.

[0040] Furthermore, the silicon substrate 1 further includes a third cavity wall 113 and a fourth cavity wall 114 disposed opposite to the heat insulation cavity 11 between the first cavity wall 111 and the second cavity wall 112. The support layer 2 is also connected between the third cavity wall 113 and the fourth cavity wall 114, that is, the first cavity wall 111, the third cavity wall 113, the second cavity wall 112, and the fourth cavity wall 114 are sequentially connected to enclose the heat insulation cavity 11.

[0041] In some feasible embodiments, the support layer 2 is also composed of a silica layer 21 and two silicon nitride layers 22 obtained by depositing a silica thin film and a silicon nitride thin film. Among them, the silica layer 21 is located between the two silicon nitride layers 22. One of the two silicon nitride layers 22 is located on the side of the silica layer 21 facing the heating element 3, and the other is located on the side of the silica layer 21 facing the heat accumulation cavity 12.

[0042] In some other feasible embodiments, the support layer 2 can also be made of other materials with low thermal conductivity, such as polyimide, to reduce the heat loss caused by heat conduction in the MEMS gas sensor 10.

[0043] In this embodiment, the heating element 3 is disposed on the support layer 2 and is located within the heat insulation cavity 11, that is, the heating element 3 is disposed on the side of the silicon nitride layer 22 facing away from the silica layer 21. The material of the heating element 3 includes but is not limited to tungsten, polysilicon, platinum, etc. The heating element 3 of the heating wire includes but is not limited to circular, S-shaped, loop-shaped, etc. Preferably, the thickness of the heating element 3 is 100 - 500 nm.

[0044] In this embodiment, the isolation layer 4 is formed by depositing a silicon nitride thin film. The isolation layer 4 covers the support layer 2 and covers the heating element 3. In this application, the isolation layer 4 is parallel to the support layer 2, that is, the support layer 2 and the isolation layer 4 are arranged in parallel. The test element 5 is disposed on the side of the isolation layer 4 facing away from the heating element 3. The test element 5 is used to obtain corresponding preset indicators according to the gas sensed by the gas sensing element 6, such as the composition of the exhaled gas, the respiratory spectrum reflected by the exhaled gas, etc. The material of the test element 5 includes but is not limited to platinum, palladium, etc. The shape of the test element 5 includes but is not limited to interdigital electrodes, strips, interdigital triple electrodes, etc. The thickness of the test element 5 is 100 - 500 nm, that is, the thickness of the heating element 3 and the test element 5 can be equal or unequal. The gas sensing element 6 is used to sense gas. The gas sensing element 6 is disposed on the side of the test element 5 facing away from the isolation layer 4.

[0045] In this embodiment, the support layer 2 includes a first support portion 23 for supporting the heating element 3, and a second support portion 24 and a third support portion 25 respectively connected to two sides of the first support portion 23 close to the first cavity wall 111 and the second cavity wall 112. The MEMS gas sensor 10 is provided with an electrode 7 for providing energy for the normal operation of the MEMS gas sensor 10. Electrodes 7 are provided on the sides of the second support portion 24 and the third support portion 25 facing away from the first support portion 23. The second support portion 24 and the third support portion 25 are also connected between the third cavity wall 113 and the fourth cavity wall 114 and are located within the heat insulation cavity 11. When the electrode 7 is disposed on the side of the second support portion 24 and the third support portion 25 facing away from the first support portion 23, the side of the electrode 7 facing away from the first support portion 23 does not protrude beyond the front surface 13 to reduce the size of the MEMS gas sensor 10.

[0046] Furthermore, the isolation layer 4 has a certain gap from the second support portion 24 and the third support portion 25 respectively. The electrode 7 includes a heating element electrode 71 and a test element electrode 72. Among them, the heating element electrode 71 is provided with an electrode connection portion 711 disposed in the gap, so that the heating element electrode 71 is electrically connected to the heating element 3 through the electrode connection portion 711. The test element electrode 72 is sleeved on the electrode connection portion 711 and electrically connected to the test element 5 to reduce the device size of the MEMS gas sensor 10. The test element 5 obtains a preset index according to the gas under the energy provided by the test element electrode 72. The heating element 3 generates heat under the energy provided by the heating element electrode 71 to make the gas-sensitive element 6 and the test element 5 have a certain temperature, so as to improve the sensitivity of the gas-sensitive element 6 and the test element 5, and further improve the sensing efficiency of the MEMS gas sensor 10. Next, how the MEMS gas sensor 10 is fabricated will be specifically described.

[0047] First, an insulating cavity 11 is etched from the front side to the back side of the silicon substrate 1. Specifically, an inductively coupled plasma-reactive ion etching (ICP-RIE) process can be used to etch the silicon substrate from the front side 13 to the back side 14 to form the insulating cavity 11. The depth of the insulating cavity 11 is 5 - 20 μm. In this application, a silicon-on-insulator (SOI), that is, an SOI wafer, can also be used to replace the silicon substrate 1 for etching the insulating cavity 11 to reduce the manufacturing process of silicon dioxide in the ICP-RIE process. Among them, the insulating cavity 11 includes a first cavity wall 111 and a second cavity wall 112 arranged oppositely. The insulating cavity 11 further includes a third cavity wall 113 and a fourth cavity wall 114 arranged oppositely between the first cavity wall 111 and the second cavity wall 112. When etching the insulating cavity 11 on the front side 13 of the silicon substrate 1, accommodating members (not shown in the figure) for accommodating the electrode 7 are also etched at positions outside the insulating cavity 11 and on both sides close to the first cavity wall 111 and the second cavity wall 112 respectively, so that the electrode 7 does not protrude from the front side 13 in the MEMS gas sensor 10, thereby reducing the size of the MEMS gas sensor 10.

[0048] After etching and forming a thermal insulation cavity 11 on a silicon substrate 1, a silicon oxide thin film and a silicon nitride thin film are alternately deposited in the thermal insulation cavity 11 to sequentially form a silicon oxide layer 21 and a silicon nitride layer 22 to form a support layer 2, and the support layer 2 is connected to a first cavity wall 111 and a second cavity wall 112. Specifically, a plasma enhanced chemical vapor deposition (PECVD) process and a low pressure chemical vapor deposition (LPCVD) process can be used to alternately deposit a silicon oxide thin film and a silicon nitride thin film in the thermal insulation cavity 11 to form a silicon oxide layer 21 and a silicon nitride layer 22, and then form a support layer 2. Among them, the silicon nitride layer 22 is located on the side of the thermal insulation cavity 11 facing the front surface 13, and the silicon oxide layer 21 is located on the side of the silicon nitride layer 22 away from the front surface 13, that is, the support layer 2 is sequentially the silicon oxide layer 21 and the silicon nitride layer 22 from the thermal insulation cavity 11 to the front surface 13. The thickness of the silicon oxide layer 21 is 500 - 700 nm. The thickness of the silicon nitride layer 22 is 1300 - 1500 nm. In this application, a silicon oxide thin film and a silicon nitride thin film are also alternately deposited in the thermal insulation cavity 11 and the accommodating member to form a first support portion 23 located in the thermal insulation cavity 11, and a second support portion 24 and a third support portion 25 respectively connected to both sides of the first support portion 23 close to the first cavity wall 111 and the second cavity wall 112. The second support portion 24 and the third support portion 25 are used to arrange electrodes 7.

[0049] Subsequently, a heating element 3 is prepared in the thermal insulation cavity 11 and arranged on the support layer 2. Specifically, a magnetron sputtering process and a lift-off process can be used to prepare the heating element 3 on the support layer 2. Among them, the thickness of the heating element 3 is 100 - 500 nm. The material of the heating element 3 includes but is not limited to gold, platinum, tungsten, polysilicon, etc. The shape of the heating element 3 includes but is not limited to an S shape, a loop shape, a circular shape, an elliptical shape, etc. At the same time, corresponding heating element electrodes 71 are respectively provided on the second support portion 24 and the third support portion 25, and the heating element 3 is electrically connected to the heating element electrodes 71.

[0050] Next, a silicon nitride thin film is deposited on the side of the support layer 2 facing the front surface 13 and the side of the heating element 3 facing the front surface 13 to form an isolation layer 4, so that the isolation layer 4 covers the support layer 2 and covers the heating element 3. Specifically, a PECVD process can be used to deposit a silicon nitride thin film on the side of the support layer 2 facing the front surface 13 and the side of the heating element 3 facing the front surface 13 to form an isolation layer 4. The thickness of the isolation layer 4 is 300 - 500 nm. The isolation layer 4 has a certain gap with the second support portion 24 and the third support portion 25 respectively. The heating element electrode 71 is provided with an electrode connection portion 711 accommodated in the gap, so that the heating element 3 is electrically connected to the heating element electrode 71 through the electrode connection portion 711. And there is a certain height difference between the heating element 3 and the heating element electrode 71, which can reduce the vertical height when the isolation layer 4 covers the heating element 3, and further reduce the material loss of the MEMS gas sensor 10.

[0051] After the isolation layer 4 is formed by deposition, a test element 5 is fabricated on the side of the isolation layer 4 facing away from the heating element 3. Specifically, the test element 5 can be fabricated on the side of the isolation layer 4 facing away from the heating element 3 by using a magnetron sputtering process and a lift-off technique process. Among them, the material of the test element 5 includes but is not limited to gold, platinum, palladium, etc. The thickness of the test element 5 is 100 - 500 nm. Preferably, the thickness of the test element 5 is 100 - 300 nm. The shape of the test element 5 includes but is not limited to interdigital electrodes, single electrodes, interdigital electrodes with a three-electrode structure, etc. At the same time, corresponding test element electrodes 72 are respectively provided on the second support portion 24 and the third support portion 25, and the test element 5 is electrically connected to the test element electrodes 72. Among them, the test element electrodes 72 are sleeved on the electrode connection portion 711.

[0052] After the test element 5 is fabricated, a gas-sensitive element 6 is fabricated on the side of the test element 5 facing away from the isolation layer 4. Specifically, the gas-sensitive element 6 can be fabricated on the side of the test element 5 facing away from the isolation layer 4 by using a magnetron sputtering process, so that the gas-sensitive element 6 covers the test element 5. Among them, the material of the gas-sensitive element 6 includes but is not limited to tin dioxide, zinc oxide, etc.

[0053] Finally, a heat accumulation cavity 12 is etched from the back surface 14 to the front surface 13 of the silicon substrate 1, so that the support layer 2 isolates the heat insulation cavity 11 and the heat accumulation cavity 12. Specifically, a deep silicon etching process can be used to etch from the back surface 14 to the front surface 13 to form the heat accumulation cavity 12, thereby completing the fabrication of the MEMS gas sensor 10. Among them, the depth of the heat accumulation cavity 12 is 300 - 600 μm, that is, the depth of the heat accumulation cavity 12 is greater than the depth of the heat insulation cavity 11.

[0054] In the above embodiments, by providing a heat insulation cavity and a heat accumulation cavity on the front and back surfaces of the silicon substrate respectively, a support layer connected to the cavity wall of the heat insulation cavity is provided in the heat insulation cavity to connect to the silicon substrate, and a heating element, an isolation layer, a test element, and a gas-sensitive element are sequentially arranged in the direction of the support layer facing the front surface, so that other components of the MEMS gas sensor can be stably arranged in the heat insulation cavity. While improving the mechanical strength of the MEMS gas sensor, the heat insulation cavity can slow down the heat dissipation of the heat generated by the heating element due to heat convection, and the heat accumulation cavity can accumulate more heat generated by the heating element in the support layer, thereby reducing the power loss of the MEMS gas sensor. In addition, the heat insulation cavity and the heat accumulation cavity are fabricated by using a deep silicon etching process and an inductively coupled plasma etching process, saving the manufacturing cost, and also reducing the volume of the device by the setting method of the heating element electrode and the test element electrode, thereby reducing the space occupied by the electrode.

[0055] Obviously, those skilled in the art can make various modifications and variations to the present utility model without departing from the spirit and scope of this application. Thus, provided that these modifications and variations of the present utility model fall within the scope of the claims of the present utility model and its equivalent technologies, the present utility model is also intended to include these modifications and variations.

[0056] The above are only the preferred embodiments of the present utility model listed, and of course, the scope of the rights of the present utility model cannot be limited thereby. Therefore, equivalent changes made according to the claims of the present utility model still fall within the scope covered by the present utility model.

Claims

1. A MEMS gas sensor, characterized in that: The MEMS gas sensor comprises: A silicon substrate, comprising a front side and a back side away from the front side, wherein the front side is provided with a heat-insulating cavity, the back side is provided with a hollow heat-collecting cavity, the heat-insulating cavity is connected with the heat-collecting cavity, and the silicon substrate further comprises a first cavity wall and a second cavity wall arranged opposite to the heat-insulating cavity; A support layer, connected between the first cavity wall and the second cavity wall and located in the heat-insulating cavity, and the support layer isolates the heat-insulating cavity from the heat-collecting cavity; A heating element, disposed on the support layer and located in the heat insulation cavity; An isolation layer, covering the support layer and the heating element, wherein the isolation layer is parallel to the support layer; a test element, disposed on a side of the isolation layer facing away from the heating element; and The gas sensor is arranged on a side of the test element away from the isolation layer.

2. The MEMS gas sensor according to claim 1, characterized in that: The depth of the heat insulation cavity is less than the depth of the heat collection cavity.

3. The MEMS gas sensor according to claim 1, characterized in that: The support layer is composed of a silicon oxide layer and a silicon nitride layer obtained by depositing a silicon oxide film and a silicon nitride film respectively. The silicon oxide layer is close to the heat focusing cavity, and the silicon nitride layer is located on the side of the silicon oxide layer away from the heat focusing cavity. The heating element is arranged on the side of the silicon nitride layer away from the silicon oxide layer.

4. The MEMS gas sensor according to claim 3, characterized in that: The silicon substrate further includes a third cavity wall and a fourth cavity wall of the heat-insulating cavity which are arranged between the first cavity wall and the second cavity wall, and the supporting layer is further connected between the third cavity wall and the fourth cavity wall.

5. The MEMS gas sensor according to claim 4, characterized in that: The MEMS gas sensor is provided with an electrode for providing energy for the normal operation of the MEMS gas sensor. The supporting layer includes a first supporting portion for supporting the heating element, and a second supporting portion and a third supporting portion respectively connected to both sides of the first supporting portion close to the first cavity wall and the second cavity wall. The second supporting portion and the third supporting portion are provided with the electrode on one side facing away from the first supporting portion.

6. The MEMS gas sensor according to claim 5, characterized in that: The second supporting portion and the third supporting portion are also connected between the third cavity wall and the fourth cavity wall and are located in the heat insulation cavity.

7. The MEMS gas sensor according to claim 6, characterized in that: When the electrode is disposed on a surface of the second supporting portion and the third supporting portion away from the first supporting portion, a surface of the electrode away from the first supporting portion does not protrude from the front surface.

8. The MEMS gas sensor according to claim 5, characterized in that: The isolation layer has a certain gap with the second supporting part and the third supporting part respectively.

9. The MEMS gas sensor according to claim 8, characterized in that: The electrode comprises a heating element electrode and a testing element electrode. The heating element electrode is provided with an electrode connecting portion accommodated in the gap so that the heating element is electrically connected to the heating element through the electrode connecting portion. The testing element electrode is sleeved on the electrode connecting portion and electrically connected to the testing element.

10. The MEMS gas sensor according to claim 3, characterized in that: The isolation layer is formed by depositing the silicon nitride film.

Images