MEMS (Micro Electro Mechanical System) gas sensor with polymer reinforcing structure and manufacturing method

Abstract

The invention discloses an MEMS (Micro Electro Mechanical System) gas sensor with a polymer reinforcing structure and a manufacturing method. The structural design is reinforced through the flexible polymer, the overall structural strength of the sensor is maintained through the rigid frame, and meanwhile the flexible supporting layer is introduced, so that mechanical stress is effectively dispersed, vibration energy is absorbed, micro-strain of the sensitive film is remarkably reduced, and film layer breakage or signal drifting is avoided. And compared with a pure flexible structure, the rigidity is obviously improved, and the long-term stability of the sensor in a dynamic environment can be ensured. And the process is compatible with a standard MEMS production line, the critical dimension control precision reaches + / -0.2 [mu] m, the flexible polymer reinforced structure support design can reduce connection bridge fracture caused by stress in the preparation process, and the yield of mass production is further improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of MEMS gas sensors, and in particular relates to a MEMS gas sensor with a polymer reinforced structure and a manufacturing method thereof. Background Art

[0002] With the rapid development of industrial intelligence and the Internet of Things (IoT), demand for gas sensors has surged in areas such as environmental monitoring, industrial safety, and healthcare. Microelectromechanical system (MEMS) gas sensors, with their small size, high sensitivity, and low power consumption, hold broad application prospects in these areas.

[0003] Traditional MEMS gas sensors achieve miniaturization and high sensitivity through the integration of micromechanical structures and semiconductor processes, but their core structures mostly adopt a single rigid structure support design, which makes it difficult to balance mechanical stability and environmental adaptability.

[0004] For example, existing MEMS gas sensors are often based on silicon- or silicon oxide-based rigid support structures. These structures are susceptible to stress concentration, leading to rupture of sensitive membranes or performance degradation in complex environments (such as vibration, shock, or temperature fluctuations). Furthermore, these rigid support structures struggle to effectively mitigate the microstrain effects of external mechanical interference on sensitive materials, thereby reducing the sensor's long-term stability and measurement accuracy.

[0005] For example, Wang Mei et al. (Wang Mei, Wang Xudan, Jiang Liying, MEMS Micro-hotplate Structural Design and Simulation, Transducer and Microsystem Technologies, Vol. 43, No. 10, 2024) proposed several suspended micro-hotplate designs and used finite element analysis (FEA) to simulate the micro-hotplates in terms of thermal stability, mechanical stability, power consumption, and efficiency at 400°C, a common operating temperature for gas sensors. The results showed that the spiral micro-hotplate had better overall performance. Furthermore, they optimized several factors that may affect the performance of the micro-hotplate, such as electrode voltage, support layer thickness, and microheater line width-to-spacing ratio, to obtain the micro-hotplate pattern and parameter design with the best overall performance.

[0006] Yang Guang (Yang Guang, Research on Design and Process of Micro-hotplates for MEMS Gas Sensors, Master's Thesis of Huazhong University of Science and Technology, 2022) designed MEMS micro-hotplates with different structures and revealed their different thermal properties. Eleven types of micro-hotplates with different structures or material applications were proposed, and corresponding application scenarios were recommended for devices with different thermal properties. For example, large working area devices and silicon nitride substrate devices are used in precious metal catalytic gas sensing applications that require uniform heating; when using narrow cantilever MEMS micro-hotplates, wedge-shaped gas-sensitive material deposition areas are used to maximize the thermal performance of the MEMS micro-hotplate. The design idea of adding rounded corners to global corners to improve the local mechanical properties of the MEMS micro-hotplate was proposed and applied. Therefore, there is an urgent need for a new sensor support structure that has both mechanical stability and environmental adaptability. Summary of the Invention

[0007] To address the aforementioned deficiencies in the prior art, the present invention provides a MEMS micro-hotplate gas sensor structure with a polymer reinforcement structure and a supporting manufacturing method. This structure utilizes organic polymers (PI, PSPI) as a flexible support layer combined with a silicon oxide / silicon nitride dielectric layer to form a polymer-reinforced support structure, improving the sensor's structural stability, robust anti-interference capabilities, and long-term reliability. This can further expand its high-end application needs in industrial safety, smart wearables, and vehicle-mounted detection.

[0008] The present invention first provides a method for manufacturing a MEMS gas sensor with a polymer reinforced structure, comprising the following steps:

[0009] (1) providing a substrate;

[0010] (2) preparing a first dielectric layer on a substrate;

[0011] (3) preparing a heating electrode layer on the first dielectric layer, the heating electrode layer having a heating electrode and a heating electrode pad;

[0012] (4) preparing a second dielectric layer on the heating electrode layer and in the gaps between the heating electrodes;

[0013] (5) preparing a measuring electrode layer on the second dielectric layer, wherein the measuring electrode layer has a measuring electrode and a measuring electrode pad;

[0014] (6) Etching a release window on the periphery of the working area where the heating electrode and the measuring electrode are located, and further etching the substrate below the working area to release the working area to form a suspended structure;

[0015] (7) loading a gas-sensitive material on the surface of the measuring electrode layer in the working area to form a gas-sensitive material layer;

[0016] The manufacturing method further includes preparing a flexible supporting layer, and the flexible supporting layer is prepared in any of the following ways: on the surface of the measuring electrode layer, below the first dielectric layer, between the first dielectric layer and the heating electrode, or between the second dielectric layer and the measuring electrode, and the step of preparing the flexible supporting layer corresponds to the location.

[0017] Preferably, the substrate is made of at least one of single crystal silicon, ceramic, porous silicon or silicon nitride;

[0018] The dielectric material used in the first dielectric layer is at least one of silicon oxide or silicon nitride;

[0019] The dielectric material used in the second dielectric layer is at least one of silicon oxide or silicon nitride;

[0020] The electrode material used in the heating electrode layer is at least one of platinum, gold, tungsten or molybdenum;

[0021] The electrode material used in the measuring electrode layer is at least one of platinum, gold, tungsten, molybdenum or aluminum;

[0022] The flexible supporting material used in the flexible supporting layer is at least one of polyimide or photosensitive polyimide;

[0023] The gas-sensitive material used in the gas-sensitive material layer is at least one of tin oxide, tungsten oxide or zinc oxide.

[0024] Preferably, the thickness of the substrate is 300-600 μm;

[0025] The thickness of the first dielectric layer is 500 nm-3 μm;

[0026] The thickness of the second dielectric layer is 50 nm-1 μm;

[0027] The thickness of the heating electrode layer is 30-300 nm;

[0028] The thickness of the measuring electrode layer is 30-300 nm;

[0029] The thickness of the flexible supporting layer is 1-2 μm;

[0030] The thickness of the gas-sensitive material layer is greater than 50 nanometers.

[0031] Further preferably, the thickness of the gas-sensitive material layer is 50 nm-2 μm.

[0032] Preferably, the method for preparing the first dielectric layer in step (2) is plasma enhanced chemical vapor deposition, low pressure chemical vapor deposition or thermal oxidation;

[0033] The method for preparing the heating electrode layer in step (3) is sputtering or evaporation;

[0034] The method for preparing the second dielectric layer in step (4) is plasma enhanced chemical vapor deposition, low pressure chemical vapor deposition or thermal oxidation;

[0035] The method for preparing the measuring electrode layer in step (5) is sputtering or evaporation;

[0036] The method for preparing the gas-sensitive material layer in step (7) is thin film growth, dripping, printing or sputtering deposition.

[0037] Preferably, the method for preparing the flexible support layer is: spin coating the flexible support material, patterning the flexible support material using a photolithography process, removing unnecessary areas, and leaving a patterned flexible support layer structure.

[0038] Preferably, in step (3), a first adhesion layer is grown on the surface of the first dielectric layer before preparing the heating electrode layer;

[0039] Before preparing the second dielectric layer in step (4), a second adhesion layer is first grown on the heating electrode layer;

[0040] Before preparing the measuring electrode layer in step (5), a third adhesion layer is first grown on the second dielectric layer.

[0041] Further preferably, the material of each of the first adhesion layer, the second adhesion layer and the third adhesion layer is selected from at least one of aluminum oxide and titanium;

[0042] The thickness of each of the first adhesive layer, the second adhesive layer, and the third adhesive layer is 5-10 nm.

[0043] Preferably, in step (6), the working area is first covered with a photoresist to protect it, and the first dielectric layer and the second dielectric layer of the protective area outside the working area that is not covered by the photoresist are removed by dry etching to form a release window, and the release window is further used to etch away the second dielectric layer and a part of the thickness of the substrate below the working area, so that the working area is released to form a suspended structure.

[0044] The present invention also provides a MEMS gas sensor with a polymer reinforcement structure manufactured by the manufacturing method.

[0045] Compared with the prior art, the present invention has the following beneficial effects:

[0046] Compared with the purely rigid structure in the existing technology, which is easily affected by thermal cycle fatigue and stress, the present invention adopts a flexible polymer reinforced structural design, uses a rigid frame to maintain the overall structural strength of the sensor, and introduces a flexible support layer, thereby effectively dispersing mechanical stress and absorbing vibration energy, significantly reducing the micro-strain of the sensitive film, and avoiding film rupture or signal drift. Compared with the purely flexible structure, its stiffness is significantly improved, which can ensure the long-term stability of the sensor in a dynamic environment. In addition, the process is compatible with standard MEMS production lines, and the key dimension control accuracy reaches ±0.2μm. The flexible polymer reinforced structural support design can reduce the breakage of the connecting bridge caused by stress during the preparation process, and further improve the mass production yield to.

[0047] Through collaborative innovation in structure, materials and processes, this invention overcomes the reliability bottleneck of traditional sensors in complex environments, while taking into account high performance and low cost, providing technical support for the large-scale application of MEMS gas sensors in harsh scenarios such as automotive electronics and industrial Internet of Things. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 Schematic diagram of the cross section of the substrate.

[0049] Figure 2 This is a cross-sectional schematic diagram of completing the first dielectric layer in step 2 of the MEMS gas sensor preparation method.

[0050] Figure 3 This is a cross-sectional schematic diagram of the MEMS gas sensor preparation method after the heating electrode is completed in step 3.

[0051] Figure 4 This is a cross-sectional schematic diagram of completing the second dielectric layer in step 4 of the MEMS gas sensor preparation method.

[0052] Figure 5 This is a cross-sectional schematic diagram after the measurement electrode is completed in step 5 of the MEMS gas sensor preparation method.

[0053] Figure 6 This is a cross-sectional diagram of the MEMS gas sensor fabrication method after the release window is etched in step 6.

[0054] Figure 7 This is a cross-sectional schematic diagram after the flexible support layer is prepared in step 7 of the MEMS gas sensor preparation method.

[0055] Figure 8 This is a cross-sectional schematic diagram of the device structure after process release is completed in step 8 of the MEMS gas sensor preparation method.

[0056] Figure 9 This is a cross-sectional schematic diagram after the gas-sensitive material is loaded in step 9 of the MEMS gas sensor preparation method.

[0057] Reference numerals: 1: substrate; 2: first dielectric layer; 3: heating electrode layer; 4: second dielectric layer; 5: measuring electrode layer; 6: flexible supporting layer; 7: gas-sensitive material layer; 8: cavity area. DETAILED DESCRIPTION

[0058] like Figures 1-9 As shown, the present invention provides a MEMS micro-hotplate gas sensor with a polymer reinforcement structure and a manufacturing method. The cross-sectional positions shown in the structures shown in each step of the figure may be different, so the areas of the same layer structure in the upper and lower steps may be different. The preparation method includes the following steps:

[0059] Step 1: Provide a substrate 1, which is made of single crystal silicon, ceramic, porous silicon or silicon nitride. The thickness of the substrate 1 is 300-600 μm. Figure 1 A schematic cross-sectional view of the substrate.

[0060] Step 2: A first dielectric layer 2 is formed on the surface of substrate 1 by plasma-enhanced chemical vapor deposition (PECVD), low-pressure chemical vapor deposition (LPCVD), or thermal oxidation. This layer serves as both a dielectric layer and a support layer. The first dielectric layer 2 can be made of silicon oxide, silicon nitride, or other dielectric materials. The thickness of the first dielectric layer 2 is 500 nm to 3 μm. Figure 2 FIG. 1 is a schematic cross-sectional view of the completed first dielectric layer 2 .

[0061] Step 3: A 5-10 nm thick layer of aluminum oxide or titanium is grown on the surface of the first dielectric layer 2 by sputtering or evaporation as a first adhesion layer. A heater electrode layer 3 is also formed on the surface of the first adhesion layer by sputtering or evaporation. The heater electrode layer 3 comprises heater electrodes and corresponding pads. The heater electrodes and pads are made of at least one of platinum, tungsten, and molybdenum. Alternatively, the heater electrode pads may be coated with gold. The heater electrodes have two pads. The thickness of the heater electrode layer 3 is 30-300 nm. Figure 3 This is a cross-sectional diagram of the completed heating electrode, in which the first adhesion layer is not drawn.

[0062] Step 4: To improve adhesion, a 5-10 nm thick second adhesion layer is sputtered onto the surface of the heater electrode layer 3. A second adhesion layer made of aluminum oxide or titanium is used. A second dielectric layer 4 is deposited on the surface of the second adhesion layer using PECVD, LPCVD, or thermal oxidation. This serves as both a dielectric layer and a support layer. The second dielectric layer 4 can be made of silicon oxide, silicon nitride, or other dielectric materials. The thickness of the second dielectric layer 4 is 50 nm to 1 μm. The thickness of the second dielectric layer 4 is calculated based on the thickness above the heater electrode layer 3 and does not take into account the thickness of the gap between the electrodes. Figure 4 To complete the cross-sectional schematic diagram of the second dielectric layer 4 , the second adhesive layer is not drawn in the figure.

[0063] Step 5: A 5-10 nm thick layer of aluminum oxide or titanium is grown on the surface of the second dielectric layer 4 by magnetron sputtering or electron beam evaporation as a third adhesion layer. A measuring electrode layer 5 is then sputtered or evaporated onto the surface of the third adhesion layer. The measuring electrode layer 5 comprises measuring electrodes and corresponding pads. The electrodes and pads are made of at least one of platinum, gold, tungsten, molybdenum, and aluminum. The measuring electrode pads can also be coated with gold. The measuring electrodes have two pads. The thickness of the measuring electrode layer 5 is 30-300 nm. The pads corresponding to the heating electrodes do not overlap with the pads corresponding to the measuring electrodes. Figure 5 This is a cross-sectional diagram of the completed measuring electrode; the third adhesion layer is not shown in the figure.

[0064] Step 6: Use photoresist to cover the protective measuring electrodes and heating electrodes, the central heating area (the area where the curved winding structure of the heating electrode is located), and the area used to form the support structure (the support structure refers to the beam structure that ultimately connects the heating plate of the suspension structure and the peripheral PAD). This exposes the heating electrode PAD, the central area where the suspension will later be formed, and the remaining areas of dielectric material that need to be removed. Use dry etching to remove the dielectric material in the exposed area, exposing the heating electrode pad PAD while leaving a certain dielectric support structure (i.e., two layers of dielectric layers). Figure 6 Schematic cross-section after etching in preparation for completing the release window.

[0065] Step 7: Prepare a flexible support layer 6 on the surface of the measuring electrode layer 5, and process the surface of the flexible support layer 6 to leave a PAD area and a gas-sensitive material loading area. The method for preparing the flexible support layer 6 is: spin-coating the flexible support material, patterning the flexible support material using a photolithography process, removing unnecessary areas, and leaving a patterned flexible support layer structure. The material of the flexible support layer 6 is an organic high molecular polymer PI (polyimide) or PSPI (photosensitive polyimide), and the thickness of the flexible support layer 6 is 1-2μm. PI or PSPI materials are flexible, high temperature resistant, compatible with MEMS processes, and are photosensitive materials that can be micro-nano processed and can be patterned by photolithography. Figure 7 This is a cross-sectional schematic diagram after the flexible support layer is prepared.

[0066] Step 8: Etch the material (substrate) below the working area to release the working area on the upper surface to form a suspended structure. The suspended structure is a beam-type suspended structure, supported and connected by bridges, which are not shown in the figure. Figure 8 Schematic diagram of the cross-section of the device structure after process release.

[0067] Step 9: A gas-sensitive material layer 7 is deposited on the surface of the measuring electrode layer 5 by thin-film growth, dripping, printing, or sputtering deposition. The material of the gas-sensitive material layer 7 is tin oxide, tungsten oxide, zinc oxide, or other gas-sensitive materials, or a combination of at least two materials. The thickness of the gas-sensitive material layer 7 is generally above 50 nanometers, with no upper limit. This thickness can be flexibly varied based on the process, materials, and gas without affecting the sensing effect. The preferred thickness is 50 nm to 2 μm. The thickness of the gas-sensitive material layer 7 is based on the thickness above the measuring electrode layer 5, and the thickness of the gap between the electrodes is not taken into account.

[0068] The gas sensitive material covers the surface of the measuring electrode and fills the gap in the middle of the measuring electrode. During operation, effective electrical signals can be collected through the measuring electrode. Figure 9 This is a cross-sectional schematic diagram after the gas-sensitive material is loaded.

[0069] The heating electrode layer 3 and the measuring electrode layer 5 respectively include heating electrodes and measuring electrodes, as well as their corresponding PADs. The pads are mainly arranged in the four edge areas of the device, and the heating area and test area are respectively arranged in the central area of each layer on the device.

[0070] Furthermore, the first and second dielectric layers are etched simultaneously using the etching window. This single etching process exposes the pad window for the second heater electrode, removes the dielectric material outside the front working area, and retains a certain support structure. This approach reduces the number of etching steps, saving costs. Furthermore, the method is simple, has a high yield rate, and is suitable for large-scale mass production.

[0071] Furthermore, the flexible supporting layer 6 is not limited to being on the surface of the measuring electrode layer, but can also be placed below the first dielectric layer, between the first dielectric layer and the heating electrode, or between the second dielectric layer and the measuring electrode. The position of the process layer is relatively flexible.

[0072] Example 1

[0073] Step 1: Substrate 1 is 500 μm thick. <100> Crystal orientation single crystal silicon.

[0074] Step 2: Prepare a first dielectric layer 2 on the surface of the substrate 1:

[0075] First, the surface of the single crystal silicon is thermally oxidized to form a first dielectric layer 2 with a thickness of 500 nm, which serves as a dielectric layer and a support layer. The material of the first dielectric layer 2 is silicon oxide.

[0076] Step 3: Prepare a second layer of heating electrodes and corresponding pads on the surface of the support layer (first dielectric layer 2):

[0077] A 5nm layer of aluminum oxide is sputtered onto the surface of the first dielectric layer 2 as an adhesion layer. A 30nm thick heater electrode layer 3, representing the platinum metal layer of the heater electrode, is then grown on top. Photolithography is used to pattern the photoresist to form the heater electrode and corresponding PAD patterns. Etching is then used to remove excess platinum and aluminum oxide, forming a complete heater electrode and corresponding pad.

[0078] Step 4: Prepare a second dielectric layer 4 on the surface of the heating electrode layer 3 to serve as a dielectric layer and a support layer:

[0079] In order to improve adhesion, a 5nm thick second adhesion layer is sputtered on the wafer surface. The second adhesion layer uses aluminum oxide. A layer of silicon oxide is deposited on the aluminum oxide surface by vapor deposition as the second dielectric layer 4. Its thickness is 50nm.

[0080] Step 5: Prepare a measuring electrode layer 5 on the surface of the second dielectric layer 4:

[0081] The measuring electrode layer 5 comprises measuring electrodes and corresponding pads. The fabrication process for the measuring electrodes is essentially the same as that for the heating electrodes. A 5nm layer of aluminum oxide is grown on the wafer surface using magnetron sputtering as a third adhesion layer. A 30nm thick platinum layer for the measuring electrodes is then sputtered. The measuring electrodes and corresponding pads are patterned using photolithography. Excess platinum and aluminum oxide are then etched away, forming complete measuring electrodes and corresponding pads.

[0082] Step 6: Remove the silicon oxide outside the effective electrode area (the area covered by the electrode and PAD pattern):

[0083] When making the photolithography mask for this step, it is necessary to expose the position of the heating electrode layer pad while protecting the heating and measuring electrodes. At the same time, a certain silicon oxide structure needs to be left to ensure that the pad window of the heating electrode in the heating electrode layer 3 is exposed after etching is completed, and the silicon oxide outside the front working area is removed to ensure the stability of the suspended electrode area after the process is completed.

[0084] Step 7: Prepare a flexible support layer 6 on the surface of the measuring electrode layer 5:

[0085] The PI layer material is spin-coated on the entire wafer surface, and the PI is exposed and patterned using a method similar to photolithography. Excess material is removed by cleaning, leaving the PAD area and the central gas-sensitive material loading area. The thickness of the flexible support layer 6 is 1 μm.

[0086] Step 8: Etch the silicon substrate to form a cavity area 8, so that the working area is suspended:

[0087] The silicon substrate is etched by a wet etching process to form a cavity region 8. The existence of the cavity region 8 enables the working area to form a suspended structure.

[0088] Step 9: Prepare a gas-sensitive material layer 7 on the surface of the measuring electrode layer 5 to cover the gap between the measuring electrodes:

[0089] A thin-film process is used to grow a gas-sensitive material layer 7, made of tin oxide. This material covers the surface of the measuring electrodes and fills the gaps between them, allowing the electrodes to collect effective electrical signals during operation. The thickness of this layer is 50 nm.

[0090] Example 2

[0091] Step 1: Select a 500μm thick substrate <100> Crystal orientation single crystal silicon.

[0092] Step 2: Prepare a first dielectric layer on the substrate surface:

[0093] First, a first dielectric layer with a thickness of 3 μm is formed on the surface of the single crystal silicon using plasma enhanced chemical vapor deposition (PECVD), which serves as a dielectric layer and a support layer. The material of the first dielectric layer is silicon nitride.

[0094] Step 3: Prepare a flexible supporting layer on the surface of the first dielectric layer:

[0095] The PI layer is spin-coated across the entire wafer surface and patterned using a process similar to photolithography. Excess material is removed through cleaning, leaving the PAD area and the central gas-sensing material loading area. The thickness of the flexible support layer is 2μm.

[0096] Step 4: Prepare heating electrodes and corresponding pads on the surface of the flexible support layer:

[0097] A 10nm thick titanium layer is grown on the wafer surface by evaporation as an adhesion layer. A 300nm thick platinum layer, the heater electrode, is then grown on top. Photolithography is used to pattern the photoresist to form the heater electrode and corresponding PAD patterns. Etching is then used to remove the excess platinum and titanium, leaving the heater electrode and corresponding pads intact.

[0098] Step 5: Prepare a second dielectric layer on the surface of the heating electrode layer to serve as a dielectric layer and a support layer:

[0099] In order to increase adhesion, a 10nm second adhesion layer needs to be sputtered on the wafer surface. The second adhesion layer uses aluminum oxide, and a layer of silicon nitride is deposited on the aluminum oxide surface by vapor deposition as the second dielectric layer with a thickness of 1μm.

[0100] Step 6: Prepare a measuring electrode layer on the surface of the second dielectric layer:

[0101] The measuring electrode layer consists of measuring electrodes and corresponding pads. The fabrication process for the measuring electrodes is essentially the same as that for the heating electrodes. A 10nm thick layer of titanium is grown on the wafer surface using electron beam evaporation as a third adhesion layer. A 300nm thick platinum layer for the measuring electrodes is then sputtered. The measuring electrodes and corresponding pads are patterned using photolithography. Excess platinum and titanium are then etched away, forming the complete measuring electrodes and corresponding pads.

[0102] Step 7: Remove the silicon nitride outside the effective electrode area (the area covered by the electrode and PAD pattern):

[0103] When making the photolithography mask for this step, it is necessary to expose the position of the heating electrode layer pad while protecting the heating and measuring electrodes. At the same time, a certain silicon nitride structure needs to be left to ensure that the pad window of the heating electrode in the heating electrode layer is exposed after etching is completed, and the silicon nitride outside the front working area is removed to ensure the stability of the suspended electrode area after the process is completed.

[0104] Step 8: Etch the silicon substrate to form a cavity area, so that the working area is suspended:

[0105] The silicon substrate is etched by a wet etching process to form a cavity region. The existence of the cavity region enables the working area to form a suspended structure.

[0106] Step 9: Prepare a gas-sensitive material layer on the surface of the measuring electrode layer to cover the gap between the measuring electrodes:

[0107] A thin-film process is used to grow a gas-sensitive material layer made of zinc oxide. This material covers the surface of the measuring electrodes and fills the gaps between them, allowing the measuring electrodes to collect effective electrical signals during operation. The thickness of the gas-sensitive material layer 7 is 2 μm.

[0108] In the above-mentioned MEMS gas sensor chip structure, the structure of the first dielectric layer and the second dielectric layer retained after etching is the rigid support, and the structure left after the flexible support material is patterned is the flexible support. The rigid dielectric layer forms a frame based on a silicon-based process. Its high rigidity can effectively constrain thermal expansion deformation under high-temperature operation and prevent the suspension structure from displacement or fracture due to thermal stress. The flexible support layer uses polymer materials and is integrated through a patterning process. Its low elastic modulus can actively absorb external mechanical vibration or impact energy, greatly reducing the risk of stress concentration in dynamic environments. The anchor area of the rigid frame and the flexible layer is cross-linked to form a composite support system. The collaborative support structure between the two can effectively improve the strength of the suspension structure, so that the sensor exhibits excellent fatigue resistance in long-term cyclic operation, providing a highly stable microenvironmental foundation for gas detection. At the same time, it is compatible with large-scale manufacturing processes and can significantly improve the reliability and service life of the device.

Claims

1. A method for manufacturing a MEMS gas sensor having a polymer reinforced structure, characterized in that: The following steps are involved: (1) providing a substrate; (2) preparing a first dielectric layer on a substrate; (3) preparing a heating electrode layer on the first dielectric layer, the heating electrode layer having a heating electrode and a heating electrode pad; (4) preparing a second dielectric layer on the heating electrode layer and in the gaps between the heating electrodes; (5) preparing a measuring electrode layer on the second dielectric layer, wherein the measuring electrode layer has a measuring electrode and a measuring electrode pad; (6) Etching a release window on the periphery of the working area where the heating electrode and the measuring electrode are located, and further etching the substrate below the working area to release the working area to form a suspended structure; (7) loading a gas-sensitive material on the surface of the measuring electrode layer in the working area to form a gas-sensitive material layer; The manufacturing method further includes preparing a flexible supporting layer, and the flexible supporting layer is prepared in any of the following ways: on the surface of the measuring electrode layer, below the first dielectric layer, between the first dielectric layer and the heating electrode, or between the second dielectric layer and the measuring electrode, and the step of preparing the flexible supporting layer corresponds to the location.

2. The method for manufacturing a MEMS gas sensor with a polymer reinforcement structure according to claim 1, characterized in that: The substrate is made of at least one of single crystal silicon, ceramic, porous silicon or silicon nitride; The dielectric material used in the first dielectric layer is at least one of silicon oxide or silicon nitride; The dielectric material used in the second dielectric layer is at least one of silicon oxide or silicon nitride; The electrode material used in the heating electrode layer is at least one of platinum, gold, tungsten or molybdenum; The electrode material used in the measuring electrode layer is at least one of platinum, gold, tungsten, molybdenum or aluminum; The flexible supporting material used in the flexible supporting layer is at least one of polyimide or photosensitive polyimide; The gas-sensitive material used in the gas-sensitive material layer is at least one of tin oxide, tungsten oxide or zinc oxide.

3. The method for manufacturing a MEMS gas sensor with a polymer reinforcement structure according to claim 1, characterized in that: The thickness of the substrate is 300-600 μm; The thickness of the first dielectric layer is 500 nm-3 μm; The thickness of the second dielectric layer is 50 nm-1 μm; The thickness of the heating electrode layer is 30-300 nm; The thickness of the measuring electrode layer is 30-300 nm; The thickness of the flexible supporting layer is 1-2 μm; The thickness of the gas-sensitive material layer is greater than 50 nanometers.

4. The method for manufacturing a MEMS gas sensor with a polymer reinforcement structure according to claim 3, characterized in that: The thickness of the gas-sensitive material layer is 50 nm-2 μm.

5. The method for manufacturing a MEMS gas sensor with a polymer reinforcement structure according to claim 1, wherein: The method for preparing the first dielectric layer in step (2) is plasma enhanced chemical vapor deposition, low pressure chemical vapor deposition or thermal oxidation; The method for preparing the heating electrode layer in step (3) is sputtering or evaporation; The method for preparing the second dielectric layer in step (4) is plasma enhanced chemical vapor deposition, low pressure chemical vapor deposition or thermal oxidation; The method for preparing the measuring electrode layer in step (5) is sputtering or evaporation; The method for preparing the gas-sensitive material layer in step (7) is thin film growth, dripping, printing or sputtering deposition.

6. The method for manufacturing a MEMS gas sensor with a polymer reinforcement structure according to claim 1, wherein: The method for preparing the flexible support layer is: spin coating the flexible support material, patterning the flexible support material using a photolithography process, removing unnecessary areas, and leaving a patterned flexible support layer structure.

7. The method for manufacturing a MEMS gas sensor with a polymer reinforcement structure according to claim 1, wherein: In step (3), a first adhesion layer is grown on the surface of the first dielectric layer before preparing the heating electrode layer; Before preparing the second dielectric layer in step (4), a second adhesion layer is first grown on the heating electrode layer; Before preparing the measuring electrode layer in step (5), a third adhesion layer is first grown on the second dielectric layer.

8. The method for manufacturing a MEMS gas sensor with a polymer reinforcement structure according to claim 7, characterized in that: The material of each of the first adhesion layer, the second adhesion layer and the third adhesion layer is selected from at least one of aluminum oxide and titanium; The thickness of each of the first adhesive layer, the second adhesive layer, and the third adhesive layer is 5-10 nm.

9. The method for manufacturing a MEMS gas sensor with a polymer reinforced structure according to claim 1, wherein: In step (6), the working area is first covered with a photoresist to protect it, and the first dielectric layer and the second dielectric layer of the protective area outside the working area that is not covered by the photoresist are removed by dry etching to form a release window. The release window is further used to etch away the second dielectric layer and a portion of the thickness of the substrate below the working area, so that the working area is released to form a suspended structure.

10. A MEMS gas sensor with a polymer reinforced structure manufactured by the manufacturing method according to any one of claims 1 to 9.

Images