A micro-electro-mechanical system based sapphire substrate gas sensor and a manufacturing method thereof

Abstract

The present application relates to a kind of micro-electro-mechanical system-based sapphire-based gas sensor and its manufacturing method, wherein the gas sensor includes the following parts in stacked arrangement: substrate with heat insulation cavity; Support layer is arranged on substrate, and has heat accumulation area suspended above heat insulation cavity; Heating assembly is arranged on support layer, with heating wire; Dielectric layer is arranged on heating assembly, and has heat accumulation area suspended above heat insulation cavity; Detection electrode is arranged on dielectric layer; Sensing layer is arranged on detection electrode, and gas-sensitive material is deposited;Wherein, the heat accumulation area of at least one of support layer and dielectric layer has several through holes along the stacking direction, and the aperture of through hole in the layer of support layer and dielectric layer is gradually changed in the way of extending direction from heat accumulation area to periphery.

Description

Technical Field

[0001] This invention relates to the field of gas sensor technology, and in particular to a sapphire-based gas sensor based on microelectromechanical systems and its manufacturing method. Background Technology

[0002] Metal-oxide-semiconductor (MOS) gas sensors are used to sense gases from an object by measuring the change in conductivity that occurs when a MOS reacts with a gas. These MOS gas sensors are widely used due to their low manufacturing cost, small size, high high-temperature stability, high sensitivity, and fast response speed.

[0003] Especially when using metal oxide semiconductors with nanostructures, the inherent large specific surface area of ​​the nanostructures can maximize the reaction between the metal oxide semiconductor and the gas, and the gas can diffuse rapidly into the characteristic pores of the metal oxide semiconductor with large nanostructures, thereby further enhancing the above advantages of metal oxide semiconductor gas sensors.

[0004] CN108318548A discloses a single-cantilever gas sensor, comprising a silicon substrate, a support film, a heating resistor, an isolation film, and a detection electrode stacked sequentially. The gas sensor is T-shaped, having a substrate structure and a cantilever structure, with a gas-sensitive material disposed at the end of the cantilever structure. This invention also provides a sensor array composed of single-cantilever gas sensors and a method for fabricating the gas sensor, comprising: (1) selecting a silicon substrate; (2) fabricating a support film; (3) fabricating a heating resistor; (4) fabricating an isolation film; (5) fabricating a detection electrode; (6) releasing the film; and (7) loading the gas-sensitive material.

[0005] CN102359981A discloses a resistive gas sensor with a six-layer structure supported by two cantilever beams and its fabrication method. The sensor structure includes: a substrate frame, a heat insulation cavity, a heating film region, a transition region, support cantilever beams, heating resistance wires, power supply leads, power supply electrodes, an isolation layer, interdigitated electrodes, detection leads, detection electrodes, and a sensitive membrane. Its structural features are as follows: the heating film region located above the heat insulation cavity is connected to the substrate frame through the transition region and support cantilever beams; the heating resistance wires are arranged in a zigzag pattern on the heating film region and are connected to the power supply electrodes on the substrate frame through power supply leads; the isolation layer covers the heating film region and support cantilever beams, and tightly wraps the heating resistance wires and power supply leads; the interdigitated electrodes are arranged on the isolation layer and are connected to the detection electrodes through detection leads; the sensitive membrane is located on the isolation layer on the heating film region, covering the entire interdigitated electrode and having good electrical connection with it.

[0006] Traditional semiconductor resistive gas sensors utilize semiconductor processes such as sputtering and evaporation to directly fabricate gas-sensitive materials on a micro-thermal platform. However, the dense surface structure significantly reduces the response and sensitivity of the gas-sensitive material, and the ceramic substrate greatly increases device power consumption. To maintain low power consumption, existing MEMS semiconductor gas sensors typically employ a heat-insulating cavity formed by etched cutouts in the substrate. These cutouts reduce mechanical strength to some extent. When the sensor is subjected to unexpected sudden impacts or vibrations, this reduced mechanical strength can lead to uncertainties in the sensor's mechanical stability and operating status. Current technologies often address this by increasing the width of the cantilever beam or reducing or eliminating it to ensure mechanical stability, but this results in a significant increase in heat dissipation. Conversely, reducing power consumption involves increasing the number of cantilever beams or decreasing their width, which sacrifices some mechanical strength. Therefore, the technology still faces at least one or more unresolved technical problems.

[0007] Furthermore, on the one hand, there are differences in understanding among those skilled in the art; on the other hand, the applicant studied a large number of documents and patents when making this invention, but due to space limitations, not all details and contents were listed in detail. However, this does not mean that the present invention does not possess the features of these prior art. On the contrary, the present invention already possesses all the features of the prior art, and the applicant reserves the right to add relevant prior art to the background art. Summary of the Invention

[0008] In view of the shortcomings of the prior art, the present invention provides a sapphire-based gas sensor based on microelectromechanical systems and a method for manufacturing the same, aiming to solve at least one or more technical problems existing in the prior art.

[0009] To achieve the above objectives, the present invention provides a sapphire-based gas sensor based on a microelectromechanical system (MEMS), comprising the following stacked components:

[0010] The base has a heat-insulating cavity;

[0011] A support layer, disposed on the substrate, has a heat-concentrating zone suspended above the insulation cavity;

[0012] A heating element, disposed on a support layer, has a heating wire;

[0013] A dielectric layer is disposed on the heating assembly and has a heat-concentrating area suspended above the insulation cavity;

[0014] The detection electrode is disposed on the dielectric layer;

[0015] The sensing layer, disposed on the detection electrode, has gas-sensitive material deposited on it;

[0016] in,

[0017] At least one of the support layer and dielectric layer has a heat-gathering region with a plurality of through-holes extending along the stacking direction, and the aperture of the through-holes in each of the support layer and dielectric layer is configured to gradually change from the heat-gathering region to the peripheral side. In this invention, when the support layer and dielectric layer, especially the heat-gathering region in the middle of the support layer and dielectric layer, have a plurality of through-holes, the air-accommodating cavity is increased by means of the through-holes, that is, the effective contact area or effective heat transfer area between heat and air is increased. Since the thermal conductivity of air is much lower than that of the substrate, the through-holes increase the heat conduction between heat and air. Furthermore, since the heat loss through heat conduction with air is lower than the heat loss through heat conduction with the substrate when heat is conducted through both the air medium and the substrate medium, higher heating efficiency can ultimately be obtained.

[0018] Preferably, the heat-concentrating zone of the support layer and / or dielectric layer is composed of multiple cantilever beams and a load-bearing layer, wherein one end of each of the multiple cantilever beams is connected to the load-bearing layer, and the other end of each of the multiple cantilever beams is connected to the support layer and / or dielectric layer, wherein,

[0019] The through-holes in the heat-gathering zone are arranged in a manner that gradually decreases in size from the support layer along the direction of the cantilever beam. In this invention, when the aperture of the through-holes in the heat-gathering zone of at least one of the support layer and / or dielectric layer is arranged in a manner that gradually decreases outward from the support layer along the direction of the cantilever beam, since the aperture of the support layer is larger, when heat is conducted longitudinally to the heat-gathering zone, especially into the large aperture region of the middle support layer, the effective heat transfer area between heat and air is larger than the effective heat transfer area between heat and air when heat enters the small aperture of the cantilever beam on the outer side of the support layer. Therefore, within the same layer structure, the heat loss generated along the cantilever beam towards the support layer gradually decreases, thereby improving the heat retention efficiency of the support layer. Compared to the portion farther from the support layer and the relatively small through-holes on the cantilever beam, the mechanical strength of the cantilever beam or the connection between the cantilever beam and the substrate can be guaranteed. Thus, while improving the thermal power consumption performance of the sensor, a certain level of mechanical strength can be guaranteed.

[0020] Preferably, the through holes in the heat-gathering zone are arranged in such a way that they gradually decrease from the bearing layer along the extension direction of the cantilever beam, while the cantilever beam is arranged in such a way that its lateral width gradually increases toward the end where the bearing layer is located.

[0021] Preferably, the heating assembly further includes heating electrodes, which are electrically connected to both ends of the heating wire, wherein...

[0022] The heating wire is configured to overlap with the carrier layer of the support layer and / or dielectric layer when viewed in the stacking direction.

[0023] Preferably, the heat-gathering regions of the support layer and the dielectric layer are configured to overlap or contain each other when viewed in the stacking direction.

[0024] Preferably, the detection electrode includes interdigitated electrodes, wherein the electrical interdigitations of a pair of interdigitated electrodes intersect each other to form a sensing region for detection, and the sensing region is configured to overlap with the carrier layer of the support layer and / or dielectric layer when viewed in the stacking direction.

[0025] Preferably, the sensing layer with deposited gas-sensitive material includes a first functional region and a second functional region, wherein,

[0026] The first functional area is configured to overlap / enclose the heat-generating area of ​​the support layer and / or dielectric layer when viewed in the stacking direction; and

[0027] The second functional area is integrally connected to the first functional area in such a way that it does not overlap with or contain the heat-generating areas of the support layer and / or dielectric layer when viewed in the stacking direction.

[0028] Preferably, the dielectric layer is configured with a receiving region whose shape is adapted to accommodate the heating electrode of the heating assembly.

[0029] Preferably, the support layer and / or dielectric layer is a composite film structure formed from at least one of silicon nitride and silicon oxide.

[0030] Preferably, the present invention provides a method for manufacturing a sapphire-based gas sensor based on microelectromechanical systems, comprising:

[0031] Configure the base;

[0032] Deposit the support layer onto the substrate;

[0033] Deposit a heating assembly containing heating wires into a support layer;

[0034] Deposit a dielectric layer onto the heating assembly;

[0035] Deposit the detection electrode onto the dielectric layer;

[0036] A sensing layer containing gas-sensitive material is deposited onto the detection electrode;

[0037] The structure formed by stacking the above-mentioned layers is etched to give the support layer and dielectric layer a heat-concentrating zone containing a cantilever structure.

[0038] in,

[0039] At least one of the support layer and the dielectric layer has a heat-gathering region having a plurality of through holes extending along the stacking direction, and the aperture of the through holes in each of the support layer and the dielectric layer is configured in such a manner that it gradually changes from the heat-gathering region to the peripheral side. Attached Figure Description

[0040] Figure 1 This is a three-dimensional structural assembly diagram of a sapphire-based gas sensor based on a microelectromechanical system according to a preferred embodiment of the present invention.

[0041] Figure 2 This is an isometric structural diagram of a sapphire-based gas sensor based on a microelectromechanical system according to a preferred embodiment of the present invention.

[0042] Figure 3 This is a top view schematic diagram of a sapphire-based gas sensor based on a microelectromechanical system according to a preferred embodiment of the present invention.

[0043] Figure 4 This is a schematic diagram of the structure of a heating assembly according to a preferred embodiment of the present invention;

[0044] Figure 5 This is a schematic diagram of the detection electrode according to a preferred embodiment of the present invention;

[0045] Figure 6 This is a partial enlarged schematic diagram of the sensing layer according to a preferred embodiment of the present invention.

[0046] List of reference numerals

[0047] 10: Substrate; 20: Support layer; 30: Heating component; 40: Dielectric layer; 50: Detection electrode; 60: Sensing layer; 70: Gas-sensitive material; 301: Heating electrode; 302: Heating wire; 501: Interdigitated electrode; 502: Electrical interdigitated electrode; 503: Sensing area. Detailed Implementation

[0048] The following is a detailed explanation with reference to the accompanying drawings.

[0049] This invention provides a sapphire-based gas sensor based on microelectromechanical systems, such as... Figure 1 As shown, it may include the following parts arranged in a vertically stacked manner:

[0050] Substrate 10 serves as a substrate structure for supporting or depositing other layer components;

[0051] The support layer 20, which is deposited on the surface of the substrate 10, is composed of a multilayer composite film of silicon nitride / silicon dioxide;

[0052] Heating component 30, which is deposited on the surface of support layer 20, is used to provide a temperature environment for gas-sensitive reactions;

[0053] The detection electrode 50 is deposited above the heating component 30 and partially overlaps the heating component 30 vertically;

[0054] A dielectric layer 40 is deposited between the heating component 30 and the detection electrode 50 to maintain electrical isolation between the two.

[0055] The sensing layer 60, which is deposited on the surface of the dielectric layer 40 and partially overlaps vertically with the detection electrode 50, contains a gas-sensitive material 70 for gas-sensitive reactions.

[0056] According to a preferred embodiment, the substrate 10 may be made of sapphire. Further, the substrate 10 may also be made of at least one of silicon, gallium nitride, and silicon carbide.

[0057] According to a preferred embodiment, such as Figure 1 As shown, a vertically penetrating groove structure is constructed at the center of the base 10. This groove structure can serve as a gas containment cavity and an insulation cavity, reducing heat transfer and loss of the heating assembly 30 above the base 10 within the base 10. In particular, to adapt to the cantilever structure, the groove structure can be constructed as a triangular structure.

[0058] According to a preferred embodiment of the present invention, the substrate 10 can be, for example, a cubic substrate with a side length of 800 μm and a thickness of approximately 400 μm. The side length of the triangular through-hole structure at the center of the substrate 10 can be 240 μm.

[0059] According to a preferred embodiment, such as Figure 1 As shown, the support layer 20 is deposited on the top surface of the substrate 10. It can be formed by a multilayer composite film structure composed of silicon nitride and silicon oxide. Since the silicon oxide film has compressive stress and the silicon nitride film has tensile stress, a single type of film structure is difficult to meet the requirements of practical applications. Preferably, the support layer 20 can be formed, for example, by stacking silicon oxide films on both sides and a silicon nitride film in between. Since the thermal conductivity of the multilayer composite film structure composed of silicon nitride and silicon oxide is much lower than that of the substrate structure made of silicon, gallium nitride, silicon carbide, etc., heat can be well retained on the support layer 20, thereby greatly improving the heating efficiency.

[0060] According to a preferred embodiment, such as Figure 1 As shown, the central region of the support layer 20 has a heat-concentrating zone, which is approximately triangular in shape, similar to the through-groove region of the base 10, and a cantilever structure is constructed within the heat-concentrating zone. Preferably, in this invention, the cantilever structure can be a three-cantilever structure. In particular, depending on assembly requirements, a two-cantilever or four-cantilever structure can also be constructed.

[0061] According to a preferred embodiment, such as Figure 1 As shown, the heat-gathering area at least partially overlaps with the through-groove area of ​​the substrate 10 in the vertical direction, and preferably, the heat-gathering area is contained within the through-groove area of ​​the substrate 10.

[0062] According to a preferred embodiment, such as Figure 1As shown, one end of each of the three cantilever beams in the heat-gathering zone extends laterally outward along the support layer 20 in three different directions, and one end of each of the three cantilever beams is connected to the remaining substrate layer of the support layer 20. In particular, the three directions correspond to the three vertices of the triangular region.

[0063] According to a preferred embodiment, the cantilever structure can be obtained by etching the support layer 20.

[0064] Furthermore, the other ends of the three cantilever beams extending inward along the support layer 20 converge and connect to the carrier layer (active area). This carrier layer can be used to deposit and support part of the structure of the heating component 30, and the heat provided by the heating component 30 can be transferred to the carrier layer. The carrier layer, together with the cantilever beam structure connected to it, distributes the heat provided by the heating component 30 in the heat-gathering zone formed by the two. Since the cantilever beam structure and the carrier layer have a small heat transfer coefficient and heat transfer rate along the surface of the support layer 20 due to their structure and material properties, more heat is concentrated in the heat-gathering zone formed by the three cantilever beam structures in the middle of the support layer 20 to ensure the temperature environment required for gas detection, thereby improving detection sensitivity and response speed.

[0065] According to a preferred embodiment, such as Figure 1 As shown, the supporting layer overlaps vertically and is contained within the through-groove area of ​​the base 10, and the supporting layer can be a triangular area with the center of the heat-gathering zone as the base point and reduced in proportion or multiple of that base point.

[0066] According to a preferred embodiment, the support layer 20 can be, for example, a cubic substrate with a side length of 800 μm and a thickness of approximately 2 μm. Further, for the triangular heat-gathering region at the center of the support layer 20, the entire triangular heat-gathering region can be an equilateral triangle with a side length of 240 μm.

[0067] Furthermore, the width of the cantilever beam can be 15μm, its length can be 70μm, and the load-bearing layer (active area) connected by the three cantilever beams can be an equilateral triangle with a side length of 100μm.

[0068] According to a preferred embodiment, in order to meet the power consumption and component assembly strength requirements of semiconductor gas sensors, when it is necessary to reduce the overall power consumption of the sensor device, for example, the lateral width of the cantilever beam can be reduced accordingly, and when it is necessary to increase the mechanical strength of the layer structure, the lateral width of the cantilever beam can be increased accordingly.

[0069] According to a preferred embodiment, such as Figure 1 As shown, a heating component 30 is deposited on the top surface of the support layer 20.

[0070] Furthermore, such as Figure 1 and Figure 4As shown, the heating assembly 30 consists of a pair of heating electrodes 301 with the same configuration and a heating wire 302 connected to the heating electrodes 301.

[0071] According to a preferred embodiment, such as Figure 4 As shown, the heating electrode 301 is a rectangular electrode. The heating wire 302 is meandering. Further, portions of the pair of heating electrodes 301 on the same side extend to the same side and are electrically connected to both ends of the heating wire 302 via leads. Preferably, the working area or heating area of ​​the heating assembly 30 is the area covered by the heating wire 302.

[0072] According to a preferred embodiment, the heating wire 302 is a meandering heating wire, and the heat output of the entire heating assembly 30 is mainly concentrated at the heating wire 302 in the middle of the structure, thus achieving localized heating effect in a small area.

[0073] According to a preferred embodiment, the heating electrode 301 can be a square electrode with a side length of 200 μm, and the heating wire 302 can have a line width of 5 μm and a line spacing of 5 μm.

[0074] According to a preferred embodiment, such as Figure 1 As shown, when the heating assembly 30 is deposited on the top surface of the support layer 20, the heating wire 302 is deposited on the bearing layer in the middle of the support layer 20, which is connected by three cantilever beams. The lead wire between the heating wire 302 and the heating electrode 301 can be deposited on the cantilever structure, and the pair of heating electrodes 301 of the heating assembly 30 are symmetrically distributed on both sides of the heating wire 302 about the center of the support layer 20.

[0075] In particular, the heat-concentrating zone in the middle of the support layer 20 can serve as a carrier for the heating wire 302, and when the heating wire 302 is working, the heat-concentrating zone in the middle of the support layer 20, constructed by the cantilever structure and the bearing layer, can concentrate more of the heat generated by the heating wire 302 in the heat-concentrating zone of the support layer 20.

[0076] According to a preferred embodiment, such as Figure 1 As shown, after the heating component 30 is deposited on the surface of the support layer 20, a dielectric layer 40 is deposited on the surface of the heating component 30. Specifically, the dielectric layer 40 can be a single-layer film structure made of silicon oxide, or it can be a multilayer composite film structure composed of silicon nitride / silicon dioxide, the same as the support layer 20.

[0077] According to a preferred embodiment, such as Figure 1 As shown, the dielectric layer 40 has a layer structure similar to or the same as that of the support layer 20, that is, the center of the dielectric layer 40 is constructed with a heat-gathering zone composed of a cantilever structure, and preferably a three-cantilever structure.

[0078] Furthermore, the dielectric layer 40 is configured with a receiving area that is adapted to the shape of the heating electrode 301 of the heating assembly 30 in a portion of the region corresponding to the heating electrode 301 of the heating assembly 30. When the dielectric layer 40 is deposited onto the top surface of the heating assembly 30 and / or the support layer 2, the heating electrode 301 can be fitted into the receiving area to protrude from the dielectric layer 40 so as to establish an electrical connection with external electrical components. The heating wire 302 of the heating assembly 30 is sandwiched between the support layer 20 and the dielectric layer 40, and is specifically located on the heat-gathering area formed by the cantilever structure between the support layer 20 and the dielectric layer 40.

[0079] According to a preferred embodiment, the dielectric layer 40 can be, for example, a square substrate with a side length of 800 μm and a thickness of about 300 nm, and except for the thickness, the other dimensions of the triangular heat-gathering region in the middle of the dielectric layer 40 are the same as the corresponding region of the support layer 20 below it.

[0080] According to a preferred embodiment, such as Figure 1 As shown, after depositing a dielectric layer 40 on the top surface of the heating assembly 30, a detection electrode 50 is deposited on the surface of the dielectric layer 40. Specifically, as... Figure 1 and Figure 5 As shown, the detection electrode 50 is formed by connecting or combining a pair of interdigitated electrodes 501 with the same configuration.

[0081] Specifically, such as Figure 5 As shown, the interdigital electrode 501 is a roughly rectangular planar interdigital electrode. Further, each of the two interdigital electrodes 501 forms an electrical interdigital finger 502 at one of its opposite ends, and the electrical interdigital fingers 502 at the ends of the two interdigital electrodes 501 intersect each other to form a sensing region 503 (interdigital region).

[0082] According to a preferred embodiment, such as Figure 1 As shown, a pair of interdigital electrodes 501 of the detection electrode 50 are deposited on the two end surfaces symmetrical about the dielectric layer 40, while the sensing region 503 formed by the intersection of the two interdigital electrodes 501 is deposited on the carrier layer in the middle of the dielectric layer 40, and the part between the sensing region 503 and the interdigital electrodes 501 is deposited on the cantilever structure.

[0083] According to a preferred embodiment, the sensing region 503 is a triangular region adapted to the shape of its bottom dielectric layer 40 and the middle carrier layer of the support layer 20.

[0084] According to a preferred embodiment, the interdigitated electrode 501 of the detection electrode 50 can be a square electrode with a side length of 200 μm, and the line width and line spacing of the detection electrode 50 can be 5 μm.

[0085] According to a preferred embodiment, the dielectric layer 40, while maintaining heat conduction, also serves to maintain electrical isolation between the detection electrode 50 and the heating component 30.

[0086] According to a preferred embodiment, such as Figure 1 As shown, after depositing the detection electrode 50 on the top surface of the dielectric layer 40, the sensing layer 60 is deposited on the top surface of the dielectric layer 40 and the detection electrode 50.

[0087] According to a preferred embodiment, such as Figure 1 As shown, the sensing layer 60 can be composed of a first functional region and a second functional region deposited on the surface of the dielectric layer 40 and connected together.

[0088] Specifically, such as Figure 1 As shown, the first functional area of ​​the sensing layer 60 is adapted to the shape of the sensing area 503 of the detection electrode 50, and the first functional area is deposited on the surface of the sensing area 503 of the detection electrode 50; the second functional area of ​​the sensing layer 60 is approximately pentagonal in shape, and the second functional area is deposited on the other side of the heating electrode 301 of the heating assembly 30 symmetrical about the sensing area 503.

[0089] Preferably, the first functional area can serve as the main functional area for the gas-sensitive reaction, and the second functional area can serve as a compensation area for the main functional area. That is, it does not directly participate in the gas-sensitive reaction, but at least has the function of maintaining the mechanical stability of the first functional area, for example, through integral molding in the same layer.

[0090] According to a preferred embodiment of the present invention, the sensing layer 60 can be a porous alumina (AAO) substrate structure on which a gas-sensitive material 70 is deposited. Preferably, the gas-sensitive material 70 may include at least one of SnO2, ZnO, In2O3, NiO, or other metal oxides.

[0091] According to a preferred embodiment, the porous alumina (AAO) substrate can be a dual-pore type substrate, which is composed of multiple dual-pore nanotubes, each having two interconnected openings. Specifically, the single-pore type alumina (AAO) substrate structure is composed of multiple single-pore nanotubes, where one opening at each end of the single-pore nanotube is closed, while the other opening is open.

[0092] According to a preferred embodiment, the process of depositing a porous alumina (AAO) substrate structure above the dielectric layer 40 and the detection electrode 50 is as follows: depositing an aluminum electrode onto the substrate by electron beam evaporation, and forming a porous alumina (AAO) substrate by two-step anodic oxidation.

[0093] Specifically, the general steps for preparing porous alumina (AAO) using the two-step anodizing method are as follows: aluminum is calcined under vacuum at high temperature, electrochemically polished in an acidic mixed aqueous solution such as sulfuric acid and phosphoric acid, the polished sample is anodized at room temperature and using a specific acidic aqueous solution (e.g., oxalic acid aqueous solution) as the electrolyte and a specific oxidation voltage is applied, thereafter the surface anodized layer is dissolved in an acidic mixed aqueous solution such as phosphoric acid and chromic acid, and the aluminum plate after the anodized layer is dissolved is subjected to a second anodizing under the same conditions as above.

[0094] According to a preferred embodiment, after the sensing layer 60 made of porous alumina (AAO) is deposited, a gas-sensitive material 70 needs to be deposited on the sensing layer 60, that is, a metal oxide is atomically deposited on the sensing layer 60. Specifically, as shown in FIG7, the gas-sensitive material 70 can be deposited on the wall of a double-pore nanotube on a porous alumina (AAO) substrate.

[0095] According to a preferred embodiment, after depositing the gas-sensitive material 70 containing metal oxides onto the sensing layer 60, a catalytic material needs to be deposited onto the sensing layer 60 so that the catalytic material and the gas-sensitive material 70 are directly or indirectly deposited in contact. When the gas-sensitive material 70 reacts with the gas to be detected (the adsorption and desorption of gas on the material surface will cause a significant change in the electrical properties of the material, such as resistivity), the catalytic material can promote the reaction between the gas to be detected and the gas-sensitive material 70.

[0096] According to a preferred embodiment, the catalytic material may include metals such as Pt and Pd.

[0097] According to a preferred embodiment, in this invention, the thickness of the porous alumina (AAO) substrate structure can be, for example, 500 nm. The pore size of the porous alumina (AAO) substrate structure can be 400 nm. Further, the first functional region of the sensing layer 60, which overlaps with the sensing region 503 of the detection electrode 50, can be an equilateral triangle structure with a side length of 100 μm, the same size as the silicon island in the middle of the support layer 20 and the dielectric layer 40.

[0098] In some alternative embodiments, when the sensing layer 60 is a porous alumina (AAO) substrate structure, and preferably a dual-hole type substrate, the detection electrode 50 deposited on the dielectric layer 40 may include two sets of detection electrodes 50 symmetrical about the sensing layer 60 in the vertical direction, that is, one set of detection electrodes 50 is deposited on a substrate such as... Figure 1 Below the sensing layer 60 shown, another set of detection electrodes 50 is deposited above the sensing layer 60 (not shown in the figure), thus the sensing layer 60 is sandwiched between the set of detection electrodes 50.

[0099] Furthermore, the sensing regions 503 contained in each of the two sets of detection electrodes 50 are vertically overlapped with the first functional region of the sensing layer 60, and the two ends of the multiple double-hole nanotubes constituting the sensing layer 60 abut against the sensing regions 503 on both sides respectively, and the sensing regions 503 on both sides are gas-connected by means of the interconnected openings.

[0100] According to a preferred embodiment, the current of the gas sensor is mainly distributed in the sensing layer 60, that is, the contact surface between the detection electrode 50 and the sensing layer 60. Some current also flows through the nanotube wall on which the gas-sensitive material 70 is deposited. In this invention, the contact surface between the detection electrode 50 and the sensing layer 60 is the overlapping area of ​​the sensing region 503 of the detection electrode 50 and the first functional region of the sensing layer 60. In other words, most of the gas-sensitive reaction occurs in the sensing region 503 of the detection electrode 50, and a small part is inside the nanotube wall.

[0101] According to a preferred embodiment, after all the above-mentioned layer structures and functional component structures have been deposited, an etching process is then used to obtain the desired result. Figures 1-3 The cantilever structure shown is used to ultimately form the sapphire-based semiconductor gas sensor structure described in this embodiment.

[0102] According to a preferred embodiment, in addition to the three-beam structure described in this embodiment, the central heat-gathering zone can also be constructed as a two-beam structure or a four-beam structure (not shown in the figure). In particular, if the beam structure is constructed as a four-beam structure, the stacking order of the layer structure and the structure of each functional component in this embodiment can remain unchanged, but it is necessary to adaptively adjust, for example, the molding structure of the heating component 30, the detection electrode 50, and the sensing layer 60, and their arrangement when deposited in each functional layer.

[0103] According to a preferred embodiment, the sensing layer 60 of the present invention adopts a porous alumina (AAO) substrate, whose heat transfer coefficient in the lateral direction is relatively smaller than that in the vertical direction. Therefore, the lateral heat loss is small, and the vertical heat transfer efficiency can be maintained relatively high to maintain the temperature environment of the gas-sensitive reaction, thereby improving the response rate and accuracy of gas detection.

[0104] According to a preferred embodiment, generally, microelectromechanical systems (MEMS) based semiconductor gas sensors can be portablely installed or applied in various terminals. To maintain low power consumption, the bottom substrate of a MEMS-type semiconductor gas sensor (e.g., the sapphire substrate 10 of this invention) typically has a heat-insulating cavity formed by etched cutouts. However, the cutouts on the bottom substrate reduce the overall mechanical strength. When the sensor device is subjected to unexpected sudden impacts or vibrations, the decrease in mechanical strength can lead to uncertainties in the overall mechanical stability and operational stability of the sensor device or terminal device. In the prior art, to solve this problem, the width of the cantilever beam is usually increased, or the cantilever beam is reduced or even eliminated to ensure mechanical stability. However, this results in a significant increase in heat consumption. On the other hand, to reduce device power consumption, the number of cantilever beams is increased, or the width of the cantilever beams is reduced. This measure faces the challenge of sacrificing some mechanical strength. Therefore, a MEMS-type semiconductor gas sensor that balances mechanical strength and power consumption is needed.

[0105] According to a preferred embodiment of the present invention, when depositing or etching the support layer 20 and / or the dielectric layer 40, a plurality of vias (not shown in the figure) extending along the stacking direction can be etched or constructed on at least one of the layers, and the vias are preferably opened on the heat-gathering area containing the cantilever structure in the middle of the support layer 20 and / or the dielectric layer 40, and the form of the vias can be similar to that of the sensing layer 60 on which the gas-sensitive material 70 is deposited.

[0106] According to a preferred embodiment, in this invention, it is preferable to construct a plurality of through holes in the heat-gathering area containing the cantilever structure in the middle of the support layer 20 and the dielectric layer 40. It is well known that the power consumption of the micro-thermal platform composed of the substrate 10, support layer 20, heating component 30, dielectric layer 40, and detection electrode 50 is the main source of power consumption for MEMS-type semiconductor gas sensors. The heat loss of the sensor includes three forms: heat conduction, heat convection, and heat radiation, with heat conduction and heat convection being the primary forms, and heat radiation accounting for a relatively small proportion.

[0107] Furthermore, in MEMS-type semiconductor gas sensors, heat conduction mainly includes two types: heat conduction with air and heat conduction from the active region (supporting layer) along the cantilever to the substrate (substrate 10). Among them, the thermal conductivity of air is much lower than that of the substrate (substrate 10). Therefore, the heat lost through heat conduction mainly occurs in the substrate (substrate 10).

[0108] Preferably, in this invention, a plurality of through holes are constructed in the heat-gathering region of at least one of the support layer 20 and the dielectric layer 40. These through holes reduce the effective conduction area for heat diffusion within the heat-gathering region and other layer structures, and increase the air-accommodating cavity by means of the through holes, that is, increase the effective contact area or effective conduction area between heat and air. Since the thermal conductivity of air is much lower than that of the substrate (substrate 10), the presence of a plurality of through holes in the heat-gathering region of at least one of the support layer 20 and the dielectric layer 40 increases the thermal conduction between heat and air. Furthermore, since the heat loss through conduction with air is lower than the heat loss through conduction with the substrate (substrate 10) when heat is conducted through both the air medium and the substrate medium, higher heating efficiency can ultimately be obtained.

[0109] Furthermore, when the heat-gathering zone of at least one of the support layer 20 and the dielectric layer 40 is configured in the form of a plurality of through holes, the width of the cantilever beams in the support layer 20 and the dielectric layer 40 can be appropriately increased to compensate for the decrease in the mechanical strength of the layer structure and the overall sensor structure caused by the opening of through holes.

[0110] In particular, for MEMS semiconductor gas sensors with cantilever structures, due to their stacked structure and the differences in Young's modulus and coefficient of thermal expansion of the materials in each layer, the active region of the sensor, namely the central bearing layer described in the embodiments of the present invention, will experience significant thermal stress and deformation under certain high-temperature conditions. The significant thermal stress and deformation will affect the performance of the sensor, such as causing the cantilever to break, especially at the connection points or corners where the cantilever and the substrate are connected.

[0111] According to a preferred embodiment, when the winding method of the heating wire 302 of the heating assembly 30 is determined, the thermal stress generated by the bearing layer in the middle of the support layer 20 and / or dielectric layer 40, which is jointly connected by multiple cantilever structures, is greater than the thermal stress generated by the surrounding substrate. This is because the coefficient of thermal expansion of platinum metal used to make the heating wire 302 is much greater than that of silicon oxide and silicon nitride. In other words, the thermal stress in the area where the heating wire exists is much greater than that in other insulating areas. Furthermore, as the temperature increases, the generated thermal stress is greater, and the corresponding deformation or displacement amplitude is also greater, thereby the degree of deformation / displacement of the active area or the bearing layer is also greater.

[0112] According to a preferred embodiment, when heat is transversely conducted and distributed in the heat-gathering zone in the middle of the support layer 20 and the dielectric layer 40, it usually exhibits a relatively clear temperature gradient change pattern. Generally speaking, the temperature or heat will gradually decrease or drop from the support layer (active area) along the extension direction of the cantilever beam to the surrounding substrate. When the width of the cantilever beam is of equal width, the heat has a better uniform distribution in the heat-gathering zone, that is, the heat is mainly concentrated in the support layer (active area) and at least a portion of the cantilever beam on the side closer to the support layer (active area).

[0113] According to a preferred embodiment, based on the heat distribution pattern in the support layer 20 and / or dielectric layer 40, especially in the load-bearing layer (active region) and cantilever structure of the support layer 20 and / or dielectric layer 40, in this invention, when the heat-gathering zone of at least one of the support layer 20 and dielectric layer 40 is configured with a plurality of through holes, the aperture of the holes in the same layer structure is not completely or uniform, but gradually decreases from the load-bearing layer (active region) along the cantilever direction. That is, the through holes located in the load-bearing layer (active region) and closer to the center of the load-bearing layer (active region) have larger apertures. The larger the aperture of the via, the smaller the aperture of the via that is farther away from the support layer (active region) and closer to the connection end between the cantilever and the substrate. Since the heat generated by the heating wire 302 is mainly concentrated in the support layer connected to the cantilever, and the cantilever also has some heat, and in order to ensure or stabilize the effect of heat on the sensing layer 60, it is also preferable to concentrate more heat in the area where the gas-sensitive material 70 is deposited or in contact, i.e., on the support layer. Therefore, the heat conducted to the outer substrate through the cantilever should be reduced. Thus, the heat accumulation in at least one of the support layer 20 and / or dielectric layer 40 is limited. When the apertures of the through-holes in the zone are arranged in a manner that gradually decreases outward from the load-bearing layer (active zone) along the direction of the cantilever beam, the larger aperture in the middle load-bearing layer (active zone) results in a larger effective heat transfer area between heat and air when heat is conducted longitudinally to the heat-gathering zone, especially when entering the large-aperture area of ​​the middle load-bearing layer (active zone). This is compared to the effective heat transfer area with air when heat enters the small-aperture cantilever beam on the outer side of the load-bearing layer (active zone). Therefore, within the same layer structure, the heat loss along the cantilever beam towards the load-bearing layer (active zone) gradually decreases. This improves the heat retention efficiency of the carrier layer (active region). Compared to the portion far from the carrier layer (active region) and the relatively small through holes on the cantilever, the mechanical strength of the cantilever or the connection between the cantilever and the substrate can be guaranteed. In addition, to accommodate the enlargement of the aperture of the central carrier layer (active region), the width of the connection between the cantilever and the central carrier layer (active region) can be appropriately increased, and the cantilever can be constructed as a gradually widening structure, that is, the width of the cantilever gradually increases towards the carrier layer (active region) to compensate for the decrease in mechanical strength caused by the increase in aperture.

[0114] According to a preferred embodiment, the present invention relates to a fabrication process for the aforementioned sapphire-based gas sensor based on microelectromechanical systems, comprising:

[0115] A silicon dioxide / silicon nitride multilayer film is deposited on substrate 10 to serve as support layer 20;

[0116] Deposition heating assembly 30 to support layer 20;

[0117] A dielectric layer 40 is deposited to the support layer 20 to partially cover the heating assembly 30;

[0118] Deposit detection electrode 50 to dielectric layer 40;

[0119] An aluminum electrode is deposited onto a substrate by electron beam evaporation, followed by two-step anodizing to form the sensing layer 60.

[0120] Deposit gas-sensitive material 70 to sensing layer 60;

[0121] Deposit catalytic material onto the sensing layer 60;

[0122] The cantilever structure is obtained by etching the layer structure formed by stacking the above-mentioned layers.

[0123] It should be noted that the specific embodiments described above are exemplary. Those skilled in the art can devise various solutions inspired by the disclosure of this invention, and these solutions all fall within the scope of this invention and its protection. Those skilled in the art should understand that this specification and its accompanying drawings are illustrative and not intended to limit the scope of the claims. The scope of protection of this invention is defined by the claims and their equivalents. This specification contains multiple inventive concepts; terms such as "preferredly," "according to a preferred embodiment," or "optionally" indicate that the corresponding paragraph discloses an independent concept. The applicant reserves the right to file divisional applications based on each inventive concept.

Claims

1. A sapphire-based gas sensor based on microelectromechanical systems, characterized in that, include: The base (10) has a heat insulation cavity; A support layer (20) is disposed on the substrate (10) and has a heat-concentrating zone suspended above the insulation cavity; A heating assembly (30) is disposed on the support layer (20) and includes a heating wire (302). A dielectric layer (40) is disposed on the heating assembly (30) and has a heat-concentrating area suspended above the heat insulation cavity; A detection electrode (50) is disposed on the dielectric layer (40); A sensing layer (60) is disposed on the detection electrode (50) and a gas-sensitive material (70) is deposited thereon. in, At least one of the support layer (20) and dielectric layer (40) has a heat-gathering region having a plurality of through holes formed along the stacking direction, and the aperture of the through holes in each of the support layer (20) and dielectric layer (40) is configured in such a way that it gradually changes from the heat-gathering region to the peripheral side.

2. The gas sensor according to claim 1, characterized in that, The heat-concentrating zone of the support layer (20) and / or dielectric layer (40) is composed of multiple cantilever beams and a load-bearing layer, wherein one end of each of the multiple cantilever beams is connected to the load-bearing layer and the other end of each of the multiple cantilever beams is connected to the support layer (20) and / or dielectric layer (40), wherein, The through holes in the heat-collecting zone are arranged in a manner that gradually decreases in size from the bearing layer along the extension direction of the cantilever beam.

3. The gas sensor according to claim 2, characterized in that, With the through holes in the heat-gathering zone arranged in a manner that gradually decreases from the bearing layer along the extension direction of the cantilever beam, the cantilever beam is arranged in a manner that gradually increases in width toward the end where the bearing layer is located.

4. The gas sensor according to claim 2 or 3, characterized in that, The heating assembly (30) further includes a heating electrode (301), and the heating electrode (301) is electrically connected to both ends of the heating wire (302), wherein, The heating wire (302) is configured to overlap with the carrier layer of the support layer (20) and / or dielectric layer (40) when viewed in the stacking direction.

5. The gas sensor according to claim 1, characterized in that, The heat-gathering regions of the support layer (20) and the dielectric layer (40) are configured to overlap or contain each other when viewed in the stacking direction.

6. The gas sensor according to claim 2, characterized in that, The detection electrode (50) includes interdigitated electrodes (501), each of the interdigitated electrodes (501) having electrical interdigitates (502) intersecting each other to form a sensing region (503) for detection, and the sensing region (503) is configured to overlap with the carrier layer of the support layer (20) and / or the dielectric layer (40) when viewed in the stacking direction.

7. The gas sensor according to claim 1, characterized in that, The sensing layer (60) with the deposited gas-sensitive material (70) includes a first functional region and a second functional region, wherein, The first functional area is configured to overlap / encompass the heat-gathering area of ​​the support layer (20) and / or dielectric layer (40) when viewed in the stacking direction; The second functional area is connected to the first functional area in such a way that it does not overlap with or contain the heat-gathering area of ​​the support layer (20) and / or dielectric layer (40) when viewed in the stacking direction.

8. The gas sensor according to claim 4, characterized in that, The dielectric layer (40) is configured with a receiving area for the heating electrode (301) of the heating assembly (30) in a shape adapted to the shape of the heating electrode (301).

9. The gas sensor according to claim 1, characterized in that, The support layer (20) and / or dielectric layer (40) are composite structures formed from at least one of silicon nitride and silicon oxide.

10. A method for manufacturing a sapphire-based gas sensor based on microelectromechanical systems, characterized in that, include: Configure the base (10); Deposit a support layer (20) onto the substrate (10); A heating assembly (30) containing a heating wire (302) is deposited onto the support layer (20). Deposit a dielectric layer (40) onto the heating assembly (30); Deposit detection electrode (50) onto the dielectric layer (40); A sensing layer (60) containing a gas-sensitive material (70) is deposited onto the detection electrode (50). The structure formed by stacking the above-mentioned layers is etched to form a heat-gathering zone containing a cantilever structure in the support layer (20) and the dielectric layer (40); in, At least one of the support layer (20) and dielectric layer (40) has a heat-gathering region having a plurality of through holes extending along the stacking direction, and the aperture of the through holes in each of the support layer (20) and dielectric layer (40) is configured in such a way that it gradually changes from the heat-gathering region to the peripheral side.

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