MEMS infrared thermopile sensor and preparation method thereof

Abstract

The invention relates to an MEMS infrared thermopile sensor and a preparation method thereof, the MEMS infrared thermopile sensor prepared by the preparation method of the MEMS infrared thermopile sensor comprises a substrate, the substrate comprises a first surface and a second surface which are opposite to each other, and the substrate is internally provided with a cavity formed on the second surface; a support layer; the thermopile device layer is positioned on the top surface of the supporting layer; a passivation layer; and the silicon dioxide aerogel is located in the cavity, and the heat conductivity coefficient of the silicon dioxide aerogel is lower than that of air. On the basis of low cost and good compatibility with the existing process, the response rate of the infrared device is improved.

Description

Technical Field

[0001] This invention relates to the field of semiconductor technology, specifically to a MEMS infrared thermopile sensor and its fabrication method. Background Technology

[0002] The core principle of MEMS infrared thermopile devices is based on the Seebeck effect, which states that a potential difference is generated when there is a temperature difference between the two ends of a closed circuit composed of two different conductors. With the development of MEMS technology, this effect has been revitalized at the microscale: multiple miniature thermocouple units are constructed on a silicon substrate using MEMS processes and connected in series to form a thermopile structure. The series connection of thermocouples allows the electrical signals generated by individual thermocouples to be superimposed, thus amplifying the signal. Thermopile devices can convert infrared radiation into electrical signals, enabling temperature detection or thermal imaging. Compared with traditional infrared sensors, its advantages include non-contact temperature measurement, low power consumption, room temperature operation, and no need for additional bias circuitry, resulting in outstanding cost-effectiveness.

[0003] Currently, when packaging MEMS infrared thermopile devices, the chip is usually fixed on the substrate under normal pressure. However, due to the limitation of the thermal conductivity of the air in the cavity, heat is lost at the hot end, resulting in low device response rate and thus affecting detection accuracy. Summary of the Invention

[0004] The technical problem solved by this invention is to provide a MEMS infrared thermopile sensor and its fabrication method, which improves the temperature difference between the hot and cold ends, thereby improving the responsivity and performance of the infrared device.

[0005] To address the aforementioned technical problems, the present invention provides a MEMS infrared thermopile sensor, comprising: a substrate, the substrate having opposing first and second surfaces, and a cavity formed on the second surface within the substrate; a support layer located on the first surface, the cavity penetrating the substrate and exposing the bottom surface of the support layer; a thermopile device layer located on the top surface of the support layer; a passivation layer located on the top surface of the thermopile device layer; and a silica aerogel located within the cavity, the silica aerogel having a thermal conductivity lower than that of air.

[0006] Optionally, the thermopile device layer includes: a first thermocouple layer located on the top surface of the support layer, the first thermocouple layer serving as the hot end of the thermopile; an insulating layer located on the top surface of the first thermocouple layer; and a second thermocouple layer including a first thermoelectric structure and a second thermoelectric structure, the first thermoelectric structure penetrating the insulating layer and contacting the first thermocouple layer, the second thermoelectric structure located on the surface of the first thermoelectric structure and on the surface of the insulating layer adjacent to the first thermocouple layer, the passivation layer exposing a portion of the surface of the second thermoelectric structure, the orthographic projection of the second thermoelectric structure on the exposed surface and its corresponding first thermoelectric structure on the substrate not overlapping the orthographic projection of the cavity on the substrate, and the second thermoelectric structure on the exposed surface and its corresponding first thermoelectric structure serving as the cold end of the thermopile.

[0007] Optionally, the first thermocouple layer is made of polycrystalline silicon, the insulating layer is made of silicon dioxide, and the second thermocouple layer is made of gold.

[0008] Optionally, the silica aerogel contains a light-blocking agent, which is one or more of zirconium oxide, titanium oxide, silicon carbide, and potassium titanate, and the particle size of the light-blocking agent is 20 nm to 500 nm.

[0009] Optionally, the MEMS infrared thermopile sensor further includes: a packaging substrate, the packaging substrate being located on the second side of the substrate.

[0010] Accordingly, the technical solution of the present invention also provides a method for fabricating a MEMS infrared thermopile sensor, comprising: providing a substrate, the substrate comprising a first side and a second side opposite to each other; depositing a support layer on the first side of the substrate; forming a thermopile device layer on the top surface of the support layer; forming a passivation layer on the top surface of the thermopile device layer; etching the substrate from the second side of the substrate until the bottom surface of the support layer is exposed to form a cavity; and forming a silica aerogel in the cavity.

[0011] Optionally, the method of forming the thermopile device layer on the top surface of the support layer includes: forming a patterned first thermocouple layer on a portion of the top surface of the support layer; forming an insulating layer on the top surface of the first thermocouple layer and the exposed support layer; etching the insulating layer to form a groove, the bottom surface of the groove exposing the top surface of the first thermocouple layer; forming a second thermocouple layer in the groove and on a portion of the top surface of the insulating layer, the second thermocouple layer including a first thermoelectric structure and a second thermoelectric structure, the first thermoelectric structure penetrating the insulating layer and contacting the first thermocouple layer, the second thermoelectric structure being located on the surface of the first thermoelectric structure and on the surface of the insulating layer adjacent to the first thermocouple layer.

[0012] Optionally, the method for forming silica aerogel in the cavity includes: mixing TEOS, ethanol, a light-blocking agent, and deionized water to form a precursor; mixing and stirring the precursor to form a sol solution; spraying the sol solution onto the substrate from the second surface to fill the cavity; allowing the sol solution to stand after spraying to gel at the substrate, forming a silica gel filling the cavity; aging the silica gel by immersing it in ethanol; immersing the aged silica gel in acetone for solvent replacement; drying the silica gel after solvent replacement to form a silica aerogel filling the cavity; and dicing and encapsulating the substrate after the above fabrication process.

[0013] Optionally, the molar ratio of TEOS, ethanol and deionized water is 1:4:4, the amount of the opacifier added is 5wt%~15wt%, and the standing time is 30 minutes.

[0014] Optionally, before spraying, the method for forming the sol solution further includes: adjusting the pH value of the precursor to a first target range using acetic acid; stirring the precursor with the pH value adjusted to the first target range at 20°C to 25°C for 45 minutes to form a transitional sol solution, wherein the first target range is a pH value of 2 to 3; adjusting the pH value of the transitional sol solution to a second target range using ammonia; and stirring the transitional sol solution with the pH value adjusted to the second target range at 20°C to 25°C for 15 minutes to form the sol solution, wherein the second target range is a pH value of 8 to 9.

[0015] Compared with the prior art, the technical solution of the present invention has the following beneficial effects: In the infrared thermopile sensor provided by the present invention, the cavity below the hot end of the infrared thermopile is filled with silica aerogel with a thermal conductivity lower than that of air. The reduction in thermal conductivity increases the heat preservation effect of the cavity, reduces the heat loss at the hot end, increases the temperature difference between the hot and cold ends, and thus improves the responsivity of the infrared device.

[0016] Furthermore, the addition of a light-blocking agent to the silica aerogel makes the thermal conductivity of the aerogel more stable at high temperatures, which can improve the linearity between the device's voltage output and temperature changes at high temperatures.

[0017] The method for fabricating an infrared thermopile sensor provided by the technical solution of this invention can fabricate the aforementioned infrared thermopile sensor, and therefore also possesses the technical effects of the aforementioned infrared thermopile sensor structure, which will not be elaborated further here. Meanwhile, the method for filling the cavity below the hot end of the infrared thermopile with silica aerogel is simple, low-cost, and has good compatibility with existing processes.

[0018] Furthermore, the immersion in hexamethyldisilazane (HMDSO) during the preparation process also changes the device itself from hydrophilic to hydrophobic, which can reduce the adhesion of water vapor in the environment and thus reduce the adverse effects of water vapor on device performance. Attached Figure Description

[0019] Figures 1 to 7 This is a schematic diagram of the structure of each step in the fabrication method of the infrared thermopile sensor provided by the present invention; Figure 8 This is a flowchart illustrating the preparation process of silica aerogel according to an embodiment of the present invention.

[0020] Explanation of reference numerals in the attached figures: 100, Substrate; 110, First surface; 120, Second surface; 130, Cavity; 200, Support layer; 310, First thermocouple layer; 320, Insulating layer; 321, Groove; 330, Second thermocouple layer; 331, First thermoelectric structure; 332, Second thermoelectric structure; 400, Passivation layer; 500, Silica aerogel; 600, Encapsulation substrate. Detailed Implementation

[0021] As described in the background section, current MEMS infrared thermopile devices use partial hollowing out of the substrate to increase the temperature difference between the cold and hot ends. Since infrared thermopile device packaging is typically performed at atmospheric pressure, the limited thermal conductivity of the air in the cavity causes some heat loss from the hot end, thus affecting the device's responsivity. This will be explained in detail below: On the one hand, temperature is a major factor affecting the temperature difference between the cold and hot ends. At room temperature, the thermal conductivity of air is 0.026 W / (m·K), which has limited heat preservation effect. Some of the heat from the hot end will still be lost through the cavity below the hot end, reducing the temperature difference between the cold and hot ends and causing a decrease in the responsivity of the infrared thermopile device. When the temperature rises significantly, the thermal conductivity of air increases with the temperature, increasing the heat loss from the hot end. When the temperature changes drastically, the thermal conductivity of air is insufficient to withstand the effects of a large temperature change rate, causing the hot end temperature to become inaccurate, resulting in an imbalance in the heat transfer efficiency between the cold and hot ends, and causing a nonlinear relationship between the voltage output generated by the device and the temperature.

[0022] On the other hand, humidity is another major factor affecting the temperature difference between the cold and hot ends. When the ambient humidity is high, water molecules enter the cavity, causing the thermal conductivity inside the cavity to increase, heat loss from the hot end to intensify, the temperature difference between the cold and hot ends to decrease, and the device performance to deteriorate.

[0023] To address the aforementioned technical problems, the present invention provides a MEMS infrared thermopile sensor and its fabrication method. By filling the cavity below the hot end of the infrared thermopile with silica aerogel whose thermal conductivity is lower than that of air, heat loss from the hot end is reduced, thereby increasing the temperature difference between the hot and cold ends, and thus improving the responsivity and performance of the infrared device.

[0024] To make the above-mentioned objectives, features, and beneficial effects of the present invention more apparent and understandable, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] The terms “first,” “second,” “third,” “fourth,” etc. (if present) in the specification, claims, and drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a particular order or sequence. It should be understood that such data can be interchanged where appropriate so that embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms “comprising” and “having,” and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus. Additionally, directional terms such as above, below, up, down, upward, downward, left, right, etc., are used relative to exemplary embodiments as they are shown in the figures, with upward or upper directions pointing towards the top of the corresponding figure and downward or lower directions pointing towards the bottom of the corresponding figure.

[0026] Figures 1 to 7 This is a schematic diagram of the structure of each step in the fabrication method of the infrared thermopile sensor provided by the present invention.

[0027] Please refer to Figure 1 A substrate 100 is provided, which may include a first surface 110 and a second surface 120 opposite to each other.

[0028] Specifically, the substrate 100 is made of silicon. The substrate 100 may also include at least one of the following materials: Ge, SiGe, SiC, SiGeC, InAs, GaAs, InP, InGaAs, or other III / V compound semiconductors. Alternatively, the substrate 100 may include a silicon substrate, silicon-on-insulator (SSOI), silicon-on-insulator (S-SiGeOI), silicon-on-insulator (SiGeOI), or germanium-on-insulator (GeOI), etc. The size of the substrate 100 may be 6 inches, 8 inches, 12 inches, etc., and there is no limitation thereto.

[0029] Please continue to refer to this. Figure 1 A support layer 200 is deposited on the first surface 110 of the substrate 100.

[0030] Specifically, the method for forming the support layer 200 includes: sequentially forming a SiO2, SiN and SiO2 sandwich structure film layer on the first surface 110 of the substrate 100 to form an ONO (Oxide-Nitride-Oxide) structure as the support layer 200.

[0031] The support layer 200 can also be a double-layer structure of SiO2 and SiN or a single-layer structure of SiO2.

[0032] Next, a thermopile device layer is formed on the top surface of the support layer 200.

[0033] In this embodiment, the thermopile device layer may include: a first thermocouple layer 310, an insulating layer 320, and a second thermocouple layer 330.

[0034] The following combination Figure 2 and Figure 3 The specific steps for forming the thermopile device layer are explained in detail.

[0035] Please refer to Figure 2 A patterned first thermocouple layer 310 is formed on the top surface of a portion of the support layer 200.

[0036] The first thermocouple layer 310 is used as the hot end of the thermopile in the MEMS infrared thermopile sensor.

[0037] In this embodiment, the material of the first thermocouple layer 310 can be polycrystalline silicon.

[0038] In this embodiment, the method for forming the first thermocouple layer 310 may include: depositing a layer of polysilicon on the top surface of a portion of the support layer 200; performing ion implantation on the deposited polysilicon layer; and after ion implantation, performing masked etching on the deposited polysilicon layer to remove excess areas and form the first thermocouple layer 310.

[0039] Furthermore, the ion implantation type is N-type.

[0040] Specifically, the N-type ion is phosphorus.

[0041] Please continue to refer to this. Figure 2 An insulating layer 320 is formed on the top surface of the first thermocouple layer 310.

[0042] Specifically, the method of forming the insulating layer 320 may include depositing the insulating layer 320 on the top surface of the first thermocouple layer 310 and the exposed support layer 200, wherein the surface of the insulating layer 320 is higher than the surface of the first thermocouple layer 310.

[0043] Specifically, the material of the insulating layer 320 may include SiO2.

[0044] Please continue to refer to this. Figure 2 The insulating layer 320 is etched to form a groove 321.

[0045] In this embodiment, the bottom surface of the groove 321 exposes the top surface of the first thermocouple layer 310.

[0046] In this embodiment, the etching process for the insulating layer 320 can be a wet etching process or a dry etching process.

[0047] Please refer to Figure 3 and Figure 4 A second thermocouple layer 330 is formed in the groove 321 and on part of the top surface of the insulating layer 320, and the second thermocouple layer 330 is connected to the first thermocouple layer 310.

[0048] In this embodiment, the second thermocouple layer 330 is used as a conductive structure of the thermopile and as the cold end of the thermopile.

[0049] In this embodiment, the second thermocouple layer 330 may include: a first thermoelectric structure 331 and a second thermoelectric structure 332.

[0050] The first thermoelectric structure 331 penetrates the interior of the insulating layer 320 and is in contact with the first thermocouple layer 310. The second thermoelectric structure 332 is located on the surface of the first thermoelectric structure 331 and on the surface of the insulating layer 320 adjacent to the first thermocouple layer 310.

[0051] Please refer to Figure 3 Metal is deposited in the groove 321 and on the top surface of the insulating layer 320. Then, the metal deposited on the top surface of the insulating layer 320 is etched to form a first thermoelectric structure 331 that penetrates the interior of the insulating layer 320 and a second thermoelectric structure 332 located on the surface of the first thermoelectric structure 331 and on the surface of the insulating layer 320 adjacent to the first thermocouple layer 310.

[0052] Specifically, metallic materials can include gold.

[0053] Please refer to Figure 4 A passivation layer 400 is formed on the top surface of the thermopile device layer.

[0054] Since an insulating dielectric thin film passivation layer 400 is formed on the top surface of the thermopile device layer, the passivation layer 400 can serve as a passivation protection layer, improving the stability and lifespan of the device.

[0055] In this embodiment, while forming the passivation layer, the top surface of the second thermoelectric structure 332 is exposed to form an exposed surface, and the exposed surface of the second thermoelectric structure 332 can serve as a solder pad.

[0056] Specifically, the method for forming the passivation layer 400 may include: depositing a passivation material film on the top surface of the thermopile device layer, the passivation material film completely covering the top surface of the thermopile device layer; forming a patterned passivation mask layer on the surface of the passivation material film; using the patterned passivation mask layer as a mask, etching the passivation material film to form the passivation layer 400, the passivation layer 400 exposing part of the top surface of the second thermoelectric structure 332.

[0057] Among them, part of the top surface of the second thermoelectric structure 332 is an exposed surface, and the orthographic projection of the second thermoelectric structure 332 and its corresponding first thermoelectric structure 331 on the exposed surface on the substrate 100 does not overlap with the orthographic projection of the cavity 130 on the substrate 100.

[0058] In this embodiment, the second thermoelectric structure 332 on the exposed surface and its corresponding first thermoelectric structure 331 are used as the cold junction of the second thermocouple layer 330.

[0059] Specifically, the passivation layer 400 can be made of SiN. Since SiN has a certain infrared absorption capability, the performance of the device will also be improved.

[0060] Please refer to Figure 5 The substrate 100 is etched from the second surface of the substrate 100 until the bottom surface of the support layer 200 is exposed, forming a cavity 130.

[0061] Specifically, the method for forming the cavity 130 may include: performing deep silicon etching on the substrate 100 from the second surface of the substrate 100; and performing resist removal and cleaning after etching to form the cavity 130 that exposes the bottom surface of the support layer 200.

[0062] In this embodiment, the deep silicon etching process can be the Bosch process.

[0063] Preferably, before deep silicon etching, the second side of the substrate 100 can be thinned to reduce the etching depth and package size.

[0064] Please refer to Figure 6 500 silica aerogel is formed inside the cavity.

[0065] In this embodiment, the silica aerogel 500 contains a light-blocking agent, and the amount of the light-blocking agent added to the silica aerogel 500 is 5wt%~15wt%.

[0066] Specifically, the light-blocking agent is one or more of zirconium oxide, titanium oxide, silicon carbide, and potassium titanate, and the particle size of the light-blocking agent is 20 nm to 500 nm.

[0067] The choice of opaque agent can be made according to the operating environment of the device. In environments below 600°C and in oxidizing atmospheres (such as air), titanium dioxide or silicon carbide can be selected as opaque agents. In environments between 600°C and 1000°C and in oxidizing atmospheres (such as air), titanium dioxide can be selected. In environments above 1000°C and in oxidizing atmospheres (such as air), zirconium oxide must be selected.

[0068] In addition, the selection of opaque agents can also involve the use of nano opaque agents of various particle sizes to achieve the widest spectral range of opaque effect.

[0069] Please refer to Figure 8 The method for forming silica aerogel 500 within cavity 130 may include: Step 1: Mix TEOS, ethanol, opacifier and deionized water to form a precursor.

[0070] Step 2: Mix and stir the precursors to form a sol solution.

[0071] Step 3: Spray the sol solution onto the substrate from the second side 120 so that the sol solution fills the cavity 130.

[0072] Step four: After spraying, allow the solution to stand to gel, forming a silica gel that fills the cavity 130.

[0073] Step 5: Immerse the silica gel in ethanol for aging treatment.

[0074] Step 6: Immerse the aged silica gel in acetone for solvent replacement treatment.

[0075] Step 7: Dry the silica gel after solvent replacement treatment to form silica aerogel 500 that fills the cavity 130.

[0076] Step 8: Divide and package the substrate that has completed the above manufacturing process.

[0077] Furthermore, in step one, the molar ratio of TEOS, ethanol, and deionized water is 1:4:4.

[0078] Specifically, TEOS, ethanol, and deionized water are mixed in a molar ratio of 1:4:4, and then 8wt% of nano-sized zirconium oxide is added to form a precursor.

[0079] In this embodiment, the precursor is subjected to strong ultrasonication for 30 minutes and stirred for 30 minutes to form a sol solution.

[0080] Furthermore, prior to step three, the method for forming silica aerogel 500 within cavity 130 may also include the following operations.

[0081] The pH of the sol solution was adjusted to the first target range using acetic acid.

[0082] The sol solution with pH adjusted to the first target range is stirred at 20℃~25℃ for 45 minutes to form a transition sol solution. The first target range is a pH of 2~3.

[0083] The pH of the transition sol solution was adjusted to the second target range using ammonia.

[0084] The transition sol solution with pH adjusted to the second target range was stirred at 20°C to 25°C for 15 minutes. The second target range is a pH of 8 to 9.

[0085] Specifically, the pH of the above sol solution was adjusted to 2-3 with acetic acid and stirred at 20-25°C for 45 minutes. Then, ammonia was added to adjust the pH to 8-9, and the solution was stirred at 20-25°C for 15 minutes. Acetic acid and ammonia have mild acidity and alkalinity, which can effectively catalyze the reaction while avoiding runaway reaction, ultimately forming a sol solution with uniform SiO2 particles and stable dispersion of the opacifier, laying the foundation for subsequent gelation.

[0086] Specifically, the sol solution treated with acetic acid and ammonia is sprayed from the second surface 120 onto the substrate 100. The thickness of the sprayed sol solution is slightly higher than the depth of the cavity 130, so that the sol solution fills the cavity 130 completely.

[0087] Specifically, the cavity 130 is placed upward in a sealed environment at 30°C and left to stand, allowing the sol solution sprayed on the substrate 100 to gel, forming a silica gel 500 that fills the cavity 130.

[0088] Furthermore, the settling time is 30 minutes.

[0089] Specifically, the silica gel was soaked in ethanol for 24 hours for aging treatment, and then the aged silica gel was soaked in acetone. The acetone solvent was changed every 12 hours, and this process was repeated 4 times to replace the liquid in the pores of the silica gel with acetone.

[0090] Furthermore, before proceeding to step seven, the silica gel that has undergone solvent displacement treatment is immersed in hexamethyldisilazane for 12 hours.

[0091] Specifically, the silica gel after solvent replacement treatment is immersed in hexamethyldisilazane for 12 hours, and then placed in a well-ventilated environment at 50°C for 48 hours to dry, forming silica aerogel 500 that fills the cavity 130. Subsequently, the substrate that has completed the above preparation process is diced and cut, and the substrate 600 is bonded and encapsulated.

[0092] Accordingly, embodiments of the present invention also provide an infrared thermopile sensor formed based on the above-described method for preparing an infrared thermopile sensor.

[0093] Please refer to Figure 7 The infrared thermopile sensor includes: a substrate 100, a support layer 200, a thermopile device layer, and a passivation layer 400.

[0094] The substrate 100 includes a first surface 110 and a second surface 120 opposite to each other, and the substrate 100 has a cavity 130 exposed by the second surface.

[0095] In this embodiment, the support layer 200 is located on the first surface 110, and the bottom of the cavity 130 exposes the bottom surface of the support layer 200.

[0096] In this embodiment, the thermopile device layer is located on the top surface of the support layer 200.

[0097] In this embodiment, the thermopile device layer includes a first thermocouple layer 310, an insulating layer 320, and a second thermocouple layer 330.

[0098] In this embodiment, the first thermocouple layer 310 is located on the top surface of the support layer 200, and the first thermocouple layer 310 is used as the hot end of the thermopile.

[0099] In this embodiment, the insulating layer 320 is located on the top surface of the first thermocouple layer 310.

[0100] In this embodiment, the second thermocouple layer 330 is located on the surface of the insulating layer 320 and a portion of the first thermocouple layer 310. The second thermocouple layer 330 includes a first thermoelectric structure 331 and a second thermoelectric structure 332. The first thermoelectric structure 331 penetrates the insulating layer 320 and is in contact with the first thermocouple layer 310. The second thermoelectric structure 332 is located on the surface of the first thermoelectric structure 331 and on the surface of the insulating layer 320 adjacent to the first thermocouple layer 310. The passivation layer 400 exposes a portion of the surface of the second thermoelectric structure 332. The orthographic projection of the exposed surface of the second thermoelectric structure 332 and its corresponding first thermoelectric structure 331 on the substrate 100 does not overlap with the orthographic projection of the cavity 130 on the substrate 100. The exposed surface of the second thermoelectric structure 332 and its corresponding first thermoelectric structure 331 are used as the cold end of the thermoelectric stack.

[0101] In this embodiment, the passivation layer 400 is located on the top surface of the thermopile device layer.

[0102] Furthermore, the infrared thermopile sensor may also include: a packaging substrate 600, which is located on the second side 120 of the substrate 100.

[0103] Specifically, the materials, forming process, working principle, specific implementation method and beneficial effects of the infrared thermopile sensor in the embodiments of the present invention can be found in the preparation method of the infrared thermopile sensor in the embodiments of the present invention, and will not be repeated here.

[0104] While the present invention has been disclosed above, it is not limited thereto. Any person skilled in the art can make various modifications and alterations without departing from the spirit and scope of the invention; therefore, the scope of protection of the present invention should be determined by the scope defined in the claims.

Claims

1. A MEMS infrared thermopile sensor, characterized in that, include: A substrate, the substrate including opposing first and second surfaces, the substrate having a cavity formed on the second surface; A support layer is located on the first surface, and the cavity penetrates the substrate and exposes the bottom surface of the support layer; A thermopile device layer, wherein the thermopile device layer is located on the top surface of the support layer; A passivation layer, the passivation layer being located on a portion of the top surface of the thermopile device layer; The silica aerogel is located within the cavity, and the thermal conductivity of the silica aerogel is lower than that of air.

2. The MEMS infrared thermopile sensor as described in claim 1, characterized in that, The thermopile device layer includes: A first thermocouple layer is located on the top surface of the support layer, and the first thermocouple layer is used as the hot end of the thermopile. An insulating layer is located on the top surface of the first thermocouple layer; The second thermocouple layer includes a first thermoelectric structure and a second thermoelectric structure. The first thermoelectric structure penetrates the insulating layer and is in contact with the first thermocouple layer. The second thermoelectric structure is located on the surface of the first thermoelectric structure and on the surface of the insulating layer adjacent to the first thermocouple layer. The passivation layer exposes a portion of the surface of the second thermoelectric structure. The orthographic projection of the second thermoelectric structure on the exposed surface and its corresponding first thermoelectric structure on the substrate does not overlap with the orthographic projection of the cavity on the substrate. The second thermoelectric structure on the exposed surface and its corresponding first thermoelectric structure are used as the cold end of the thermopile.

3. The MEMS infrared thermopile sensor as described in claim 2, characterized in that, The first thermocouple layer is made of polycrystalline silicon, the insulating layer is made of silicon dioxide, and the second thermocouple layer is made of gold.

4. The MEMS infrared thermopile sensor as described in claim 1, characterized in that, The silica aerogel contains a light-blocking agent, which is one or more of zirconium oxide, titanium oxide, silicon carbide and potassium titanate, and the particle size of the light-blocking agent is 20 nm to 500 nm.

5. The MEMS infrared thermopile sensor as described in claim 1, characterized in that, Also includes: A packaging substrate, wherein the packaging substrate is located on the second side of the substrate.

6. A method for fabricating a MEMS infrared thermopile sensor, characterized in that, include: A substrate is provided, the substrate including opposing first and second surfaces; A support layer is deposited on the first surface of the substrate; A thermopile device layer is formed on the top surface of the support layer; A passivation layer is formed on the top surface of the thermopile device layer; The substrate is etched from its second surface until the bottom surface of the support layer is exposed, forming a cavity; A silica aerogel is formed inside the cavity.

7. The method for fabricating a MEMS infrared thermopile sensor as described in claim 6, characterized in that, The method of forming the thermopile device layer on the top surface of the support layer includes: A patterned first thermocouple layer is formed on the top surface of a portion of the support layer; An insulating layer is formed on the top surface of the first thermocouple layer and the exposed support layer; The insulating layer is etched to form a groove, the bottom surface of which exposes the top surface of the first thermocouple layer; A second thermocouple layer is formed within the groove and on a portion of the top surface of the insulating layer. The second thermocouple layer includes a first thermoelectric structure and a second thermoelectric structure. The first thermoelectric structure penetrates the insulating layer and is in contact with the first thermocouple layer. The second thermoelectric structure is located on the surface of the first thermoelectric structure and on the surface of the insulating layer adjacent to the first thermocouple layer.

8. The method for fabricating a MEMS infrared thermopile sensor as described in claim 6, characterized in that, The method for forming silica aerogel within the cavity includes: A precursor is formed by mixing TEOS, ethanol, a light-blocking agent, and deionized water. The precursors are mixed and stirred to form a sol solution; The sol solution is sprayed onto the substrate from the second surface, so that the sol solution fills the cavity. After the spraying, the solution is allowed to stand to gel, forming a silica gel that fills the cavity. The silica gel was immersed in ethanol for aging treatment; The aged silica gel was immersed in acetone for solvent replacement treatment. The silica gel after solvent replacement treatment is dried to form a silica aerogel that fills the cavity. The substrate that has completed the above manufacturing process is then diced and packaged.

9. The method for fabricating a MEMS infrared thermopile sensor as described in claim 8, characterized in that, The molar ratio of TEOS, ethanol and deionized water is 1:4:4, the amount of the opacifier added is 5wt%~15wt%, and the standing time is 30 minutes.

10. The method for fabricating a MEMS infrared thermopile sensor as described in claim 8, characterized in that, The method for forming the sol solution prior to the spraying process further includes: The pH value of the precursor was adjusted to the first target range using acetic acid. The precursor with pH adjusted to the first target range was stirred at 20°C to 25°C for 45 minutes to form a transitional sol solution. The first target range is a pH of 2 to 3. The pH of the transition sol solution was adjusted to the second target range using ammonia water; The transition sol solution with pH adjusted to the second target range is stirred at 20°C to 25°C for 15 minutes to form the sol solution, wherein the second target range is a pH of 8 to 9.

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