Micro-electro-mechanical system semiconductor gas sensor and method of manufacturing the same

Abstract

The application discloses a micro-electro-mechanical system semiconductor gas sensor and a preparation method thereof. The preparation method of the micro-electro-mechanical system semiconductor gas sensor comprises the following steps: mixing a metal oxide semiconductor gas-sensitive material, a binder and a dispersing agent, performing at least one grinding to prepare a slurry; providing a mask plate, the mask plate is provided with a plurality of grooves corresponding to the size of the micro-electro-mechanical system sensor, and a micro-electro-mechanical system sensor is arranged in each groove; providing a drop coating device, the drop coating device is provided with a plurality of needle heads corresponding to the positions of the grooves, the slurry is dropped from the needle heads to the surface of the micro-electro-mechanical system sensor in the grooves, and drying is performed. Through the positioning cooperation of the mask plate and the drop coating process, the synchronous film forming of the plurality of micro-electro-mechanical system sensors can be realized, the film layer morphology, the thickness and the sensing performance of the plurality of devices are effectively guaranteed to be highly unified, and the small-batch trial production and the large-scale production requirements of the micro-electro-mechanical system semiconductor gas sensor are met.

Description

Technical Field

[0001] This application relates to the field of gas sensors, and in particular to a microelectromechanical system (MEMS) semiconductor gas sensor and its fabrication method. Background Technology

[0002] The rapid development of MEMS (Micro-Electro-Mechanical Systems) semiconductor gas sensors has driven the upgrading of gas-sensitive material deposition processes from traditional thick-film coating to silicon-based miniaturization, wafer-level processing, and CMOS compatibility. To adapt to the requirements of micro-hotplate structures and low power consumption and high consistency, deposition technologies have evolved from early solution methods such as spin coating and spraying to patterned processes such as inkjet printing and screen printing, and further towards vapor deposition methods such as magnetron sputtering, chemical vapor deposition (CVD), and atomic layer deposition (ALD). Among these, atomic layer deposition (ALD), with its advantages of atomic-level thickness control, high uniformity, and step coverage, has become a core deposition technology for high-end chips. In recent years, composite deposition methods such as in-situ hydrothermal growth and electrospinning have emerged, improving the specific surface area and stability of sensitive films while achieving deep integration with MEMS processes, strongly supporting the large-scale application of high-precision, low-power gas sensing in fields such as lithium battery safety and environmental monitoring.

[0003] Traditionally, gas-sensitive materials are formed on MEMS using methods including solution deposition and vapor deposition. However, traditional solution deposition processes such as sol-gel spin coating and spraying rely heavily on manual or semi-manual operation, making it difficult to achieve uniform coverage on microstructures such as MEMS hotplates. The resulting gas-sensitive films suffer from large thickness deviations, rough surface morphology, and inhomogeneous microstructures. During subsequent high-temperature annealing, defects such as cracking, warping, and peeling easily occur. Batch repeatability is poor, and consistency is difficult to guarantee, making them only suitable for small-batch sample preparation in the laboratory and unable to meet the requirements of industrial mass production. While vapor deposition technologies such as magnetron sputtering and physical vapor deposition (PVD) have improved film uniformity and adhesion, they require high vacuum environments, involve high equipment investment, complex processes, and long pretreatment and deposition cycles. Furthermore, they have limited ability to cover the steps of three-dimensional microstructures, making it difficult to balance high specific surface area with mass production efficiency. Summary of the Invention

[0004] Therefore, it is necessary to provide a microelectromechanical system semiconductor gas sensor with uniform film formation, short process cycle, and suitable for mass production, as well as its preparation method.

[0005] This application provides a method for fabricating a semiconductor gas sensor for a microelectromechanical system, comprising the following steps:

[0006] A slurry is prepared by mixing a metal oxide semiconductor gas-sensitive material, a binder, and a dispersant, and then grinding it at least once.

[0007] A mask is provided, wherein a plurality of grooves corresponding to the size of a microelectromechanical system (MEMS) sensor are provided on the mask, and a MEMS sensor is placed in each groove;

[0008] A drop-coating device is provided, which is equipped with a plurality of needles corresponding to the positions of the grooves, and the slurry is drop-coated from the needles onto the surface of the microelectromechanical system sensor in the grooves and then dried.

[0009] In one embodiment, the conditions for each grinding independently include one or two of the following conditions:

[0010] (1) The grinding speed is 800 rpm to 1500 rpm;

[0011] (2) The grinding time is 10 min to 45 min.

[0012] In one embodiment, the slurry further includes a solvent, and the slurry comprises the metal oxide semiconductor gas-sensitive material, the binder, the dispersant, and the solvent in a mass ratio of (3~15):(0.5~3):(0.5~3):(80~96).

[0013] In one embodiment, the metal oxide semiconductor gas-sensitive material comprises tin dioxide.

[0014] In one embodiment, the adhesive comprises one or more of glass powder, epoxy resin, and polyethylene glycol.

[0015] In one embodiment, the dispersant includes one or more of ethyl cellulose, citric acid, and polyvinylpyrrolidone.

[0016] In one embodiment, the solvent includes one or more of isopropanol, methanol, terpineol, ethanol, and water.

[0017] In one embodiment, the drop-coating conditions satisfy one or more of the following conditions:

[0018] (1) Dropping speed: 0.5 mm / s ~ 1.5 mm / s;

[0019] (2) The drop-coating time is 100ms~200ms;

[0020] (3) The dripping pressure is 0.8 kPa to 1.2 kPa.

[0021] In one embodiment, drying satisfies one or both of the following conditions:

[0022] (1) The drying temperature is 50℃~80℃;

[0023] (2) The drying time is 5 min to 15 min.

[0024] This application also provides a microelectromechanical system (MEMS) semiconductor gas sensor, which is prepared according to the above-described method for preparing a MEMS semiconductor gas sensor.

[0025] The fabrication method of the microelectromechanical system (MEMS) semiconductor gas sensor provided in this application can achieve simultaneous film formation of multiple MEMS sensors by using mask positioning and drop coating process. The whole process is short, easy to operate and the parameters are easy to control. It effectively ensures that the film morphology, thickness and sensing performance of multiple devices are highly uniform, which meets the needs of small-batch trial production and large-scale production of MEMS semiconductor gas sensors. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 The images show a comparison before and after coating. (a) is before coating and (b) is after coating. Detailed Implementation

[0028] To facilitate understanding of this application, a more complete description will be provided below. This application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure of this application.

[0029] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0030] As used herein, the term "and / or" encompasses any one of two or more of the related listed items, as well as any and all combinations of the related listed items. These arbitrary and all combinations include any two related listed items, any more related listed items, or a combination of all related listed items. For example, "A and / or B" includes three parallel options: A, B, and "a combination of A and B".

[0031] In this document, unless otherwise stated, "one or more" means any one of the listed items or any combination of the listed items. Similarly, "one or more" and other instances of "one or more" are to be understood in the same way unless otherwise stated.

[0032] In this document, terms such as "further," "even further," "especially," "for example," "like," "example," and "exemplary" are used for descriptive purposes to indicate a connection in the coverage of different technical solutions presented earlier and later. However, they should not be construed as limitations on the preceding technical solution or on the scope of protection of this document. Unless otherwise specified, in this document, A (e.g., B) indicates that B is a non-limiting example of A, and it can be understood that A is not limited to B.

[0033] In this document, "optionally," "optionally," and "optional" mean that something is optional, that is, it is selected from either "present" or "absent." If multiple "options" appear in a technical solution, unless otherwise specified and there are no contradictions or mutual constraints, each "option" is independent. In this application, descriptions such as "optionally contains" and "optionally includes" indicate "contains or does not contain." "Optional component X" indicates whether component X exists or does not exist, or whether component X is contained or not.

[0034] In this document, the terms "first aspect," "second aspect," "third aspect," and "fourth aspect," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or quantity, nor should they be construed as implicitly indicating the importance or quantity of the indicated technical features. Moreover, "first," "second," "third," and "fourth" serve only as a non-exhaustive enumeration and should be understood as not constituting a closed limitation on quantity.

[0035] In this article, the technical features described in an open-ended manner include both closed technical solutions composed of the listed features and open technical solutions that include the listed features.

[0036] In this document, when referring to numerical intervals (i.e., numerical ranges), unless otherwise specified, the distribution of selectable values ​​within a numerical interval is considered continuous, and includes the two endpoints (i.e., the minimum and maximum values) of the numerical interval, as well as every value between these two endpoints. Unless otherwise specified, when a numerical interval refers only to integers within that interval, it includes the two endpoint integers of the numerical range, as well as every integer between the two endpoints, which is equivalent to directly listing every integer. When multiple numerical ranges are provided to describe features or characteristics, these numerical ranges can be merged. In other words, unless otherwise specified, the numerical ranges disclosed herein should be understood to include any and all subranges included therein. The "numerical value" in this numerical interval can be any quantitative value, such as a number, percentage, ratio, etc. The term "numerical interval" can be broadly included to include percentage intervals, ratio intervals, proportion intervals, and other numerical interval types.

[0037] In this document, the terms "room temperature" or "normal temperature" generally refer to 4°C to 35°C, for example, 20°C ± 5°C. In some embodiments of this document, "room temperature" or "normal temperature" refers to 10°C to 30°C. In some embodiments of this document, "room temperature" or "normal temperature" refers to 20°C to 30°C.

[0038] In this document, for methods involving multiple steps, unless otherwise explicitly stated herein, there is no strict order constraint on the execution of these steps; they may be executed in any order other than those described. Moreover, any step may include multiple sub-steps or multiple stages, which are not necessarily completed at the same time, but may be executed at different times, and their execution order is not necessarily sequential, but may be executed in turn, alternately, or simultaneously with other steps or parts of the sub-steps or stages of other steps.

[0039] This application provides a method for fabricating a semiconductor gas sensor for a microelectromechanical system, comprising the following steps:

[0040] A slurry is prepared by mixing a metal oxide semiconductor gas-sensitive material, a binder, and a dispersant, and then grinding it at least once.

[0041] A mask is provided, which has multiple grooves corresponding to the size of a microelectromechanical system (MEMS) sensor, and a MEMS sensor is placed in each groove;

[0042] A drop-coating device is provided, which is equipped with multiple needles corresponding to the positions of the grooves. The slurry is drop-coated from the needles onto the surface of the microelectromechanical system sensor in the groove and then dried.

[0043] The fabrication method of the microelectromechanical system (MEMS) semiconductor gas sensor provided in this application can achieve simultaneous film formation of multiple MEMS sensors by using mask positioning and drop coating process. The whole process is short, easy to operate and the parameters are easy to control. It effectively ensures that the film morphology, thickness and sensing performance of multiple devices are highly uniform, which meets the needs of small-batch trial production and large-scale production of MEMS semiconductor gas sensors.

[0044] In some specific examples, the grinding speed is 800 rpm to 1500 rpm per cycle. Specifically, the grinding speed per cycle can be, but is not limited to, 800 rpm, 900 rpm, 1000 rpm, 1100 rpm, 1200 rpm, 1300 rpm, 1400 rpm, or 1500 rpm. The grinding time per cycle is 10 min to 45 min. Specifically, the grinding time per cycle can be, but is not limited to, 10 min, 15 min, 20 min, 25 min, 30 min, 35 min, 40 min, or 45 min.

[0045] Understandably, grinding involves one forward rotation and one reverse rotation. The selection of grinding speed and time for each rotation must balance the uniformity of slurry dispersion and preparation efficiency. If the speed is too low or the time is too short, the particles will not be sufficiently dispersed, and agglomeration will occur in the slurry. If the speed is too high or the time is too long, excessive solvent evaporation may occur, increasing the viscosity of the slurry and affecting the subsequent drop coating effect.

[0046] In some specific examples, the slurry also includes a solvent, and the slurry includes a gas-sensitive material, a binder, a dispersant and a solvent in a mass ratio of (3~15):(0.5~3):(0.5~3):(80~96).

[0047] In some specific examples, metal oxide semiconductor gas-sensitive materials include tin dioxide (SnO2). It is understood that metal oxide semiconductor gas-sensitive materials are sensitive film materials used in MEMS semiconductor gas sensors.

[0048] In some specific examples, the adhesive includes one or more of glass powder, epoxy resin, and polyethylene glycol. The adhesive is used to enhance the adhesion between the gas-sensitive material and the MEMS semiconductor gas sensor substrate, improving the structural stability of the thin film.

[0049] In some specific examples, the dispersant includes one or more of ethyl cellulose, citric acid, and polyvinylpyrrolidone. The dispersant is used to improve the dispersibility of particles in the slurry, prevent particle agglomeration, and ensure the uniformity of the drop-coated film.

[0050] In some specific examples, the solvent includes one or more of isopropanol, methanol, terpineol, ethanol, and water. The solvent is used to adjust the viscosity and flowability of the slurry, making it suitable for drop coating processes.

[0051] A photomask is provided, having multiple grooves corresponding to the dimensions of microelectromechanical system (MEMS) sensors. One MEMS sensor is placed in each groove. Understandably, the array of grooves on the photomask enables synchronous positioning of multiple MEMS sensors, allowing for batch coating operations to be completed in a single setup, significantly improving production efficiency.

[0052] A drop-coating device is provided, which is equipped with multiple needles corresponding to the positions of the grooves. The slurry is drop-coated from the needles onto the surface of the microelectromechanical system sensor in the groove and then dried.

[0053] In some specific examples, the droplet speed is 0.5 mm / s to 1.5 mm / s. Specifically, the droplet speed can be, but is not limited to, 0.5 mm / s, 0.6 mm / s, 0.7 mm / s, 0.8 mm / s, 0.9 mm / s, 1.0 mm / s, 1.1 mm / s, 1.2 mm / s, 1.3 mm / s, 1.4 mm / s, or 1.5 mm / s.

[0054] Understandably, the drop rate controls the amount of slurry deposited, affecting the uniformity of film thickness. If the rate is too fast, the amount of slurry deposited will be insufficient, resulting in a thin and uneven film; if the rate is too slow, too much slurry will be deposited, which may lead to an excessively thick film or overflow.

[0055] In some specific examples, the drop-coating time is 100ms to 200ms. Specifically, the drop-coating time can be, but is not limited to, 100ms, 110ms, 120ms, 130ms, 140ms, 150ms, 160ms, 170ms, 180ms, 190ms, or 200ms.

[0056] In some specific examples, the drop-coating pressure is 0.8 kPa to 1.2 kPa. Specifically, the drop-coating pressure can be, but is not limited to, 0.8 kPa, 0.9 kPa, 1 kPa, 1.1 kPa, or 1.2 kPa.

[0057] In some specific examples, the drying temperature is 50°C to 80°C. Specifically, the drying temperature may be, but is not limited to, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, or 80°C. The drying time is 5 min to 15 min. Specifically, the drying time may be, but is not limited to, 5 min, 6 min, 7 min, 8 min, 9 min, 10 min, 11 min, 12 min, 13 min, 14 min, or 15 min.

[0058] Understandably, the choice of drying temperature needs to take into account both the solvent evaporation rate and the quality of the film. If the temperature is too low, solvent residue will result in a loose film, while if the temperature is too high, the solvent will evaporate too quickly, causing the film to crack.

[0059] This application also provides a microelectromechanical system (MEMS) semiconductor gas sensor, which is prepared according to the above-described method for preparing a MEMS semiconductor gas sensor.

[0060] It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of this application. For experimental methods in the following embodiments where specific conditions are not specified, please refer to the guidelines given in this application, or follow experimental manuals or conventional conditions in the field, or follow the conditions recommended by the manufacturer, or refer to experimental methods known in the field.

[0061] In the specific embodiments described below, the measurement parameters involving raw material components may have slight deviations within the weighing accuracy range unless otherwise specified. Temperature and time parameters are subject to acceptable deviations due to instrument testing accuracy or operational precision.

[0062] Example 1

[0063] This embodiment provides a method for fabricating a semiconductor gas sensor for a microelectromechanical system (MEMS), including the following steps:

[0064] S1. Pretreatment of the drop-coating material: The prepared gas-sensitive material SnO2, binder glass powder, dispersant ethyl cellulose, and solvent terpineol were sequentially placed into a ball mill jar in a ratio of 0.04g:0.005g:0.005g:0.8ml. The ball mill jar was placed in a vacuum chamber for vacuum treatment, and then placed in the groove of the ball mill. Accessories were installed and secured with screws. The ball mill parameters were set as follows: rotation speed 1000rpm, grinding time 30min. After ball milling, the slurry was transferred to a glass bottle for storage and later use.

[0065] S2. Mounting and Positioning: Use a pipette to transfer the slurry prepared in step S1 into a syringe. The syringe should have a nominal outer diameter of 0.16 mm. Then, install the syringe into the automatic dispensing machine. Open the protective cover of the dispensing machine and use tweezers to place the MEMS sensor into the groove of the mask. The mask has overall dimensions of 97.32 mm × 97.32 mm and a thickness of 6 mm. It is divided into 10 rows, with 10 grooves per row, for a total of 100 grooves. Each groove measures 5.1 mm × 5.1 mm and has a depth of 1.63 mm. The MEMS sensor measures 5 mm × 5 mm and has a thickness of 1 mm.

[0066] S3. Automatic Dispensing: Turn on the host computer and connect it to the automatic dispensing machine using dedicated software. After successful connection, perform debugging and set the dispensing parameters: dispensing speed 1.00 mm / s, dispensing air pressure 1.0 kPa, normal air pressure -0.1 kPa, start time 150 ms, end time 0 ms. Start dispensing; the slurry is precisely dispensed onto the surface of the MEMS sensor.

[0067] S4. Drying and film formation: Place the MEMS sensor after drop coating into an oven at 60°C and dry for 10 minutes to complete the film formation of the gas-sensitive material on the surface of the MEMS sensor.

[0068] like Figure 1 The images shown are before and after coating: (a) before coating and (b) after coating.

[0069] Example 2

[0070] This embodiment provides a method for preparing a semiconductor gas sensor for microelectromechanical systems. The steps are the same as in Embodiment 1, except that in step S1, the solvent is replaced with ethanol, while the solvent mass remains unchanged.

[0071] Example 3

[0072] This embodiment provides a method for preparing a semiconductor gas sensor for microelectromechanical systems. The steps are the same as in Embodiment 1, except that in step S1, the solvent is replaced with isopropanol, while the solvent mass remains unchanged.

[0073] Example 4

[0074] This embodiment provides a method for preparing a semiconductor gas sensor for microelectromechanical systems. The steps are the same as in Embodiment 1, except that in step S1, the solvent is replaced with methanol while the solvent mass remains unchanged.

[0075] The above embodiments merely illustrate several implementation methods of this application to facilitate a detailed understanding of the technical solutions of this application, but should not be construed as limiting the scope of protection of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the scope of protection of this application. It should be understood that technical solutions obtained by those skilled in the art based on the technical solutions provided in this application through logical analysis, reasoning, or limited experimentation are all within the scope of protection of the appended claims. Therefore, the scope of protection of this patent application should be determined by the content of the appended claims, and the specification can be used to interpret the content of the claims.

Claims

1. A method for fabricating a microelectromechanical system (MEMS) semiconductor gas sensor, characterized in that, Includes the following steps: A slurry is prepared by mixing a metal oxide semiconductor gas-sensitive material, a binder, and a dispersant, and then grinding it at least once. A mask is provided, wherein a plurality of grooves corresponding to the size of a microelectromechanical system (MEMS) sensor are provided on the mask, and a MEMS sensor is placed in each groove; A drop-coating device is provided, which is equipped with a plurality of needles corresponding to the positions of the grooves, and the slurry is drop-coated from the needles onto the surface of the microelectromechanical system sensor in the grooves and then dried.

2. The method for fabricating a microelectromechanical system semiconductor gas sensor according to claim 1, characterized in that, Each grinding process independently includes one or two of the following conditions: (1) The grinding speed is 800 rpm to 1500 rpm; (2) The grinding time is 10 min to 45 min.

3. The method for fabricating a microelectromechanical system semiconductor gas sensor according to claim 1, characterized in that, The slurry further includes a solvent, and the slurry comprises the metal oxide semiconductor gas-sensitive material, the binder, the dispersant, and the solvent in a mass ratio of (3~15):(0.5~3):(0.5~3):(80~96).

4. The method for fabricating a microelectromechanical system semiconductor gas sensor according to claim 3, characterized in that, The metal oxide semiconductor gas-sensitive material includes tin dioxide.

5. The method for fabricating a microelectromechanical system semiconductor gas sensor according to claim 3, characterized in that, The adhesive includes one or more of glass powder, epoxy resin, and polyethylene glycol.

6. The method for fabricating a microelectromechanical system semiconductor gas sensor according to claim 3, characterized in that, The dispersant includes one or more of ethyl cellulose, citric acid, and polyvinylpyrrolidone.

7. The method for fabricating a microelectromechanical system semiconductor gas sensor according to claim 3, characterized in that, The solvent includes one or more of isopropanol, methanol, terpineol, ethanol, and water.

8. The method for fabricating a microelectromechanical system semiconductor gas sensor according to any one of claims 1 to 7, characterized in that, The conditions for drop coating must meet one or more of the following conditions: (1) Dropping speed: 0.5 mm / s ~ 1.5 mm / s; (2) The drop-coating time is 100ms~200ms; (3) The dripping pressure is 0.8 kPa to 1.2 kPa.

9. The method for fabricating a microelectromechanical system semiconductor gas sensor according to any one of claims 1 to 7, characterized in that, Drying meets one or two of the following conditions: (1) The drying temperature is 50℃~80℃; (2) The drying time is 5 min to 15 min.

10. A microelectromechanical system (MEMS) semiconductor gas sensor, characterized in that, The semiconductor gas sensor for microelectromechanical systems was prepared according to any one of claims 1 to 9.

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