System and method for treating tail gas of CVD (chemical vapor deposition) equipment for depositing silicon carbide coating

Abstract

The invention discloses a system and a method for treating tail gas of CVD (Chemical Vapor Deposition) equipment for depositing a silicon carbide coating, and particularly relates to the technical field of tail gas treatment. The system comprises a high-temperature cracking module, a medium-temperature solid-phase trapping module and a low-temperature dry-type polishing module which are sequentially connected in series, and the high-temperature cracking module is used for cracking chlorosilane in tail gas into hydrogen chloride gas and solids SiO2 and Si at 800-1000 DEG C; the medium-temperature solid-phase trapping module is used for solidifying HCl into stable solid chloride by using oxide adsorption particles at 280-800 DEG C; and the low-temperature dry polishing module adsorbs residual acid gas through a solid alkali carrier at the temperature of less than or equal to 100 DEG C. According to the invention, the whole-course dry treatment of the tail gas is realized, a liquid absorption medium is not needed, the problems of condensation blockage, equipment corrosion, secondary pollution of waste liquid and the like in the prior art are fundamentally solved, and the method has the advantages of high treatment efficiency, long maintenance period, environmental friendliness, high resource utilization degree and the like.

Description

Technical Field

[0001] This invention relates to the field of exhaust gas treatment technology, specifically to an exhaust gas treatment system and method for CVD equipment with deposited silicon carbide coating, and more particularly to a staged pyrolysis curing dry treatment system and method. Background Technology

[0002] Silicon carbide (SiC) coatings are widely used in aerospace, semiconductors, thermal field structures, and protective materials due to their excellent high-temperature resistance, corrosion resistance, and high hardness. SiC coatings are typically prepared using chemical vapor deposition (CVD). At high temperatures of 1100-1500℃, trichloromethylsilane (MTS) or silicon tetrachloride (SiCl4) is used as a precursor, along with hydrogen as a reducing gas, to generate a dense SiC film through a gas-phase reaction. In addition to forming the SiC coating, this CVD process also produces a large amount of byproduct gases, mainly including hydrogen chloride (HCl), unreacted MTS or SiCl4, and small amounts of hydrogen and solid particles. These gases are complex in composition and possess strong corrosiveness and condensability. High-boiling-point substances such as SiCl4 easily condense at room temperature, forming droplets or hydrolyzing to form SiO2 powder, leading to blockage and corrosion of exhaust gas pipelines, vacuum pumps, and valve components, severely affecting the long-term stable operation of equipment. Direct emission without treatment will also cause serious environmental pollution.

[0003] Currently, the industry commonly uses wet scrubbing or alkaline absorption to treat SiC CVD tail gas. For example, patent CN1073458C proposes a CVD / CVI process tail gas treatment device that combines oil mist filtration, solid filtration, and alkaline absorption. Although this method has a simple structure, when treating high-chlorine system tail gas, SiCl4 readily hydrolyzes upon contact with water to form SiO2 gel, causing severe scaling and blockage in the absorption tower and pipelines. Simultaneously, the absorbent needs frequent replacement, generating large amounts of high-salt waste liquid, leading to secondary pollution and high operating costs.

[0004] Besides dehumidification, some technical solutions employ plasma decomposition or high-temperature combustion pyrolysis (such as patent CN112827319B) to treat exhaust gases. These methods can effectively decompose some chlorosilanes, but they are extremely energy-intensive, complex, and require stringent heat and corrosion resistance from equipment, making them difficult to promote in continuous industrial production. Furthermore, low-temperature adsorption methods (such as those using activated alumina or molecular sieves) suffer from limited adsorption capacity and susceptibility to failure, making them unsuitable for the continuous treatment of high-temperature, high-concentration chloride exhaust gases.

[0005] In summary, existing technologies generally suffer from drawbacks such as easy scaling and clogging, equipment corrosion, large wastewater discharge, high energy consumption, and frequent maintenance. Therefore, there is an urgent need in this field for a novel treatment system and method that can operate stably under dry, high-temperature conditions and achieve efficient purification and resource utilization of exhaust gas. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art and provide a CVD equipment exhaust gas treatment system and method for depositing silicon carbide coatings, so as to achieve efficient purification, solidification and resource utilization of exhaust gas under dry conditions throughout the process, fundamentally solving the problems of condensation blockage, equipment corrosion and secondary pollution.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides a CVD equipment exhaust gas treatment system for depositing silicon carbide coatings, comprising a high-temperature pyrolysis module, a medium-temperature solid phase trapping module, and a low-temperature dry polishing module connected in sequence, wherein: The high-temperature pyrolysis module is connected to an external CVD device to receive the exhaust gas input from the external CVD device and pyrolyze the chlorosilane gas in the exhaust gas to generate hydrogen chloride gas and solid silicon dioxide or silicon. The operating temperature of the high-temperature pyrolysis module is 800-1000℃. The medium-temperature solid phase capture module is filled with an oxide adsorption particle layer, which is used to capture and solidify hydrogen chloride gas in the tail gas output from the high-temperature pyrolysis module. The working temperature of the medium-temperature solid phase capture module is 280-800℃. The low-temperature dry polishing module has a honeycomb or fibrous solid alkali carrier layer inside, which is used to adsorb residual acidic gases in the exhaust gas output from the medium-temperature solid phase trapping module. The operating temperature of the low-temperature dry polishing module is no more than 100℃.

[0008] The high-temperature pyrolysis module features a cavity lined with SiC or graphite, internally connected to alternating inclined channels and a detachable solid collection chamber. Its operating temperature is between 800-1000℃. At this temperature, SiCl4, MTS, and other chlorosilanes in the exhaust gas from the external CVD equipment undergo a pyrolysis reaction, as shown in the following equation: SiCl4 + 2H2 → Si + 4HCl Or in the presence of water vapor: SiCl4 + 2H2O → SiO2 + 4HCl This process generates HCl gas and solid SiO2 or Si. The solid products fall into a solid collection chamber located at the bottom of the high-temperature pyrolysis module, thus eliminating the risk of condensation of condensable substances in the exhaust gas at the source.

[0009] The intermediate-temperature solid-phase trapping module is internally filled with a layer of oxide adsorption particles with high specific surface area, such as Y₂O₃, MgO, CaO, or ZrO₂. The particle size is 1-5 mm, and the thickness of the oxide adsorption particle layer is 30-80 mm. The operating temperature is between 280-800℃. At this temperature, HCl gas undergoes a solid-phase reaction with the oxide particles, as shown in the following reaction formula: Y₂O₃ + 6HCl → 2YCl₃ + 3H₂O MgO + 2HCl → MgCl2 + H2O CaO + 2HCl → CaCl2 + H2O ZrO2 + 4HCl → ZrCl4 + 2H2O This process generates stable solid chloride, thereby achieving the solidification and capture of acidic gas HCl. No liquid waste is generated during this process. The medium-temperature solid phase capture module is connected to a drawer-type replaceable bed, on which the oxide adsorption particle layer is placed for easy maintenance.

[0010] The low-temperature dry polishing module has a honeycomb or fibrous solid alkali carrier layer inside, and the surface of the carrier is coated with alkaline substances such as NaOH, Ca(OH)2 or MgO. The operating temperature does not exceed 100℃. Under these conditions, the trace amounts of acidic gases such as HCl and Cl2 remaining in the exhaust gas of the medium-temperature solid phase trapping module are effectively adsorbed and neutralized. The neutralization reaction formula is as follows: NaOH + HCl → NaCl + H2O This section only lists the neutralization reaction formula between alkaline substance NaOH and acidic gas HCl. Based on the low-temperature dry polishing module, the exhaust gas is purified. After purification, the HCl concentration in the exhaust gas can be reduced to below 5mg / m³, and the pH is close to neutral, meeting the clean emission requirements. The gas flow resistance inside the low-temperature dry polishing module is less than 200Pa, and the solid alkali carrier layer adopts a honeycomb structure for easy replacement.

[0011] The system also includes a control system, a temperature control unit, and monitoring sensors. The control system is connected to the temperature control unit and the monitoring sensors. The monitoring sensors include a pressure sensor, a flow sensor, and a temperature sensor respectively installed in the high-temperature pyrolysis module, the medium-temperature solid phase trapping module, and the low-temperature dry polishing module. The temperature control unit includes a resistance heating control unit or a graphite heating control unit installed in the high-temperature pyrolysis module, a jacket heating control unit installed in the medium-temperature solid phase trapping module, and a micro-heating control unit installed in the low-temperature dry polishing module. The pressure sensor and the flow sensor monitor the pressure and flow rate in the high-temperature pyrolysis module, the medium-temperature solid phase trapping module, and the low-temperature dry polishing module, respectively, and transmit the monitored information to the control system. The control system uses the received information to achieve full-process automatic control of the high-temperature pyrolysis module, the medium-temperature solid phase trapping module, and the low-temperature dry polishing module.

[0012] In some embodiments, a gas bypass pipeline is also included, which is connected in parallel with the high-temperature pyrolysis module, the medium-temperature solid phase trapping module, and the low-temperature dry polishing module. Based on this gas bypass pipeline, online maintenance of the high-temperature pyrolysis module, the medium-temperature solid phase trapping module, and the low-temperature dry polishing module can be performed without shutting down the system.

[0013] Secondly, the present invention also provides a method for treating exhaust gas from a CVD equipment with a deposited silicon carbide coating. This method, based on the aforementioned CVD equipment exhaust gas treatment system with a deposited silicon carbide coating, treats the exhaust gas from an external CVD equipment, specifically including the following steps: S100: High-temperature chlorine-containing tail gas from the SiC CVD reactor is introduced into the high-temperature pyrolysis module and pyrolysis reaction is carried out at 800-1000℃ to decompose SiCl4 and MTS in the tail gas into solid SiO2 or Si and HCl gas. S200: The gas after pyrolysis in step S100 is introduced into the medium-temperature solid phase trapping module, and at 280-800℃, the HCl gas reacts with the oxide adsorbed particles to generate solid chloride. S300. The exhaust gas after step S200 is introduced into a low-temperature dry polishing module. Under conditions of ≤100℃, the exhaust gas passes through a solid alkaline carrier layer to adsorb residual acidic gases. S400: The exhaust gas purified by step S300 is directly discharged into the vacuum system or the exhaust port.

[0014] Compared with the prior art, the present invention has the following beneficial technical effects: (1) Completely eliminate condensation blockage: The easily condensable chlorosilane is converted into a solid by high-temperature pyrolysis, which avoids the problem of condensation and scale buildup in pipelines and equipment from the source.

[0015] (2) Dry process with no waste liquid: Solid phase capture and adsorption are used. The entire treatment process does not require water or alkali solution and does not generate any waste liquid, thus eliminating secondary pollution.

[0016] (3) High efficiency purification and resource utilization: SiCl4 conversion rate exceeds 95%, and HCl removal rate is greater than 99%. The SiO2 powder and solid chloride produced by pyrolysis can be collected and utilized as resources.

[0017] (4) Long equipment life and easy maintenance: Modular and replaceable design (such as drawer-type collection bins and bed layers), combined with bypass system, realizes non-stop maintenance, maintenance cycle exceeds 200 hours, and greatly reduces operating costs.

[0018] (5) Low energy consumption and high stability: Compared with plasma methods, the present invention adopts a gradient temperature zone design, which makes reasonable energy utilization, and the system operates stably and reliably, making it suitable for industrial continuous production. Attached Figure Description

[0019] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0020] Figure 1 This is a schematic diagram of the exhaust gas treatment system of a CVD equipment for depositing silicon carbide coating according to the present invention; Figure 2 for Figure 1 AA section view; Figure 3 A flowchart of a CVD equipment exhaust gas treatment method for depositing silicon carbide coatings according to the present invention.

[0021] In the figure: 1. High-temperature pyrolysis module, 11. Inclined chute, 12. Solid collection chamber, 2. Medium-temperature solid phase trapping module, 21. Drawer-type replaceable bed, 3. Low-temperature dry polishing module, 31. Solid alkali support layer, 41. Resistance heating control unit or graphite heating control unit, 42. Jacket heating control unit, 43. Micro heating control unit, 5. CVD equipment. Detailed Implementation

[0022] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way.

[0023] like Figure 1 , Figure 2 As shown, Figure 1The arrows in the diagram indicate the direction of exhaust gas transport. This invention provides an exhaust gas treatment system for a CVD equipment with deposited silicon carbide coatings, comprising a high-temperature pyrolysis module 1, a medium-temperature solid phase trapping module 2, and a low-temperature dry polishing module 3 connected in sequence, wherein: The high-temperature pyrolysis module 1 is connected to the external CVD equipment 5 to receive the exhaust gas input from the external CVD equipment 5 and pyrolyze the chlorosilane gas in the exhaust gas to generate hydrogen chloride gas and solid silicon dioxide or silicon. The operating temperature of the high-temperature pyrolysis module 1 is 800-1000℃. The medium-temperature solid phase capture module 2 is filled with an oxide adsorption particle layer, which is used to capture and solidify hydrogen chloride gas in the tail gas output from the high-temperature pyrolysis module 1. The working temperature of the medium-temperature solid phase capture module 2 is 280-800℃. The low-temperature dry polishing module 3 is equipped with a honeycomb or fibrous solid alkali carrier layer 31, which is used to adsorb residual acidic gases in the exhaust gas output from the medium-temperature solid phase trapping module 2. The operating temperature of the low-temperature dry polishing module 3 is not greater than 100℃.

[0024] In the above embodiment, the high-temperature pyrolysis module 1 is connected with an alternately arranged inclined channel 11 to extend the residence time of the exhaust gas in the high-temperature pyrolysis module 1, thereby increasing the pyrolysis time of the exhaust gas in the high-temperature pyrolysis module 1, ensuring that the chlorosilane gas in the exhaust gas can be completely converted into hydrogen chloride gas and solid silicon dioxide or silicon.

[0025] In the above embodiment, the bottom of the high-temperature pyrolysis module 1 is detachably connected to a solid collection chamber 12 for collecting the solid silica or silicon generated after pyrolysis. The solid collection chamber 12 is designed as a drawer. When the solid silica or silicon collected in the solid collection chamber 12 needs to be cleaned, the drawer design greatly facilitates the operation of the operator, thereby reducing the labor intensity of the operator and improving the work efficiency of the operator.

[0026] In the above embodiment, the medium-temperature solid phase trapping module 2 is connected to a drawer-type replaceable bed 21, and the oxide adsorption particle layer is disposed on the drawer-type replaceable bed 21. The oxide adsorption particles in the oxide adsorption particle layer are Y2O3, MgO, CaO or ZrO2 particles with a particle size range of 1-5mm, and the thickness of the oxide adsorption particle layer is 30-80mm. It should be noted that when selecting oxide adsorption particles, it should be considered that the substance generated by the oxide particles and hydrogen chloride gas remains stable in a solid state at the current operating temperature of the medium-temperature solid-phase trapping module 2. For example, zirconium chloride generated by ZrO2 and HCl will sublimate at a temperature of 331℃. Therefore, when ZrO2 is selected as the oxide particle in the medium-temperature solid-phase trapping module 2, the operating temperature of the medium-temperature solid-phase trapping module 2 should be lower than 330℃. Similarly, calcium chloride generated by CaO and HCl will dissolve at a temperature of 772℃. Therefore, when CaO is selected as the oxide particle in the medium-temperature solid-phase trapping module 2, the operating temperature of the medium-temperature solid-phase trapping module 2 should be lower than 770℃, thereby ensuring that the generated calcium chloride is a stable solid state.

[0027] In the above embodiments, by placing the oxide adsorption particle layer on the drawer-type replaceable bed 21, it is convenient to quickly replace the oxide adsorption particles when their performance deteriorates or they fail.

[0028] In the above embodiments, the honeycomb solid alkali carrier layer 31 is a honeycomb ceramic structure with NaOH, Ca(OH)2 or MgO coated on the surface. By setting the solid alkali carrier layer 31 as a honeycomb ceramic structure, its gas flow resistance is lower than 200 Pa, which facilitates its adsorption and neutralization of residual trace amounts of acidic gases such as HCl and Cl2 in the tail gas.

[0029] In this embodiment, the high-temperature cracking of chlorosilanes, the solid-phase capture of hydrogen chloride, and the dry purification of acidic gases in the exhaust gas are achieved through the high-temperature cracking module 1, the medium-temperature solid-phase capture module 2, and the low-temperature dry polishing module 3. This invention adopts a dry continuous treatment method without condensation, blockage, or waste liquid discharge, which fundamentally eliminates the inherent blockage and secondary pollution problems of wet systems, reduces equipment corrosion, extends the service life of components, and achieves efficient purification and resource utilization of exhaust gas.

[0030] The above embodiments also include a control system (not shown in the figure), a temperature control unit (not shown in the figure), and monitoring sensors (not shown in the figure). The control system is connected to the temperature control unit and the monitoring sensors respectively. The monitoring sensors include a pressure sensor, a flow sensor, and a temperature sensor respectively installed in the high-temperature pyrolysis module 1, the medium-temperature solid phase trapping module 2, and the low-temperature dry polishing module 3. The temperature control unit includes a resistance heating control unit or a graphite heating control unit 41 installed in the high-temperature pyrolysis module, a jacket heating control unit 42 installed in the medium-temperature solid phase trapping module, and a micro-heating control unit 43 installed in the low-temperature dry polishing module (or using natural cooling). The pressure sensor and the flow sensor respectively monitor the pressure and flow in the high-temperature pyrolysis module 1, the medium-temperature solid phase trapping module 2, and the low-temperature dry polishing module 3 and transmit the monitored information to the control system. The control system realizes full-process automatic control of the high-temperature pyrolysis module 1, the medium-temperature solid phase trapping module 2, and the low-temperature dry polishing module 3 through the received information.

[0031] In some embodiments, a gas bypass pipeline (not shown in the figure) is also included, which is connected in parallel with the high-temperature pyrolysis module 1, the medium-temperature solid phase trapping module 2, and the low-temperature dry polishing module 3. When maintenance is required on one or more of the high-temperature pyrolysis module 1, the medium-temperature solid phase trapping module 2, and the low-temperature dry polishing module 3, the exhaust gas output from the external CVD equipment 5 can be temporarily transported through this gas bypass pipeline, realizing maintenance of the exhaust gas treatment system without shutting down the system.

[0032] In some implementations, a redundant exhaust gas treatment system can be set up. When one of the exhaust gas treatment systems fails or needs maintenance, the redundant exhaust gas treatment system can be used to treat the exhaust gas output by the external CVD equipment 5, thereby ensuring the normal treatment of the exhaust gas output by the external CVD equipment 5.

[0033] like Figure 2 As shown, the present invention also provides a method for treating exhaust gas from a CVD equipment with a deposited silicon carbide coating. This method treats exhaust gas from an external CVD equipment based on the aforementioned CVD equipment exhaust gas treatment system with a deposited silicon carbide coating. The method includes the following steps: S100. The exhaust gas from the external CVD equipment 5 is introduced into the high-temperature pyrolysis module 1 and pyrolysis reaction is carried out at a temperature of 800-1000℃ so that SiCl4 and / or MTS in the exhaust gas are decomposed to generate HCl gas and solid SiO2 or Si. S200. The gas after cracking in step 1 is introduced into the medium-temperature solid phase trapping module 2, and at 280-800℃, the HCl gas reacts with the oxide adsorbed particles to generate solid chloride. S300. The exhaust gas after step 2 is introduced into the low-temperature dry polishing module 3. Under the condition of ≤100℃, the exhaust gas passes through the solid alkaline carrier layer 31 to adsorb the residual acidic gas. S400: The exhaust gas purified in step 3 is directly discharged into the vacuum system or the exhaust port.

[0034] As can be seen from the above description of the exhaust gas treatment system, the specific method for treating the exhaust gas output from the CVD equipment 5 based on this exhaust gas treatment system has the same beneficial technical effect, and will not be repeated here.

[0035] To further illustrate the working principle and technical effects of the present invention, the following examples are provided for comparison. In the examples below, CaO is selected as the oxide particle in the medium-temperature solid phase trapping module 2. Other oxide particles can also be selected. For different oxide particles, the working temperature in the medium-temperature solid phase trapping module 2 needs to be adjusted according to the actual situation so that the generated substance remains stable in a solid state.

[0036] Example 1 1) The exhaust gas from the external CVD equipment 5 is introduced into the high-temperature pyrolysis module 1 and pyrolysis reaction is carried out at a temperature of 1000℃ so that SiCl4 and / or MTS in the exhaust gas decompose to generate HCl gas and solid SiO2 or Si. 2) The gas after pyrolysis in step 1) is introduced into the medium-temperature solid phase trapping module 2, and at 280°C, the HCl gas reacts with the CaO adsorbed particles to generate solid calcium chloride. 3) The exhaust gas after step 2) is introduced into the low-temperature dry polishing module 3. Under the condition of 100°C, the exhaust gas passes through the solid alkaline carrier layer 31 to adsorb the residual acidic gas. 4) The exhaust gas purified in step 3) is directly discharged into the vacuum system or exhaust port.

[0037] Example 2 1) The exhaust gas from the external CVD equipment 5 is introduced into the high-temperature pyrolysis module 1 and pyrolysis reaction is carried out at a temperature of 900℃ so that SiCl4 and / or MTS in the exhaust gas decompose to generate HCl gas and solid SiO2 or Si. 2) The gas after pyrolysis in step 1) is introduced into the medium-temperature solid phase trapping module 2, and at 400℃, the HCl gas reacts with the CaO adsorbed particles to generate solid calcium chloride. 3) The exhaust gas after step 2) is introduced into the low-temperature dry polishing module 3. Under the condition of 80°C, the exhaust gas passes through the solid alkaline carrier layer 31 to adsorb the residual acidic gas. 4) The exhaust gas purified in step 3) is directly discharged into the vacuum system or exhaust port.

[0038] Example 3 1) The exhaust gas from the external CVD equipment 5 is introduced into the high-temperature pyrolysis module 1 and pyrolysis reaction is carried out at a temperature of 800℃ so that SiCl4 and / or MTS in the exhaust gas decompose to generate HCl gas and solid SiO2 or Si. 2) The gas after pyrolysis in step 1) is introduced into the medium-temperature solid phase trapping module 2, and at 770°C, the HCl gas reacts with the CaO adsorbed particles to generate solid calcium chloride. 3) The exhaust gas after step 2) is introduced into the low-temperature dry polishing module 3. Under the condition of 60°C, the exhaust gas passes through the solid alkaline carrier layer 31 to adsorb the residual acidic gas. 4) The exhaust gas purified in step 3) is directly discharged into the vacuum system or exhaust port.

[0039] The gases emitted in step 4) of Examples 1-3 were sampled and analyzed, and the analysis results are shown in Table 1.

[0040] Table 1 Performance test results of Examples 1-2 and Comparative Examples 1-4 Chlorosilane gas content (%) Hydrogen chloride gas content (%) Chlorine content (%) Example 1 2.6 0.8 0.01 Example 2 2.1 0.6 0.02 Example 3 1.7 0.9 0.01 As can be seen from Table 1, the content of chlorosilane gas in the exhaust gas after treatment by the exhaust gas treatment system in Examples 1-3 is less than 3%, the content of hydrogen chloride gas is less than 1%, and the content of chlorine gas is less than 0.02%. Therefore, after the exhaust gas output from the external CVD equipment 5 is treated by the exhaust gas treatment system provided by this invention, the SiCl4 conversion rate in the exhaust gas exceeds 97%, the HCl removal rate is greater than 99%, and the chlorine removal rate is as high as 99.98%.

[0041] In summary, the exhaust gas treatment system and method of the present invention can effectively remove chlorosilane gas and hydrogen chloride gas from the exhaust gas output from the external CVD equipment 5. Moreover, the CVD equipment exhaust gas treatment system and method for depositing silicon carbide coating provided by the present invention adopts a dry continuous treatment method with no condensation, no clogging, and no waste liquid discharge, which fundamentally eliminates the inherent clogging and secondary pollution problems of wet systems, reduces equipment corrosion, extends the service life of components, and achieves efficient purification and resource utilization of exhaust gas.

[0042] The foregoing provides a detailed description of a CVD equipment exhaust gas treatment system and method for depositing silicon carbide coatings, as provided in this application. Specific examples have been used to illustrate the principles and implementation methods of this application; the descriptions of these embodiments are merely for the purpose of helping to understand the core ideas of this application. It should be noted that those skilled in the art can make various improvements and modifications to this application without departing from its principles, and these improvements and modifications also fall within the protection scope of the claims of this application.

Claims

1. A CVD equipment exhaust gas treatment system for depositing silicon carbide coatings, characterized in that, It includes a high-temperature pyrolysis module (1), a medium-temperature solid phase trapping module (2), and a low-temperature dry polishing module (3) connected in sequence, wherein: The high-temperature pyrolysis module (1) is connected to an external CVD device to receive the exhaust gas input from the external CVD device and pyrolyze the chlorosilane gas in the exhaust gas to generate hydrogen chloride gas and solid silicon dioxide or silicon. The working temperature of the high-temperature pyrolysis module (1) is 800-1000℃. The medium-temperature solid phase capture module (2) is filled with an oxide adsorption particle layer, which is used to capture and solidify hydrogen chloride gas in the tail gas output from the high-temperature pyrolysis module (1). The working temperature of the medium-temperature solid phase capture module (2) is 280-800℃. The low-temperature dry polishing module (3) is provided with a honeycomb or fibrous solid alkali carrier layer (31) for adsorbing residual acidic gases in the exhaust gas output from the medium-temperature solid phase trapping module (2). The working temperature of the low-temperature dry polishing module (3) is not greater than 100℃.

2. The CVD equipment exhaust gas treatment system for depositing silicon carbide coatings according to claim 1, characterized in that, The high-temperature pyrolysis module (1) is connected to an alternating inclined channel (11) to extend the residence time of the exhaust gas in the high-temperature pyrolysis module (1).

3. The CVD equipment exhaust gas treatment system for depositing silicon carbide coating according to claim 2, characterized in that, The high-temperature pyrolysis module (1) has a detachable solid collection chamber (12) at the bottom for collecting solid silicon dioxide or silicon generated after pyrolysis.

4. The CVD equipment exhaust gas treatment system for depositing silicon carbide coatings according to claim 1, characterized in that, The medium-temperature solid phase trapping module (2) is internally connected to a drawer-type replaceable bed (21), and the oxide adsorption particle layer is set on the drawer-type replaceable bed (21).

5. The CVD equipment exhaust gas treatment system for depositing silicon carbide coating according to claim 4, characterized in that, The oxide adsorbent particles in the oxide adsorbent particle layer are Y2O3, MgO, CaO or ZrO2 particles with a particle size range of 1-5 mm, and the thickness of the oxide adsorbent particle layer is 30-80 mm.

6. The CVD equipment exhaust gas treatment system for depositing silicon carbide coating according to claim 4, characterized in that, The honeycomb-shaped solid alkali carrier layer (31) is a honeycomb ceramic structure with NaOH, Ca(OH)2 or MgO coated on the surface, and its gas flow resistance is less than 200 Pa.

7. The CVD equipment exhaust gas treatment system for depositing silicon carbide coatings according to claim 6, characterized in that, It also includes a control system. The high-temperature pyrolysis module (1), the medium-temperature solid phase trapping module (2) and the low-temperature dry polishing module (3) are all equipped with temperature control units and monitoring sensors connected to the control system.

8. The CVD equipment exhaust gas treatment system for depositing silicon carbide coatings according to claim 7, characterized in that, The high-temperature pyrolysis module (1) is heated by resistance wire heating or graphite heating body heating; the medium-temperature solid phase trapping module (2) is heated by jacket heating; and the low-temperature dry polishing module (3) is controlled by natural cooling or micro-heating.

9. The CVD equipment exhaust gas treatment system for depositing silicon carbide coating according to claim 7, characterized in that, It also includes a gas bypass pipeline that is connected in parallel with the high-temperature pyrolysis module (1), the medium-temperature solid phase trapping module (2) and the low-temperature dry polishing module (3).

10. A method for treating exhaust gas from a CVD equipment with deposited silicon carbide coating, characterized in that, The CVD equipment exhaust gas treatment system based on the silicon carbide coating as described in any one of claims 1-9 treats the exhaust gas from an external CVD equipment, the method comprising the following steps: S100. The exhaust gas from the external CVD equipment is introduced into the high-temperature pyrolysis module (1) and pyrolysis reaction is carried out at a temperature of 800-1000℃ so that SiCl4 and / or MTS in the exhaust gas are decomposed to generate HCl gas and solid SiO2 or Si. S200, The gas after cracking in step S100 is introduced into the medium-temperature solid phase trapping module (2), and at 280-800℃, the HCl gas reacts with the oxide adsorbed particles to generate solid chloride. S300, The exhaust gas after step S200 is introduced into the low-temperature dry polishing module (3), and under the condition of ≤100℃, the exhaust gas passes through the solid alkali carrier layer (31) to adsorb the residual acidic gas. S400: The exhaust gas purified by step S300 is directly discharged into the vacuum system or the exhaust port.

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