Method and device for cleaning intake pipe by low-temperature plasma

Abstract

The application provides a method and a device for cleaning an air inlet pipe by low-temperature plasma, and relates to the field of solar cell manufacturing. The method comprises the following steps: performing ultraviolet light catalysis pretreatment on an air inlet pipe to be cleaned in a vacuum environment; after the pretreatment, a first cleaning is performed on the air inlet pipe by rotating electrode pulse plasma by inputting a first gas; and a second cleaning is performed on the air inlet pipe by inputting a second gas. The first gas comprises Ar and H2, and the second gas comprises Ar, H2 and N2. The whole cleaning process of the technical scheme does not need to add mixed acid liquid, thereby reducing the production cost and the cost of treating waste acid.

Description

Technical Field

[0001] This application relates to the field of solar cell manufacturing, and in particular to a method and apparatus for cleaning an air inlet pipe using low-temperature plasma synergistic cleaning. Background Technology

[0002] In the TOPCon battery LPCVD process, the metal inlet pipe is used to transport reaction gases such as silane and phosphine. After long-term operation, the inner wall of the inlet pipe contains: 1) incompletely decomposed SiH4 deposits on the pipe wall, forming a dense silicon carbide layer, Polysilicon coke; 2) metal oxides such as Fe3O4 and Cr2O3 are generated by the reaction of metal with oxygen at high temperatures; 3) residual chloride salts such as NH4Cl are crystallized by the reaction of PH3 and HCl.

[0003] Existing cleaning methods often employ a mixture of HF and HNO3 for immersion. However, on the one hand, HF reacts with metals to form soluble fluorides, resulting in thinner pipe walls and a shorter lifespan. On the other hand, the residues formed on the inner wall of the intake pipe are stubborn, and the silicon carbide layer requires high-temperature (>1000℃) sintering for removal, which is energy-intensive and can easily damage the pipe structure. In addition, the cost of treating fluoride-containing wastewater is high and does not meet the requirements of green manufacturing.

[0004] Therefore, how to solve the problems of metal corrosion and incomplete removal of residues caused by traditional pickling, and thus improve cleaning efficiency and optimize energy consumption, has become the key to improving product quality and reducing production costs in production. Summary of the Invention

[0005] The purpose of this application is to provide a method and apparatus for cleaning an air inlet pipe using low-temperature plasma synergistic cleaning, in order to solve the above-mentioned problems.

[0006] To achieve the above objectives, this application adopts the following technical solution:

[0007] This application provides a method for low-temperature plasma-assisted cleaning of an air inlet pipe, comprising:

[0008] The intake pipe to be cleaned is pretreated with ultraviolet photocatalysis in a vacuum environment; after the pretreatment, a first gas is introduced and a rotating electrode pulsed plasma is used for the first cleaning.

[0009] The intake pipe, which has undergone the first cleaning, is then purged with a second gas for a second cleaning.

[0010] The first gas includes Ar and H2;

[0011] The second gas includes Ar, H2 and N2.

[0012] Optionally, the vacuum environment is a gradient vacuum environment, wherein the initial vacuum level in the gradient vacuum environment is 0.5 × 10⁻⁶.-3 -2×10 -3 Torr, the final vacuum level is 1×10 -6 -2×10 -6 Torr.

[0013] Optionally, after the vacuum level in the intake pipe reaches the initial vacuum level, the ultraviolet photocatalytic pretreatment is performed.

[0014] Optionally, the conditions for the ultraviolet photocatalytic pretreatment are as follows: the reaction gas includes O2 or gaseous H2O; the ultraviolet light source wavelength is 254 nm, and the intensity is not less than 50 mW / cm². 2 The irradiation time is 30-60 minutes.

[0015] Optionally, the volume ratio of Ar to H2 in the first gas is 4-5:1.

[0016] Optionally, the volume ratio of Ar, H2 and N2 in the second gas is 4-5:2-3:1-2.

[0017] Optionally, the conditions for the first cleaning are: a rotational speed of 5-20 rpm for the rotating electrode structure; a pulse frequency of 10-50 kHz; and a power density of 5-10 W / cm². 2 Processing time is 10-20 minutes.

[0018] Optionally, the total flow rate of the second gas is 50-100 sccm, and the pressure is 0.5 × 10⁻⁶. -4 -2×10 -4 Torr, the time is 25-35 minutes.

[0019] Optionally, the collaborative cleaning method further includes post-processing, the post-processing process including: introducing O3 into the air intake pipe, forming a SiO2 passivation layer on the inner wall of the air intake pipe, and monitoring the surface elemental composition inside the air intake pipe.

[0020] Optionally, the post-treatment conditions are: O3 concentration of 100-200 ppm, reaction temperature of 50-80℃, and treatment time of 20-40 minutes.

[0021] This application also provides an apparatus for cryogenic plasma co-cleaning an air inlet pipe, and a method for performing the cryogenic plasma co-cleaning of the air inlet pipe. The apparatus for cryogenic plasma co-cleaning of the air inlet pipe includes a modular cavity system and an intelligent sensing system.

[0022] The modular cavity comprises independent components:

[0023] Pretreatment chamber: used to pre-decompose organic matter and reduce the subsequent cleaning load;

[0024] Plasma cavity: used to improve the uniformity of plasma distribution;

[0025] Post-treatment chamber: used to form a surface passivation protective layer in the intake pipe;

[0026] The pretreatment chamber is equipped with an ultraviolet photocatalytic module; the plasma chamber adopts a rotating electrode structure; the posttreatment chamber includes an ozone generator and a humidity control device.

[0027] The intelligent sensing system includes:

[0028] LIBS online detection module: used for real-time analysis of contaminant composition on pipe walls and dynamic adjustment of cleaning parameters;

[0029] Pressure-flow closed-loop control system: Used in closed-loop control systems to ensure process stability.

[0030] Compared with the prior art, the beneficial effects of this application include:

[0031] The cleaning method provided in this application decomposes organic matter through photocatalytic reaction, reducing the plasma cleaning load and enhancing the pollutant dissociation efficiency through pressure changes. A rotating electrode structure is employed during the cleaning process to improve plasma distribution uniformity. Plasma bombardment causes the surface layer of pollutants to peel off. An Ar / H2 / N2 mixed gas is used, leveraging the reducing properties of H2 synergistically with the physical bombardment effect of N2 to resolve the problem of residual metal oxides. Furthermore, the entire cleaning process does not require the addition of mixed acid, reducing production costs and the cost of waste acid treatment. Attached Figure Description

[0032] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation on the scope of this application.

[0033] Figure 1 The LPCVD silicon tube before cleaning in Example 1;

[0034] Figure 2 The LPCVD silicon tube after cleaning in Example 1;

[0035] Figure 3 The image shows an LPCVD silicon tube cleaned using a conventional method in Comparative Example 3. Detailed Implementation

[0036] As used in this article:

[0037] "Prepared from" is synonymous with "comprising". The terms "comprising", "including", "having", "containing", or any other variations thereof as used herein are intended to cover non-exclusive inclusion. For example, a composition, step, method, article, or apparatus that includes the listed elements is not necessarily limited to those elements, but may include other elements not expressly listed or elements inherent to such composition, step, method, article, or apparatus.

[0038] The conjunction "composed of..." excludes any unspecified elements, steps, or components. If used in a claim, this phrase makes the claim closed, excluding materials other than those described, except for associated conventional impurities. When the phrase "composed of..." appears in a clause of the body of a claim rather than immediately following it, it limits only the elements described in that clause; other elements are not excluded from the claim as a whole.

[0039] When a quantity, concentration, or other value or parameter is expressed as a range, a preferred range, or a range defined by a series of upper and lower preferred values, this should be understood as specifically disclosing all ranges formed by any pair of any upper or preferred value with any lower or preferred value, regardless of whether the range is disclosed individually. For example, when the range “1–5” is disclosed, the described range should be interpreted as including ranges “1–4”, “1–3”, “1–2”, “1–2 and 4–5”, “1–3 and 5”, etc. When numerical ranges are described herein, unless otherwise stated, the range is intended to include its endpoints and all integers and fractions within that range.

[0040] In these embodiments, unless otherwise specified, the portions and percentages are all by weight.

[0041] "Parts by mass" refers to the basic unit of measurement that expresses the mass ratio of multiple components. One part can represent any unit mass, such as 1g or 2.689g. If we say that component A has "a" parts by mass and component B has "b" parts by mass, it means the ratio of the mass of component A to the mass of component B is a:b. Alternatively, it can mean that the mass of component A is aK and the mass of component B is bK (K is any number representing a multiplier). It is important to understand that, unlike the number of parts by mass, the sum of the mass parts of all components is not limited to 100 parts.

[0042] "And / or" is used to indicate that one or both of the described situations may occur, for example, A and / or B includes (A and B) and (A or B).

[0043] To better explain the technical solution provided in this application, the technical solution will be described in its entirety before proceeding with specific implementation methods.

[0044] In a first aspect, this application provides a method for cryogenic plasma-assisted cleaning of an air inlet pipe, the method comprising:

[0045] The intake pipe to be cleaned is pretreated with ultraviolet photocatalysis in a vacuum environment; after the pretreatment, a first gas is introduced and a rotating electrode pulsed plasma is used for the first cleaning.

[0046] The intake pipe, which has undergone the first cleaning, is then purged with a second gas for a second cleaning.

[0047] The first gas includes Ar and H2;

[0048] The second gas includes Ar, H2 and N2.

[0049] Analysis of the contaminant composition revealed that the silicon carbide layer requires a synergistic effect of physical stripping and chemical reduction, metal oxides require hydrogen reduction, and chlorides require nitrogen participation in the chemical reaction. Based on this, a method of surface activation through ultraviolet photocatalytic pretreatment, combined with two-stage plasma cleaning, is proposed, utilizing different gas combinations to achieve stepwise removal. Specifically, in the ultraviolet photocatalytic pretreatment stage, reactive oxygen species decompose organic matter and oxidize the metal surface, forming a transition layer that is easily processed later. In the first cleaning stage, argon ions in the pulsed plasma generated by the rotating electrode disrupt the silicon carbide layer structure through kinetic energy impact, while hydrogen radicals reduce high-valence metal oxides to elemental or low-valence compounds. In the second cleaning stage, nitrogen radicals undergo a displacement reaction with chlorides, generating gaseous products that detach from the tube wall.

[0050] Through the above technical solutions, this application avoids the corrosion of metal pipes by acid and extends the service life of the intake pipe; through the phased gas combination and plasma synergy, the silicon carbide layer, metal oxide and chloride crystals are completely removed; the use of low temperature treatment reduces energy consumption, and there is no need to treat fluoride-containing wastewater, which meets the requirements of green manufacturing.

[0051] In one optional embodiment, the vacuum environment is a gradient vacuum environment, wherein the initial vacuum level in the gradient vacuum environment is 0.5 × 10⁻⁶. -3 -2×10 -3 Torr, the final vacuum level is 1×10 -6 -2×10 -6 Torr.

[0052] A gradient vacuum environment refers to a pressure environment in which the vacuum level is continuously adjusted in stages during the cleaning process. This can be achieved through a multi-stage vacuum pump system combined with pressure sensors, gradually reducing the pressure to meet the vacuum requirements at different stages. In the UV photocatalytic pretreatment stage, the initial vacuum level is 1×10⁻⁶. -3Torr allows the reactant gases to be evenly distributed on the inner wall of the inlet pipe, promoting sufficient contact between the photocatalytic reactant gases and the residues. As the vacuum level is gradually reduced to 1×10⁻⁶, -6 Torr increases the degree of freedom of gas molecules and enhances the kinetic energy of active particles in the plasma, thereby improving the bombardment efficiency against stubborn deposits. Continuous variation in vacuum avoids stress concentration in the pipeline caused by sudden pressure changes under a single vacuum level. Simultaneously, staged venting effectively removes volatile byproducts generated during the cleaning process, preventing secondary deposition. In this way, this application solves the problems of incomplete residue removal and pipeline damage caused by improper vacuum control in traditional cleaning methods, achieving staged cleaning from surface loosening to deep peeling of residues.

[0053] In an optional embodiment, the ultraviolet photocatalytic pretreatment is performed after the vacuum level in the intake pipe reaches the initial vacuum level.

[0054] When the vacuum level reaches the initial set value, the pressure sensor triggers the ultraviolet light source to start. At this time, the reactant gas diffuses uniformly to the tube wall surface in the low-pressure environment. The ultraviolet photon energy is absorbed by O2 or H2O molecules, generating hydroxyl radicals and superoxide radicals. Since the vacuum level is stable, the contact area between the radicals and the deposits on the tube wall increases significantly. The Si-Si bonds in the silicon carbide layer break under oxidation, and the metal oxide particles are gradually peeled off. The stability of the vacuum level during the pretreatment process ensures the controllability of the radical concentration and prevents discontinuity of the reaction interface due to pressure fluctuations. In this way, the pretreatment process can always be carried out under an optimized low-pressure environment, enhancing the directional migration ability of active radicals, thereby improving the oxidative decomposition efficiency of the silicon carbide layer and metal oxides.

[0055] In an optional embodiment, the conditions for the ultraviolet photocatalytic pretreatment are as follows: the reaction gas includes O2 or gaseous H2O; the ultraviolet light source wavelength is 254 nm, and the intensity is not less than 50 mW / cm². 2 The irradiation time is 30-60 minutes.

[0056] Optionally, the intensity of the ultraviolet light source can be 50 mW / cm². 2 60mW / cm 2 70mW / cm 2 80mW / cm 2 90mW / cm 2 100mW / cm 2 Or not less than 50mW / cm 2 Any value; the UV irradiation and treatment time can be 30 min, 35 min, 40 min, 45 min, 50 min, 55 min, 60 min, or any value between 30 and 60 min.

[0057] Specifically, under vacuum, oxygen and water vapor undergo photolysis under 254 nm ultraviolet light irradiation, generating hydroxyl radicals and reactive oxygen species. The hydroxyl radicals possess strong oxidizing properties, capable of oxidizing the organic components in the silicon carbide layer into carbon dioxide and water, while simultaneously decomposing the metal-oxygen bonds in the metal oxides. The reactive oxygen species further react with chloride crystals to generate volatile chloride oxides. The ultraviolet intensity is not less than 50 mW / cm². 2 Ensure that sufficient electron-hole pairs are generated on the surface of the photocatalyst to maintain the continuous progress of the oxidation reaction.

[0058] In one optional embodiment, the volume ratio of Ar to H2 in the first gas is 4-5:1.

[0059] Optionally, the volume ratio of Ar to H2 in the first gas can be 4:1, 4.1:1, 4.2:1, 4.3:1, 4.4:1, 4.5:1, 4.6:1, 4.7:1, 4.8:1, 4.9:1, 5:1, or any value between 4 and 5:1.

[0060] In one optional embodiment, the volume ratio of Ar, H2, and N2 in the second gas is 4-5:2-3:1-2.

[0061] Optionally, the volume ratio of Ar, H2 and N2 in the second gas can be 4:2:1, 4:3:1, 4:2:2, 4:3:2, 5:2:1, 5:3:2, or any value between 4-5:2-3:1-2.

[0062] In this way, during the first cleaning stage, when the volume ratio of Ar to H2 is 4:1, the high-energy particle bombardment of Ar and the reduction reaction of H2 create a synergistic effect. At this ratio, the proportion of Ar ensures that the plasma energy density remains within a stable range, and the concentration of H2 is controlled at a critical value that effectively decomposes metal oxides such as Fe3O4 while avoiding intergranular corrosion of the pipes caused by excessive hydrogen atom penetration. In the second cleaning stage, when the volume ratio of Ar, H2, and N2 is 5:3:2, the introduction of N2 promotes the generation of active intermediates such as NH3, removing NH4Cl residues through chemisorption. At the same time, the proportion of Ar maintains the plasma ionization efficiency, and the ratio of H2 to N2 balances the progress of the reduction and passivation reactions.

[0063] In one optional embodiment, the conditions for the first cleaning are: a rotational speed of 5-20 rpm for the rotating electrode structure; a pulse frequency of 10-50 kHz; and a power density of 5-10 W / cm². 2 Processing time is 10-20 minutes.

[0064] Optionally, the rotational speed of the rotating electrode structure can be 5 rpm, 6 rpm, 7 rpm, 8 rpm, 9 rpm, 10 rpm, 11 rpm, 12 rpm, 13 rpm, 14 rpm, 15 rpm, 16 rpm, 17 rpm, 18 rpm, 19 rpm, or 20 rpm, or any value between 5 and 20 rpm; the pulse frequency can be 10 kHz, 15 kHz, 20 kHz, 25 kHz, 30 kHz, 35 kHz, 40 kHz, 45 kHz, or 50 kHz, or any value between 10 and 50 kHz; the power density can be 5 W / cm². 2 6W / cm 2 7W / cm 2 8W / cm 2 9W / cm 2 10W / cm 2 Or 5-10W / cm 2 Any value between.

[0065] In a vacuum environment, a rotating electrode rotates at 5-20 rpm, causing plasma to uniformly cover the inner wall of the pipe. A periodic high-energy electron flow is generated using pulses at a frequency of 10-50 kHz, allowing active particles to continuously impact the deposit interface. The power density is controlled at 5-10 W / cm². 2 Within this range, it can both break the chemical bonds in the silicon carbide layer and prevent secondary oxidation of metal oxides due to energy overload. Furthermore, by controlling the processing time, stubborn contaminants can be peeled off layer by layer, while preventing metal lattice damage caused by prolonged processing.

[0066] In one optional embodiment, the total flow rate of the second gas is 50-100 sccm, and the pressure is 0.5 × 10⁻⁶. -4 -2×10 -4 Torr, the time is 25-35 minutes.

[0067] Optionally, the total flow rate of the second gas can be 50 sccm, 55 sccm, 60 sccm, 65 sccm, 70 sccm, 75 sccm, 80 sccm, 85 sccm, 90 sccm, 95 sccm, or 100 sccm, or any value between 50 and 100 sccm; the pressure can be 0.5 × 10⁻⁶. -4 Torr, 0.6×10 -4 Torr, 0.7×10 -4 Torr, 0.8×10 -4 Torr, 0.9×10 -4 Torr, 1×10 -4 Torr, 1.1×10 -4 Torr, 1.2×10-4 Torr, 1.3×10 -4 Torr, 1.4×10 -4 Torr, 1.5×10 -4 Torr, 1.6×10 -4 Torr, 1.7×10 -4 Torr, 1.8×10 -4 Torr, 1.9×10 -4 Torr, 2×10 -4 Torr, or 0.5-2×10 -4 Any value between Torr, the time can be 25 minutes, 26 minutes, 27 minutes, 28 minutes, 29 minutes, 30 minutes, 31 minutes, 32 minutes, 33 minutes, 34 minutes, 35 minutes, or any value between 25 and 35 minutes.

[0068] Specifically, controlling the gas flow rate can prevent uneven gas distribution and the formation of cleaning blind zones due to excessively low flow rates, while also preventing excessively high flow rates from increasing the probability of gas molecule collisions and reducing reaction efficiency. By controlling the reaction pressure, the electron temperature and density in the plasma are optimized, allowing the active nitrogen atoms generated by N2 decomposition to work synergistically with H2 reduction to remove metal oxides.

[0069] In an optional embodiment, the collaborative cleaning method further includes a post-processing step, which includes: introducing O3 into the intake pipe to form a SiO2 passivation layer on the inner wall of the intake pipe, and monitoring the surface elemental composition inside the intake pipe.

[0070] In one optional embodiment, the post-treatment conditions are: O3 concentration of 100-200 ppm, reaction temperature of 50-80°C, and treatment time of 20-40 minutes.

[0071] Optionally, the O3 concentration can be 100ppm, 110ppm, 120ppm, 130ppm, 140ppm, 150ppm, 160ppm, 170ppm, 180ppm, 190ppm, 200ppm, or any value between 100-200ppm; the reaction temperature can be 50℃, 55℃, 60℃, 65℃, 70℃, 75℃, 80℃, or any value between 50-80℃; the treatment time can be 20min, 25min, 30min, 5min, 40min, or any value between 20-40min.

[0072] After physical cleaning, ozone is introduced into the pipe and reacts with residual silicon-based contaminants on the metal surface under heating conditions. During the reaction, silicon is oxidized to silicon dioxide, forming a continuous passivation layer on the metal surface. The formation of the passivation layer is tracked in real time by a spectral detection device, and processing is stopped when the silicon-oxygen ratio reaches a preset threshold. This passivation layer acts as a physical barrier, preventing direct contact between the reactant gases and the metal substrate in subsequent processes, while also sealing off any microscopic defects that may exist after cleaning.

[0073] Through the above technical solution, this application effectively solves the problem of surface regeneration pollution after metal pipe cleaning, avoids the repeated corrosion caused by lack of surface protection in traditional processes, and ensures the quality stability of the protective layer through real-time monitoring, thus extending the service life of the air intake pipe.

[0074] Secondly, this application also provides an apparatus for low-temperature plasma co-cleaning of an air inlet pipe, for performing the method of low-temperature plasma co-cleaning of the air inlet pipe, the apparatus for low-temperature plasma co-cleaning of the air inlet pipe including a modular cavity system and an intelligent sensing system.

[0075] The modular cavity comprises independent components:

[0076] Pretreatment chamber: used to pre-decompose organic matter and reduce the subsequent cleaning load;

[0077] Plasma cavity: used to improve the uniformity of plasma distribution;

[0078] Post-treatment chamber: used to form a surface passivation protective layer in the intake pipe;

[0079] The pretreatment chamber is equipped with an ultraviolet photocatalytic module; the plasma chamber adopts a rotating electrode structure; the posttreatment chamber includes an ozone generator and a humidity control device.

[0080] The intelligent sensing system includes:

[0081] LIBS online detection module: used for real-time analysis of contaminant composition on pipe walls and dynamic adjustment of cleaning parameters;

[0082] Pressure-flow closed-loop control system: Used in closed-loop control systems to ensure process stability.

[0083] The modular chamber system refers to a structural design that divides the cleaning process into three independent chambers. This can be achieved using stainless steel or quartz partitioned chambers, physically isolating different process stages to avoid cross-contamination of gases. The ultraviolet photocatalytic module is a device that uses specific wavelengths of ultraviolet light to excite photocatalytic reactions. This can be achieved using a mercury lamp or LED ultraviolet light source combined with a photocatalyst coating, used to decompose residual organic pollutants on the pipe wall. The rotating electrode structure is a discharge electrode assembly that can rotate around an axis. This can be achieved using a coaxial rotating mechanism driven by a servo motor, enhancing plasma uniformity through dynamic electric field distribution. The ozone generator is a device that produces ozone through high-voltage discharge or ultraviolet light decomposition of oxygen. This can be achieved using a dielectric barrier discharge unit, used to form a passivation layer on the pipe wall. The LIBS online detection module is a surface composition analysis device based on laser-induced breakdown spectroscopy. This can be achieved using a pulsed laser and spectrometer combined system, monitoring changes in surface elemental composition in real time during the cleaning process.

[0084] The pretreatment chamber uses active oxygen species generated by the ultraviolet photocatalysis module to pre-oxidize and decompose organic matter and metal oxides on the inner wall of the inlet pipe, reducing the difficulty of subsequent cleaning. The plasma chamber utilizes dynamic plasma generated by a rotating electrode structure to physically bombard and chemically etch the silicon carbide layer, combined with a pulsed discharge mode to reduce thermal damage. The post-treatment chamber uses ozone oxidation to form a dense passivation layer on the cleaned metal surface, while a humidity control device maintains a stable reaction environment. In the intelligent sensing system, the LIBS module analyzes the surface elemental composition in real time to determine the cleaning endpoint; the pressure-flow closed-loop system dynamically adjusts the gas flow rate and chamber pressure based on real-time monitoring data to ensure stable parameters at each process stage.

[0085] The implementation schemes of this application will be described in detail below with reference to specific embodiments. However, those skilled in the art will understand that the following embodiments are only for illustrating this application and should not be regarded as limiting the scope of this application. Unless otherwise specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments used without specified manufacturers are all conventional products that can be purchased commercially.

[0086] Example 1

[0087] This embodiment provides a method for cleaning an air inlet pipe using low-temperature plasma, and the specific steps are as follows:

[0088] The LPCVD silicon tube to be cleaned, the LPCVD silicon tube before cleaning is as follows: Figure 1 As shown, after sealing, a vacuum was drawn to an initial vacuum level of 1×10⁻⁶. -3 Torr, with the ultraviolet photocatalytic reaction gas O2 introduced, and the ultraviolet light source wavelength set to 254nm and intensity to 50mW / cm². 2The irradiation time was 30 minutes. The vacuum level was gradually reduced to 1×10⁻⁶ using a gradient pressure controller. -6 Torr creates a gradient vacuum environment.

[0089] The first cleaning process employed a three-electrode rotating structure (anode-rotating cathode-grounding ring), with a 4:1 volume ratio of Ar and H2 gas introduced. The rotating electrode rotation speed was set to 10 rpm, the pulse frequency to 30 kHz, and the power density to 8 W / cm². 2 The processing time is 15 minutes. The plasma is confined by a magnetic field, enhancing the physical bombardment and chemical decomposition of deposits on the pipe wall.

[0090] For the second cleaning, the gas mixture of Ar, H2, and N2 with a volume ratio of 5:3:2 was switched to a total flow rate of 75 sccm and a pressure of 1×10⁻⁶. -4 Torr, duration 30 minutes.

[0091] O3 at a concentration of 150 ppm was introduced at a temperature of 70°C for 30 minutes. The cleaned LPCVD silicon tube is shown below. Figure 2 As shown in Table 1, the surface elemental composition was monitored in real time using LIBS (laser-induced breakdown spectroscopy), and the ozone flow was controlled in a closed loop.

[0092] Table 1. Elemental analysis of surfaces using LIBS online detection.

[0093]

[0094] Example 2

[0095] This embodiment provides a method for cleaning an air inlet pipe using low-temperature plasma, and the specific steps are as follows:

[0096] After sealing the silicon nitride coated tube to be cleaned, evacuate it to an initial vacuum level of 1×10⁻⁶. -3 Torr, with the ultraviolet photocatalytic reaction gas O2 introduced, and the ultraviolet light source wavelength set to 254nm and intensity to 50mW / cm². 2 The irradiation time was 30 minutes. The vacuum level was gradually reduced to 1×10⁻⁶ using a gradient pressure controller. -6 Torr creates a gradient vacuum environment.

[0097] The first cleaning process employed a three-electrode rotating structure (anode-rotating cathode-grounding ring), with a 4:1 volume ratio of Ar and H2 gas introduced. The rotating electrode rotation speed was set to 5 rpm, the pulse frequency to 10 kHz, and the power density to 5 W / cm². 2 The processing time is 10 minutes. The plasma is confined by a magnetic field, enhancing the physical bombardment and chemical decomposition of deposits on the pipe wall.

[0098] For the second cleaning, the gas mixture of Ar, H2, and N2 with a volume ratio of 5:3:2 was switched to a total flow rate of 50 sccm and a pressure of 1 × 10⁻⁶. -4 Torr, duration 30 minutes.

[0099] O3 at a concentration of 100 ppm was introduced at a temperature of 50°C for 20 minutes. Surface elemental composition was monitored in real time using LIBS, and ozone flow was controlled in a closed-loop manner.

[0100] Example 3

[0101] This embodiment provides a method for cleaning an air inlet pipe using low-temperature plasma, and the specific steps are as follows:

[0102] After sealing the polysilicon tube to be cleaned, evacuate it to an initial vacuum level of 1×10⁻⁶. -3 Torr, with the ultraviolet photocatalytic reaction gas O2 introduced, and the ultraviolet light source wavelength set to 254nm and intensity to 50mW / cm². 2 The irradiation time was 60 minutes. The vacuum level was gradually reduced to 1×10⁻⁶ using a gradient pressure controller. -6 Torr creates a gradient vacuum environment.

[0103] The first cleaning process employed a three-electrode rotating structure (anode-rotating cathode-grounding ring), with a 4:1 volume ratio of Ar and H2 gas introduced. The rotating electrode rotation speed was set to 20 rpm, the pulse frequency to 50 kHz, and the power density to 10 W / cm². 2 The processing time is 20 minutes. The plasma is confined by a magnetic field, enhancing the physical bombardment and chemical decomposition of deposits on the tube wall.

[0104] For the second cleaning, the gas mixture of Ar, H2, and N2 with a volume ratio of 5:3:2 was switched to a total flow rate of 100 sccm and a pressure of 1 × 10⁻⁶. -4 Torr, duration 30 minutes.

[0105] O3 at a concentration of 200 ppm was introduced at a temperature of 80°C for 40 minutes. Surface elemental composition was monitored in real time using LIBS, and ozone flow was controlled in a closed-loop manner.

[0106] Comparative Example 1

[0107] This comparative example provides a method for cleaning an air inlet pipe using low-temperature plasma, the specific steps of which are as follows:

[0108] After sealing the LPCVD silicon tube to be cleaned, evacuate it to an initial vacuum level of 1×10⁻⁶. -3 Torr, with the ultraviolet photocatalytic reaction gas O2 introduced, and the ultraviolet light source wavelength set to 254nm and intensity to 50mW / cm². 2The irradiation time was 30 minutes. The vacuum level was gradually reduced to 1×10⁻⁶ using a gradient pressure controller. -6 Torr creates a gradient vacuum environment.

[0109] The cleaning process was performed using a mixture of Ar, H2, and N2 in a volume ratio of 5:3:2, with a total flow rate of 75 sccm and a pressure of 1 × 10⁻⁶. -4 Torr, duration 30 minutes.

[0110] O3 at a concentration of 150 ppm (100-200) was introduced at a temperature of 70°C for 30 minutes. Surface elemental composition was monitored in real time using LIBS, and ozone flow was controlled in a closed-loop manner.

[0111] Comparative Example 2

[0112] This embodiment provides a method for cleaning an air inlet pipe using low-temperature plasma, and the specific steps are as follows:

[0113] After sealing the LPCVD silicon tube to be cleaned, evacuate it to an initial vacuum level of 1×10⁻⁶. -3 Torr, with the ultraviolet photocatalytic reaction gas O2 introduced, and the ultraviolet light source wavelength set to 254nm and intensity to 50mW / cm². 2 The irradiation time was 30 minutes. The vacuum level was gradually reduced to 1×10⁻⁶ using a gradient pressure controller. -6 Torr creates a gradient vacuum environment.

[0114] Cleaning was performed using a three-electrode rotating structure (anode-rotating cathode-grounding ring), with a 4:1 volume ratio of Ar and H2 mixed gas introduced. The rotating electrode speed was set to 10 rpm, the pulse frequency to 30 kHz, and the power density to 8 W / cm². 2 The processing time is 15 minutes. The plasma is confined by a magnetic field, enhancing the physical bombardment and chemical decomposition of deposits on the pipe wall.

[0115] O3 at a concentration of 150 ppm was introduced at a temperature of 70°C for 30 minutes. Surface elemental composition was monitored in real time using LIBS, and ozone flow was controlled in a closed-loop manner.

[0116] Comparative Example 3

[0117] This comparative example provides a conventional acid pickling and cleaning method for air intake pipes, with the following specific steps:

[0118] The LPCVD silicon tubes were soaked in a mixed acid solution of HF and HNO3 (pH 2.5) for 300 minutes. The cleaned LPCVD silicon tubes showed the following results: Figure 3 As shown.

[0119] Table 1 shows the residual amount information after cleaning provided in the embodiments and comparative examples:

[0120] Table 2. Residual amount information after cleaning in the embodiments and comparative examples.

[0121]

[0122] As shown in Table 2, the metal residue in the examples was lower than that in the comparative examples, indicating that real-time monitoring via LIBS ensured precise adjustment of ozone flow, avoiding secondary pollution from metal residue. The thickness loss in Examples 1-3 was only 1.8-2.1 μm, indicating that the gradient vacuum environment and synergistic cleaning (plasma + ozone) caused minimal mechanical damage to the pipe wall. In Comparative Examples 1 and 2, the thickness loss was 4.5-5.7 μm, indicating that the omission of the gradient vacuum or plasma steps led to increased physical bombardment during the cleaning process. In Comparative Example 3, acid washing resulted in a 12.3 μm thickness loss, and HF caused severe corrosion of the pipe wall.

[0123] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

[0124] Furthermore, those skilled in the art will understand that although some embodiments herein include certain features included in other embodiments but not others, combinations of features from different embodiments are intended to be within the scope of this application and form different embodiments. For example, in the foregoing claims, any of the claimed embodiments can be used in any combination. The information disclosed in this background section is intended only to enhance the understanding of the general background of this application and should not be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

Claims

1. A method for cleaning an air inlet pipe using low-temperature plasma, characterized in that, include: The intake pipe to be cleaned is pretreated with ultraviolet photocatalysis in a vacuum environment; After the pretreatment, a first gas is introduced and a rotating electrode pulsed plasma is used for the first cleaning. The intake pipe, which has undergone the first cleaning, is then purged with a second gas for a second cleaning. The first gas includes Ar and H2; The second gas includes Ar, H2 and N2.

2. The method for low-temperature plasma-assisted cleaning of the air inlet pipe according to claim 1, characterized in that, The vacuum environment is a gradient vacuum environment, and the initial vacuum level in the gradient vacuum environment is 0.5 × 10⁻⁶. -3 -2×10 -3 Torr, the final vacuum level is 1×10 -6 -2×10 -6 Torr.

3. The method for low-temperature plasma-assisted cleaning of the air inlet pipe according to claim 2, characterized in that, Once the vacuum level in the intake pipe reaches the initial vacuum level, the ultraviolet photocatalytic pretreatment is performed.

4. The method for low-temperature plasma-assisted cleaning of the air inlet pipe according to claim 3, characterized in that, The conditions for the ultraviolet photocatalytic pretreatment are as follows: the reaction gas includes O2 or gaseous H2O; the ultraviolet light source wavelength is 254 nm, and the intensity is not less than 50 mW / cm². 2 The irradiation time is 30-60 minutes.

5. The method for low-temperature plasma-assisted cleaning of the air inlet pipe according to claim 1, characterized in that, At least one of the following conditions must be met: a. In the first gas, the volume ratio of Ar to H2 is 4-5:1; b. In the second gas, the volume ratio of Ar, H2 and N2 is 4-5:2-3:1-2.

6. The method for low-temperature plasma-assisted cleaning of the air inlet pipe according to claim 1, characterized in that, The conditions for the first cleaning are: a rotational speed of 5-20 rpm for the rotating electrode structure; a pulse frequency of 10-50 kHz; and a power density of 5-10 W / cm². 2 Processing time is 10-20 minutes.

7. The method for low-temperature plasma-assisted cleaning of the air inlet pipe according to claim 1, characterized in that, The total flow rate of the second gas is 50-100 sccm, and the pressure is 0.5 × 10⁻⁶. -4 -2×10 -4 Torr, the time is 25-35 minutes.

8. The method for low-temperature plasma-assisted cleaning of the air inlet pipe according to any one of claims 1-7, characterized in that, The method for co-cleaning the air intake pipe with low-temperature plasma also includes post-processing, which includes: introducing O3 into the air intake pipe to form a SiO2 passivation layer on the inner wall of the air intake pipe, and monitoring the surface elemental composition inside the air intake pipe.

9. The method for low-temperature plasma-assisted cleaning of the air inlet pipe according to claim 8, characterized in that, The post-treatment conditions are: O3 concentration of 100-200 ppm, reaction temperature of 50-80℃, and treatment time of 20-40 minutes.

10. A device for co-cleaning an air inlet pipe using low-temperature plasma, characterized in that, The method for performing the cryogenic plasma co-cleaning of the inlet pipe according to any one of claims 1-9, wherein the apparatus for cryogenic plasma co-cleaning of the inlet pipe includes a modular cavity system and an intelligent sensing system; The modular cavities include independent components. Pretreatment chamber: used to pre-decompose organic matter and reduce the subsequent cleaning load; Plasma cavity: used to improve the uniformity of plasma distribution; Post-treatment chamber: used to form a surface passivation protective layer in the intake pipe; The pretreatment chamber is equipped with an ultraviolet photocatalytic module; the plasma chamber adopts a rotating electrode structure; the posttreatment chamber includes an ozone generator and a humidity control device. The intelligent sensing system includes, LIBS online detection module: used for real-time analysis of contaminant composition on pipe walls and dynamic adjustment of cleaning parameters; Pressure-flow closed-loop control system: Used in closed-loop control systems to ensure process stability.

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