Positive pressure purging device for maintenance of epitaxial furnace tail gas pipeline and control method thereof

Abstract

The application relates to a positive pressure purging device for maintenance of an epitaxial furnace tail gas pipeline and a control method thereof, and belongs to the technical field of maintenance of silicon wafer processing equipment. The device comprises an epitaxial furnace, a washing tower and a connecting pipe connecting the two, a one-way valve and a pressure gauge are arranged on the connecting pipe; a nitrogen gas conveying pipe is arranged at the upper end of the washing tower, and a float flowmeter and a hand valve are arranged on the pipe. The main body corrugated pipeline is removed, a standardized adapter composed of a flange plate, a hand valve, a nitrogen gas conveying pipe and a flowmeter is installed at the original blind plate position; the hand valve is opened to introduce nitrogen gas and adjust the flow to continuously purging; the pipeline pressure is monitored through the pressure gauge, and the one-way valve is used to prevent gas backflow; after continuous purging for a preset time, the washing tower scraper is safely removed for maintenance. The pipeline is filled with inert gas through positive pressure nitrogen replacement, the triggering conditions of B2H6 / PH3 residue and TCS hydrolysis hydrogen explosion or explosion in air are completely eliminated, the adapter is prefabricated and can be reused, and the safety and efficiency of the maintenance operation are greatly improved.

Description

Technical Field

[0001] This invention relates to the field of silicon wafer processing equipment maintenance technology, specifically to a positive pressure purging device and its control method for maintaining the exhaust gas pipeline of an epitaxial furnace. Background Technology

[0002] Large quantities are required in silicon epitaxy processes. TCS (trichlorosilane), HCl , Gases, including TCS, , All of these are highly toxic or spontaneously combustible gases, and their exhaust gases must be treated by a water-washing exhaust gas processor (scrubber) before being released. During the water washing process, TCS reacts with water to produce powdery / flocculated substances. Byproducts will continuously adhere to and clog the air inlet and pipelines, causing a drop in negative pressure inside the epitaxial furnace and preventing normal growth of the epitaxial layer. It is necessary to periodically stop the machine and disassemble the scraper for preventive maintenance.

[0003] Traditional maintenance methods have three major drawbacks: First, it takes about an hour after shutdown to open the exhaust pipe, which is time-consuming and ties up production capacity; second, when the pipe is disassembled, residual gases... With TCS hydrolysis If exposed to air, it is highly susceptible to flashover or explosion; thirdly, repeated disassembly and reassembly of clamps and blind flanges can easily lead to air leakage at the interfaces, resulting in high maintenance complexity.

[0004] To improve the production efficiency of the epitaxial furnace and reduce equipment downtime, preventative maintenance was performed on the main epitaxial furnace chamber, and preventative maintenance was also performed on the auxiliary equipment, the CIRECO brand wet exhaust gas scrubber. Because the water scrubber was sealed with a KF40 blind flange (exhaust to the scrubber port) after the epitaxial furnace chamber and exhaust gas pipelines were removed, the removal of some pipelines at the furnace chamber end resulted in a lack of safety purging gas to continuously purge the remaining pipelines (before the pipelines were removed, the chamber provided continuous purging gas). ); the residual B2H6 or PH3 and TCS in the pipeline after volatilization If the scrubber is removed and then comes into contact with air, it may ignite or explode, resulting in personal injury and property damage.

[0005] A scrubber is an industrial waste gas treatment device primarily used to remove harmful, toxic, corrosive, or flammable chemicals from gas streams, ensuring that the gases meet safety and environmental standards before being released into the atmosphere or entering the next stage of treatment. A scrubber can be a scrubbing tower, exhaust gas scrubber, or exhaust gas treatment device.

[0006] The exhaust gas from the epitaxial process contains TCS, HCl, , Highly toxic / flammable and explosive gases, among which Its explosive limits in air are wide, ranging from 0.8% to 88%. The percentage ranges from 4% to 75.6%. All three are highly toxic and flammable, making them extremely dangerous special gases. Water-washable scrubbers can only absorb water-soluble components (TCS, HCl, etc.). , ), exhaust gas The content can reach about 99%, which is close to the processing limit of combustion equipment, and it is extremely sensitive to ignition sources.

[0007] The existing practice of using KF40 blind flanges to seal the Scrubber port openings and then removing the scraper for preventative maintenance has the following fatal flaws: The purge gas supply was cut off: After the outer furnace cavity and the front-end pipeline of the bellows were removed, the continuous gas supply originally provided by the cavity was cut off. Once the purge gas source disappears, a "dead space" is formed in the remaining section of the pipeline leading to the Scrubber.

[0008] Residual gas cannot be replaced: unreacted gas deposited on the inner wall of the pipeline. , And the combustibles generated by the reaction of TCS with trace amounts of water vapor The powder cannot be replaced by inert gas and remains in a static enrichment state.

[0009] Air is introduced upon removal: the blind flange sealing only provides physical isolation; once the scraper / pipe is opened for PM (air) treatment, air ( Instantly, it flowed back into the dead space containing flammable gas. Low auto-ignition point ( It can spontaneously combust at room temperature in air. Within the explosive limits, it is extremely easy to trigger flashover or deflagration.

[0010] No positive pressure barrier: The blind flange does not establish positive pressure inside the pipe, cannot prevent backflow of external air, and cannot monitor online whether the atmosphere inside the pipe has been inertized. Summary of the Invention

[0011] This invention addresses the shortcomings of existing technologies by providing a positive pressure purging device and its control method for maintenance of epitaxial furnace tail gas pipelines. The device fills the pipeline with inert gas through positive pressure nitrogen replacement, completely eliminating the triggering conditions for the combustion or explosion of B2H6 / PH3 residues and TCS hydrolysis hydrogen production upon contact with air. Furthermore, the adapter is prefabricated and reusable, eliminating the need for on-site drilling and significantly improving the safety and efficiency of maintenance operations.

[0012] The above-mentioned technical problems of the present invention are mainly solved by the following technical solutions: A positive pressure purging device for maintenance of exhaust gas pipeline of epitaxial furnace includes an epitaxial furnace, a scrubbing tower is provided on the side of the epitaxial furnace, a connecting pipe is provided between the upper part of the scrubbing tower and the epitaxial furnace, a nitrogen delivery pipe connected to the scrubbing tower is provided at the upper end of the scrubbing tower, a float flow meter is provided on the nitrogen delivery pipe, and a hand valve connected to the nitrogen delivery pipe by a flange is provided between the float flow meter and the scrubbing tower.

[0013] Preferably, the connecting pipe is equipped with a one-way valve, and a pressure gauge is provided between the one-way valve and the epitaxial furnace, which is threadedly sealed to the connecting pipe.

[0014] Preferably, flange plates are provided between both ends of the hand valve and the nitrogen delivery pipe, and between both ends of the check valve and the connecting pipe.

[0015] Preferably, the washing tower is equipped with a drain valve at the bottom.

[0016] A control method for a positive pressure purging device includes the following operating steps: Step 1: Remove the main body of the epitaxial furnace and the front corrugated pipeline. Install a standardized and reusable nitrogen purging adapter at the original blind flange sealing position. The nitrogen purging adapter consists of a flange plate, a hand valve, a nitrogen delivery pipe, and a float flow meter. Then connect the scrubbing tower to the nitrogen delivery pipe.

[0017] Step 2: Open the manual valve on the nitrogen delivery pipe, adjust the nitrogen flow rate to the set flow rate using the float flow meter, and continuously purge nitrogen between the scrubbing tower and the epitaxial furnace and into the connecting pipe.

[0018] Step 3: Monitor the pressure inside the pipeline using the pressure gauge on the connecting pipe to ensure that the pipeline is kept under positive pressure. At the same time, use the one-way valve on the connecting pipe to prevent gas from flowing back into the pipeline and contaminating the nitrogen source.

[0019] Step 4: After the continuous positive pressure nitrogen purging has reached the preset time, remove the scraper of the scrubbing tower for preventive maintenance.

[0020] Preferably, the set nitrogen purging flow rate is 10 L / min, and the preset time for continuous positive pressure nitrogen purging is 10 minutes.

[0021] As a preferred method, the pipeline is continuously purged with positive pressure nitrogen to fill it with inert gas, thereby eliminating the triggering conditions for the B2H6 / PH3 residues in the pipeline and the H2 generated by TCS hydrolysis to ignite or explode upon contact with air.

[0022] As a preferred option, the standardized nitrogen purging adapter is a pre-drilled and welded flange connection that can be directly installed and replaced during each maintenance without the need for re-drilling.

[0023] The present invention can achieve the following effects: This invention provides a positive pressure purging device and its control method for maintenance of the tail gas pipeline of an epitaxial furnace. Compared with the prior art, it has the following significant advantages: I. Completely eliminate safety hazards and significantly improve maintenance safety. By continuously introducing nitrogen into the pipeline before maintenance to create a positive pressure inert environment, the oxygen (air) in the pipeline is actively replaced, fundamentally cutting off the risk of accidents. Residue and TCS hydrolysis Triggering conditions include flashover or explosion upon contact with air. Simultaneously, the one-way valve design effectively prevents residual hazardous gases in the pipe from flowing back to the nitrogen source, avoiding secondary pollution and explosion risks, and ensuring the absolute safety of operators when removing the scraper for maintenance.

[0024] II. Significantly reduces downtime and improves overall equipment efficiency (OEE). Traditional maintenance methods typically require a passive wait of about one hour after shutdown to allow hazardous gases in the pipelines to dissipate naturally before they can be opened. This invention employs an active positive pressure purging process, which only requires 10 minutes (10 L / min flow rate) to reach safe pipeline opening conditions, significantly reducing unplanned downtime waiting time for the epitaxial furnace and effectively improving equipment uptime and capacity.

[0025] Third, standardized operations are implemented to reduce manual labor intensity. The previously scattered purging pipelines are solidified into a "standardized nitrogen purging adapter." This adapter is pre-drilled and welded in the factory, and maintenance only requires replacing the original blind flange as a whole, eliminating the need for on-site cutting, drilling, and temporary assembly. This plug-and-play, reusable design not only simplifies the operation process and reduces manual labor intensity but also avoids damage to the sealing surface caused by repeated drilling.

[0026] IV. Controllable and traceable process parameters ensure consistent purging results. The integrated float flowmeter and pressure gauge transform the previously experience-based "blind purging" into a visual and quantifiable precise control. Operators can intuitively adjust the nitrogen flow rate to the set value (10 L / min) and monitor in real time whether the tube maintains a positive pressure state, ensuring consistent and reliable purging results for each maintenance, facilitating standardized process management and quality traceability. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the structure of the present invention.

[0028] In the diagram: 1. Epitaxial furnace; 2. Pressure gauge; 3. Connecting pipe; 4. Check valve; 5. Scrubber; 6. Flange plate; 7. Hand valve; 8. Nitrogen delivery pipe; 9. Float flow meter; 10. Drain valve. Detailed Implementation

[0029] The technical solution of the invention will be further described in detail below through embodiments and in conjunction with the accompanying drawings.

[0030] Example: Figure 1 As shown, a positive pressure purging device for maintaining the exhaust gas pipeline of an epitaxial furnace includes an epitaxial furnace 1. A scrubbing tower 5 is installed on the exhaust gas outlet side of the epitaxial furnace 1, and the two are connected by a connecting pipe 3. One end of the connecting pipe 3 is connected to the upper part of the scrubbing tower 5. A pressure gauge 2 and a one-way valve 4 are sequentially installed on the connecting pipe 3 along the gas flow direction (from the epitaxial furnace 1 to the scrubbing tower 5). The pressure gauge 2 is connected to the connecting pipe 3 by a threaded seal for real-time monitoring of the pressure inside the pipeline; the one-way valve 4 is used to prevent gas from the scrubbing tower 5 side from flowing back towards the nitrogen source.

[0031] The upper end of the scrubbing tower 5 is equipped with a nitrogen supply pipe 8 that communicates with the interior of the scrubbing tower 5. A float flow meter 9 and a manual valve 7 are sequentially installed on the nitrogen supply pipe 8. The manual valve 7 is located between the float flow meter 9 and the scrubbing tower 5, and both ends of the manual valve 7 are flanged to the nitrogen supply pipe 8, and both ends of the check valve 4 are flanged to the connecting pipe 3, so as to facilitate disassembly and modular maintenance.

[0032] In addition, a drain valve 10 is provided at the bottom of the washing tower 5 to discharge the washing liquid and by-product residue accumulated in the tower after maintenance.

[0033] In the actual epitaxial furnace tail gas treatment system, the original design would use a blind flange to block the tail gas outlet during shutdown maintenance, which would be replaced with a standardized nitrogen purging adapter. This adapter is an integral prefabricated module, consisting of a flange plate 6, a hand valve 7, a nitrogen delivery pipe 8, and a float flow meter 9. All components are pre-drilled and welded in the factory.

[0034] Whenever exhaust pipeline maintenance is required, the operator simply installs the pre-assembled standardized adapter at the original blind flange sealing position, and then connects the adapter's nitrogen delivery pipe 8 to an external high-purity nitrogen source. This standardized design eliminates the cumbersome operations of temporary drilling, cutting, and welding on-site, achieving plug-and-play functionality. Furthermore, the adapter is reusable, significantly improving the standardization and efficiency of maintenance operations.

[0035] A control method for a positive pressure purging device includes the following operating steps: Step 1: Piping Modification and Adapter Installation. When the semiconductor / photovoltaic epitaxial process is completed and a planned shutdown is performed for preventative maintenance, first remove the main body and front-end corrugated piping of epitaxial furnace 1 to expose the original blind flange sealing location. Directly install the standardized nitrogen purging adapter described in Example 2 (prefabricated from flange plate 6, hand valve 7, nitrogen delivery pipe 8, and float flow meter 9) to replace the original blind flange, ensuring that the scrubbing tower 5 is connected to the nitrogen delivery pipe 8.

[0036] Step 2: Initiate positive pressure purging. Slowly open the hand valve 7 on the nitrogen delivery pipe 8 to introduce high-purity nitrogen. Observe the rotor height of the float flowmeter 9 and adjust the nitrogen flow rate to the set purging flow rate, which is set to 10 L / min. At this time, high-purity nitrogen is continuously introduced into the cavity between the scrubbing tower 5 and the epitaxial furnace 1 and into the connecting pipe 3 for positive gas replacement purging.

[0037] Step 3: Positive Pressure Monitoring and Backflow Prevention. During the continuous nitrogen supply, the pressure inside the pipeline is monitored by pressure gauge 2 on connecting pipe 3 to ensure a continuous positive pressure (usually slightly higher than atmospheric pressure), preventing external air from seeping into the pipeline through tiny gaps. Simultaneously, the one-way valve 4 on connecting pipe 3 is engaged to effectively prevent residual exhaust gases (B2H6 / PH3 / H2, etc.) from flowing back and contaminating the nitrogen supply source.

[0038] Step 4: Safely remove the scraper for maintenance. After continuous positive pressure nitrogen purging for a preset time (set to 10 minutes), the oxygen in the pipeline is fully replaced, and the pipeline is filled with inert gas. This fundamentally eliminates the triggering conditions for flashover or explosion caused by highly toxic / spontaneously flammable gases (such as residual B2H6 / PH3) and H2 produced by TCS hydrolysis upon contact with air. At this time, the operator can safely remove the scraper of the scrubbing tower 5, open the drain valve 10 located at the bottom to discharge waste liquid and by-products, and perform a thorough preventative maintenance operation. After maintenance is completed, reconnecting the pipeline allows for rapid resumption of production.

[0039] To minimize downtime while ensuring safety, the optimal nitrogen purging flow rate was set at 10 L / min after process verification. This flow rate ensures sufficient gas velocity for effective replacement within the pipeline without causing short-circuiting or resource waste due to excessive velocity. The preset duration for continuous positive pressure nitrogen purging is 10 minutes, which is sufficient to reduce the concentration of hazardous residual gases in conventional diameter exhaust pipelines to below the safety threshold. By coordinating these parameters, a technological leap from "long-term natural diffusion waiting" to "ten-minute active inertial replacement" was achieved, significantly improving the safety and overall efficiency of the epitaxial equipment.

[0040] In summary, the positive pressure purging device and its control method for maintaining the exhaust gas pipeline of the epitaxial furnace, after the connecting pipeline between the epitaxial furnace and the scrubbing tower is disconnected, continuously introduces nitrogen into the pipeline through a standardized, reusable nitrogen purging adapter to form and maintain a positive pressure inert environment, thereby eliminating the root cause of the problem. The residual conditions and the triggering conditions for hydrogen production from TCS hydrolysis to ignite / explode upon contact with air allow subsequent preventative maintenance of the scraper to be performed under safe conditions.

[0041] Standardized adapters streamline processes. The traditional maintenance process of "drilling holes on-site, temporarily connecting pipes, and assembling valves piece by piece" is solidified into pre-welded flange connection modules, enabling plug-and-play and repeated use, significantly reducing maintenance time and the probability of human error per maintenance session.

[0042] The positive pressure + check valve bidirectional isolation design. The pressure gauge actively confirms the positive pressure, and the check valve passively blocks backflow, which not only prevents external air from infiltrating and causing flashover, but also prevents exhaust gas from backflowing and polluting the nitrogen source, thus solving the hidden dangers of traditional "only blowing without monitoring" or "only installing valves without monitoring".

[0043] Fixed parameters ensure repeatability. The combination of 10L / min flow rate × 10min time quantifies the "about right" approach that originally relied on engineers' experience into verifiable and traceable standard process parameters, making it easier to incorporate into SOPs and maintenance records.

[0044] The shift from "waiting for natural diffusion" to "active inertial displacement" significantly reduces downtime and directly improves the OEE of epitaxial machines compared to the industry's traditional passive approach of "shutting down for 1 hour before opening the tube".

[0045] The above description is only a specific embodiment of the present invention, but the structural features of the present invention are not limited thereto. Any changes or modifications made by those skilled in the art within the scope of the present invention are covered by the patent scope of the present invention.

Claims

1. A positive pressure purging device for maintenance of the exhaust gas pipeline of an epitaxial furnace, comprising an epitaxial furnace (1), characterized in that: The epitaxial furnace (1) is provided with a washing tower (5) on its side. A connecting pipe (3) is provided between the upper part of the washing tower (5) and the epitaxial furnace (1). A nitrogen supply pipe (8) is provided at the upper end of the washing tower (5) and is connected to the washing tower (5). A float flow meter (9) is provided on the nitrogen supply pipe (8). A hand valve (7) is provided between the float flow meter (9) and the washing tower (5) and is connected to the nitrogen supply pipe (8) by a flange.

2. The positive pressure purging device for maintenance of the tail gas pipeline of an epitaxial furnace according to claim 1, characterized in that: The connecting pipe (3) is equipped with a one-way valve (4), and a pressure gauge (2) is provided between the one-way valve (4) and the epitaxial furnace (1) and is connected to the connecting pipe (3) by a threaded seal.

3. The positive pressure purging device for maintenance of the tail gas pipeline of an epitaxial furnace according to claim 2, characterized in that: Flange plates (6) are provided between the two ends of the hand valve (7) and the nitrogen delivery pipe (8), and between the two ends of the check valve (4) and the connecting pipe (3).

4. The positive pressure purging device for maintenance of the tail gas pipeline of an epitaxial furnace according to claim 1, characterized in that: The washing tower (5) is equipped with a drain valve (10) at the bottom.

5. A control method for the positive pressure purging device according to claim 3, characterized in that... The following steps are included: Step 1: Remove the main body and front corrugated pipeline of the epitaxial furnace (1), and install a standardized and reusable nitrogen purging adapter at the original blind plate sealing position. The nitrogen purging adapter consists of a flange plate (6), a hand valve (7), a nitrogen delivery pipe (8) and a float flow meter (9). Then connect the scrubbing tower (5) to the nitrogen delivery pipe (8). Step 2: Open the hand valve (7) on the nitrogen delivery pipe (8), adjust the nitrogen flow rate to the set flow rate through the float flow meter (9), and continuously purge nitrogen between the scrubbing tower (5) and the epitaxial furnace (1) and into the connecting pipe (3); Step 3: Monitor the pressure inside the pipeline by using the pressure gauge (2) on the connecting pipe (3) to ensure that the pipeline is kept under positive pressure. At the same time, use the one-way valve (4) on the connecting pipe (3) to prevent the gas inside the pipeline from flowing back and contaminating the nitrogen source. Step 4: After the nitrogen purge under continuous positive pressure has reached the preset time, remove the scraper of the scrubbing tower (5) for preventive maintenance.

6. The control method of the positive pressure purging device according to claim 5, characterized in that: The set nitrogen purging flow rate is 10 L / min, and the preset time for continuous positive pressure nitrogen purging is 10 minutes.

7. The control method of the positive pressure purging device according to claim 5, characterized in that: By continuously purging with positive pressure nitrogen, the pipeline is filled with inert gas to eliminate the triggering conditions for the B2H6 / PH3 residue in the pipeline and the H2 generated by TCS hydrolysis to ignite or explode upon contact with air.

8. The control method of the positive pressure purging device according to claim 5, characterized in that: The standardized nitrogen purging adapter is a pre-drilled and welded flange connection that can be directly installed and replaced during each maintenance without the need for re-drilling.

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