Exhaust method after drawing heavily phosphorus-doped silicon single crystal

Abstract

The invention provides an exhaust method after drawing heavily phosphorus-doped silicon single crystals, and relates to the technical field of monocrystalline silicon production.The method comprises the steps that before an isolation valve between an upper furnace barrel and a lower furnace barrel is opened, the flow of inert gas and the opening degree of an APC valve or a manual valve used for balancing and adjusting the furnace pressure are adjusted, and then the silicon single crystals are exhausted; replacing air in the upper furnace barrel of the single crystal furnace with the inert gas; and after the isolating valve between the upper furnace barrel and the lower furnace barrel is opened, air is introduced into the single crystal furnace, red phosphorus in the phosphorus mixture in the exhaust pipeline of the single crystal furnace is slowly and fully combusted after making contact with the air, and the phosphorus mixture adsorbed on the inner wall of the exhaust pipeline is blown to be peeled off by conducting continuous opening and closing operation on the vacuum ball valve. According to the scheme, the explosion probability during exhausting can be reduced after the heavily phosphorus-doped single crystal is drawn, and the production safety is improved.

Description

Technical Field

[0001] The invention relates to the technical field of single crystal silicon production, and in particular to an exhaust method after pulling a heavily phosphorus-doped silicon single crystal. Background Art

[0002] In the semiconductor industry, the single crystal furnace is an important equipment for growing silicon single crystals. The quartz crucible in the single crystal furnace is used to hold polycrystals. A certain amount of dopant is added to the polycrystals. Through the processes of melting, seeding, shoulder release, shoulder rotation, equal-diameter growth, and finishing, products that meet customer requirements can be produced.

[0003] With the development of integrated circuit technology and applications, especially the increasingly lower power consumption requirements of power devices, lower resistivity requirements are put forward for single crystal silicon substrates. The solid solubility of dopants in silicon determines the limit resistivity of this type of single crystal substrate. At present, the dopants of N-type silicon single crystals in the industry are mainly arsenic and antimony, but after adding arsenic and antimony elements, the resistivity of the obtained single crystal silicon often does not meet the required requirements. Since phosphorus has a greater solid solubility in the silicon lattice, it helps to obtain single crystal silicon with lower resistivity, so heavily phosphorus-doped silicon single crystals came into being, and the market demand is also increasing.

[0004] However, the red phosphorus required for doping has a very low ignition point. During the doping and pulling process of heavily doped phosphorus single crystals, part of the dopant red phosphorus volatilizes and is mixed with its oxide phosphorus pentoxide and deposited in the vacuum pipe. When the production is finished, if the isolation valve between the upper and lower furnace drums is opened, a large amount of air will enter the pipe and react chemically with the red phosphorus in the phosphorus mixture, causing the phosphorus mixture to spontaneously ignite, especially the phosphorus mixture adsorbed in the dead corners or on the inner wall of the exhaust pipe, which is more likely to cause an explosion, thereby endangering the personal safety of workers and equipment in actual work. Summary of the invention

[0005] In view of this, in order to address the above shortcomings, it is necessary to propose an exhaust method after pulling a heavily phosphorus-doped silicon single crystal, so as to reduce the probability of explosion during exhaust after pulling a heavily phosphorus-doped silicon single crystal and improve production safety.

[0006] The present invention provides an exhaust method after pulling a heavily phosphorus-doped silicon single crystal. Before opening an isolation valve between an upper furnace drum and a lower furnace drum, the inert gas flow rate and the opening of an APC valve or a manual valve for balancing and adjusting the furnace pressure are adjusted to allow the inert gas to replace the air in the upper furnace drum of a single crystal furnace; and after opening the isolation valve between the upper furnace drum and the lower furnace drum, air is introduced into the single crystal furnace to allow the red phosphorus in the phosphorus mixture in the exhaust pipe of the single crystal furnace to slowly and fully burn after contacting with the air, and the phosphorus mixture adsorbed on the inner wall of the exhaust pipe is blown off by continuously switching the vacuum ball valve.

[0007] Preferably, the exhaust method specifically includes: Step S1, pre-operation after the crystal ingot is taken out: close the isolation valve between the upper furnace drum and the lower furnace drum, and quickly close the upper furnace drum after the crystal ingot is taken out to ensure a stable atmosphere in the single crystal furnace; Step S2, high vacuum gauge isolation operation: close the needle valve at the bottom of the high vacuum gauge to ensure that the high vacuum gauge is not disturbed during the inert gas replacement process; wherein the needle valve is a valve added to the bottom of the high vacuum gauge in the exhaust pipeline, which is used to prevent the inert gas replacement process from interfering with the high vacuum gauge; Step S3, inert gas replacement operation: the furnace pressure of the single crystal furnace is regulated and controlled by adjusting the inert gas flow rate, the opening of the APC valve and / or the manual valve, so as to replace the air in the furnace drum of the single crystal furnace with the inert gas; wherein the manual valve is a manual valve added before the main valve of the exhaust pipeline of the single crystal furnace, which is used to assist in regulating the furnace pressure; Step S4, combustion operation of the phosphorus mixture in the exhaust pipe: after opening the isolation valve, introducing air into the single crystal furnace, and maintaining the furnace pressure of the single crystal furnace by adjusting the opening of the APC valve and the opening of the manual valve, so that the phosphorus mixture burns slowly and fully; and the vacuum ball valve is quickly opened and closed at least twice to blow off the phosphorus mixture adsorbed on the inner wall of the exhaust pipe; Step S5, exhaust and furnace opening operation.

[0008] Preferably, in step S1, after the crystal rod is taken out and the upper furnace drum is closed, an airtightness check is performed to ensure that the single crystal furnace has no leakage.

[0009] Preferably, the step S3 specifically includes: The inert gas flow rate was initially set to 50±2slm, the APC valve opening was set to 30±0.5 degrees, and the inert gas replacement process was started; Adjust the inert gas flow rate to 50±2slm and the APC valve opening to 30±0.5 degrees, and maintain the first preset time.

[0010] Preferably, the step S3 specifically includes: The inert gas flow rate is initially set to 50±2slm, the APC valve opening is set to 30±0.5 degrees, and the inert gas replacement process is started; The inert gas flow rate is adjusted to 40±2slm, the APC valve opening is adjusted to 30±0.5 degrees, and the manual valve is adjusted to keep the furnace pressure at 20-25kPa for the second preset time.

[0011] Preferably, the step S3 specifically includes: The inert gas flow rate is initially set to 50±2slm, the APC valve opening is set to 30±0.5 degrees, and the inert gas replacement process is started; The inert gas flow rate is adjusted to 30±2slm, and the manual valve is adjusted to keep the furnace pressure at 20-25kPa for a third preset time period.

[0012] Preferably, in step S4, after the isolation valve is opened, air is introduced into the single crystal furnace, and the furnace pressure of the single crystal furnace is maintained by adjusting the opening of the APC valve and the opening of the manual valve, including: Close the inert gas supply, open the valve for letting in air, keep the APC valve opening at 30±0.5 degrees, and increase the manual valve opening to maintain the furnace pressure at 20-25kPa; and, Maintaining a fourth preset time period under the condition; During the fourth preset time period, the furnace pressure change is monitored in real time, and the furnace pressure is maintained by adjusting the opening of the manual valve.

[0013] Preferably, in step S4, the rapid opening and closing operation of the vacuum ball valve at least twice comprises: The vacuum ball valve is opened and closed six times at preset time intervals to blow off the phosphorus mixture accumulated and adsorbed on the inner wall of the exhaust pipe, and the phosphorus mixture is burned after being fully contacted with air.

[0014] Preferably, the step S5 comprises: Close the APC valve, stop the inert gas supply, and prepare for exhaust; Close the manual valve to stop the gas flow and prepare to start the furnace; Open the furnace after reaching normal pressure.

[0015] Preferably, the inert gas is argon.

[0016] It can be seen from the above technical scheme that when exhausting after pulling heavily phosphorus-doped single crystals, this scheme considers adjusting the inert gas flow rate and the opening of the APC valve or manual valve used to balance the furnace pressure so that the inert gas replaces the air in the single crystal furnace, and then introduces air to slowly and fully burn the phosphorus mixture in the exhaust pipe of the single crystal furnace. In this way, the inert gas replacement ensures that the uncontrollable amount of air in the upper furnace barrel after the isolation valve is opened will spontaneously combust after contacting the phosphorus mixture in the pipeline, thereby avoiding violent combustion of the phosphorus mixture and even explosion. Furthermore, this scheme considers rapidly and continuously switching the vacuum ball valve to blow off the phosphorus mixture adsorbed on the inner wall of the exhaust pipe, avoiding the accumulation of the phosphorus mixture at the valve, dead corner and other locations on the inner wall of the pipe, so that the phosphorus mixture adsorbed on the inner wall can be fully mixed with the air, ensuring that the phosphorus mixture is fully burned. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 A flow chart of an exhaust method after pulling a heavily phosphorus-doped silicon single crystal provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0018] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0019] At present, after the silicon single crystal is pulled, the conventional exhaust operation can be carried out directly after the single crystal is taken out. However, for the pulling of heavily phosphorus-doped single crystals, red phosphorus and its phosphorus mixture will be adsorbed in the vacuum pipe due to the volatilization of red phosphorus and other reasons. If the air is directly introduced in the conventional way, on the one hand, part of the air will inevitably be brought in when the crystal rod is taken, resulting in an unknown amount of air in the furnace, and the combustion controllability of the phosphorus mixture is poor, which is prone to generate a large amount of heat instantly, affecting the furnace pressure change and causing changes. On the other hand, the phosphorus mixture is often adsorbed at the four corners of the inner wall of the exhaust pipe, such as the ball valve, and the phosphorus mixture adsorbed in these places is often difficult to fully burn. Based on this, this scheme considers adjusting the inert gas flow rate and the opening of the APC valve or manual valve used to balance and adjust the furnace pressure before opening the isolation valve between the upper furnace drum and the lower furnace drum, so that the inert gas replaces the air in the upper furnace drum of the single crystal furnace; and after opening the isolation valve between the upper furnace drum and the lower furnace drum, air is introduced into the single crystal furnace so that the red phosphorus in the phosphorus mixture in the exhaust pipe of the single crystal furnace contacts with the air and burns slowly and fully, and the phosphorus mixture adsorbed on the inner wall of the exhaust pipe is blown off by continuously switching the vacuum ball valve. In this way, the inert gas replacement ensures that the amount of air introduced during the subsequent air introduction is relatively controllable, avoiding the introduction of unknown air volume to cause violent combustion of the phosphorus mixture, and even explosion. Further, it is considered to blow off the phosphorus mixture adsorbed on the inner wall of the exhaust pipe by rapidly and continuously switching the vacuum ball valve, avoiding the phosphorus mixture from accumulating at the valve, dead corner and other locations on the inner wall of the pipe, so that the phosphorus mixture adsorbed on the inner wall can be fully mixed with the air, ensuring that the phosphorus mixture is fully burned.

[0020] Specifically, in this solution, when exhausting after pulling a heavily phosphorus-doped silicon single crystal, Figure 1 As shown, this can be achieved as follows: Step S1, pre-operation after the crystal ingot is taken out: close the isolation valve between the upper furnace drum and the lower furnace drum, and quickly close the upper furnace drum after the crystal ingot is taken out to ensure a stable atmosphere in the single crystal furnace; Step S2, high vacuum gauge isolation operation: close the needle valve at the bottom of the high vacuum gauge to ensure that the high vacuum gauge is not disturbed during the inert gas replacement process; wherein the needle valve is a valve added to the bottom of the high vacuum gauge in the exhaust pipeline, which is used to prevent the inert gas replacement process from interfering with the high vacuum gauge; Step S3, inert gas replacement operation: the furnace pressure of the single crystal furnace is regulated and controlled by the inert gas flow rate, the opening of the APC valve and / or the manual valve, so as to replace the air in the furnace drum of the single crystal furnace with the inert gas; wherein the manual valve is a manual valve added before the main valve of the exhaust pipeline of the single crystal furnace, which is used to assist in regulating the furnace pressure; Step S4, combustion operation of the phosphorus mixture in the exhaust pipe: after opening the isolation valve, introducing air into the single crystal furnace, and maintaining the furnace pressure of the single crystal furnace by adjusting the opening of the APC valve and the opening of the manual valve, so that the phosphorus mixture burns slowly and fully; and the vacuum ball valve is quickly opened and closed at least twice to blow off the phosphorus mixture adsorbed on the inner wall of the exhaust pipe; Step S5, exhaust and furnace opening operation.

[0021] It should be pointed out that before executing step S1 of this scheme, the crystal rod should be cooled for a certain time according to different feed amounts. For example, for a feed amount of 160kg, consider setting the cooling time to 7 hours to ensure that the internal temperature drops evenly and avoid thermal stress causing internal defects in the crystal rod. By precisely controlling the cooling time, the changes in the microstructure inside the crystal rod can also be reduced and the material properties can be improved. The cooling process also needs to monitor temperature changes to ensure that the target temperature range is reached within the specified time. For another example, for a feed amount of 200kg, consider extending the cooling time to 10 hours to accommodate the additional heat brought by the larger feed amount. Longer cooling times also help avoid lattice deformation or stress concentration caused by rapid cooling. At the same time, by extending the cooling time, the overall uniformity and stability of the crystal rod can be improved.

[0022] Step S1 and step S2 are both preparations before the inert gas replacement operation, and specifically consist of a crystal rod removal operation in step S1 and a high vacuum gauge isolation operation in step S2.

[0023] For step S1, it specifically considers quickly closing the upper furnace drum after taking out the crystal rod to ensure the stability of the furnace atmosphere and prevent combustion in the furnace. At the same time, the air entering the furnace should be reduced as much as possible during the closing of the upper furnace drum to improve the subsequent inert gas replacement efficiency. After taking out the crystal rod and closing the upper furnace drum, an airtightness check should be performed to ensure that the single crystal furnace is leak-free.

[0024] For step S2, first consider adding a needle valve at the bottom of the high vacuum gauge in the exhaust pipeline to avoid interference with the high vacuum gauge during the inert gas replacement process. In this way, when the isolation operation of the high vacuum gauge is carried out, the high vacuum gauge is isolated from the exhaust pipeline due to the closure of the isolation valve, protecting the high vacuum gauge from damage. At the same time, consider closing the needle valve at the bottom of the high vacuum gauge to further ensure that the high vacuum gauge is not disturbed during the inert gas replacement process. Of course, after this, all valve states should also be checked to ensure that the replacement process proceeds smoothly.

[0025] When performing the inert gas replacement operation, step S3 may mainly include inert gas flow and APC valve control, that is, including setting the initial inert gas flow, and realizing the two processes of inert gas flow and furnace pressure adjustment. Among them, the inert gas flow and APC valve control process mainly consider the initialization setting of the inert gas flow. For example, the inert gas flow is initially set to 50slm, the APC opening is set to 30 degrees, and the replacement process is started. Among them, the setting of the inert gas flow and APC opening needs to be adjusted according to the furnace volume and the replacement target. The initial flow setting needs to consider the balance between the replacement efficiency and the inert gas consumption.

[0026] When adjusting the inert gas flow and furnace pressure, consider adjusting the furnace pressure of the single crystal furnace by adjusting the inert gas flow, the opening of the APC valve and / or the manual valve to replace the oxygen in the single crystal furnace with the inert gas. Of course, in order to ensure the implementation of this operation, it is necessary to improve the exhaust pipeline by adding a manual valve in the early stage, that is, to add a manual valve in front of the main valve of the single crystal furnace exhaust pipeline to assist in adjusting the furnace pressure. Specifically, when performing inert gas replacement, it can be achieved in three ways: The first one is to consider achieving inert gas replacement only by opening the APC valve: specifically, consider initially setting the inert gas flow rate to 50 slm and the APC valve opening to 30 degrees to start the inert gas replacement process; adjust the inert gas flow rate to 50 slm and the APC valve opening to 30 degrees and maintain them for 10 minutes to ensure that the inert gas and air are fully replaced.

[0027] The second method is to consider achieving inert gas replacement by opening the APC valve and the manual valve: specifically, the inert gas flow rate is initially set to 50slm, the APC valve opening is set to 30 degrees, and the inert gas replacement process is started; the inert gas flow rate is adjusted to 40slm, the APC valve opening is set to 30 degrees, and the manual valve is adjusted to keep the furnace pressure at 20-25kPa for 10 minutes to allow the inert gas and air to be fully replaced.

[0028] The third method is to consider achieving inert gas replacement by opening the manual valve: specifically, consider setting the initial inert gas flow rate to 50slm, setting the APC valve opening to 30 degrees, and starting the inert gas replacement process; adjust the inert gas flow rate to 30slm, increase the manual valve opening to keep the furnace pressure at 20-25kPa, and maintain it for 10 minutes to allow the inert gas and air to be fully replaced.

[0029] In this way, according to the actual situation, such as the structure of the actual single crystal furnace exhaust pipeline, and the setting and installation of the valve, a suitable implementation method can be selected. Of course, in order to further ensure the thoroughness of the replacement of inert gas and air, it is also possible to consider implementing two or three of them in sequence. For example, after executing the operation of the first implementation method, further execute the operation of the second implementation method; or after executing the operation of the first implementation method, further execute the operation of the third implementation method; or after executing the operation of the second implementation method, further execute the operation of the third implementation method; or, execute the operation of the first implementation method, execute the operation of the second implementation method after executing it, and then further execute the operation of the third implementation method.

[0030] Step S4 is used to burn the phosphorus mixture in the pipeline, which can mainly include the operation of closing the inert gas and maintaining the furnace pressure, and the operation of the vacuum ball valve. Wherein, when the inert gas is closed and the furnace pressure is maintained, consider closing the inert gas supply first, then open the valve for putting air after opening the isolation valve, the opening of the APC valve is maintained at 30 degrees, and the opening of the manual valve is further increased so that the furnace pressure is maintained at 20-25kPa. Further, 7.5 hours can be maintained in this state to ensure that the atmosphere after replacement is stable. Of course, in order to ensure the stability of pressure, the furnace pressure change should be monitored in real time during the whole process, and the furnace pressure is maintained within the range of 20-25kPa by timely adjusting the opening of the manual valve.

[0031] Since the vacuum ball valve is usually the place where the phosphorus mixture is most likely to accumulate, and the phosphorus mixture adsorbed on the vacuum ball valve is often difficult to be burned and removed, based on this, this embodiment considers further performing the operation of opening and closing the vacuum ball valve six times at a preset time interval, so that the phosphorus mixture accumulated and adsorbed on the inner wall of the exhaust pipe can be blown off, and the phosphorus mixture is fully mixed with air, so that the phosphorus mixture can be fully burned.

[0032] Of course, it should be noted that the ball valve operation needs to be performed quickly and accurately, so that the adsorbed phosphorus mixture can be blown off by the instantaneous airflow impact at intervals. And the rapid switching operation can also avoid the backflow of gas and affect the gas replacement effect. In practice, the exhaust pipeline is composed of two branches. It is easy to understand that the vacuum ball valves on the two branches should be quickly switched on and off 6 times respectively. After the vacuum ball valve operation is completed, open the vacuum ball valve to maintain the continuity of the replacement process.

[0033] In addition, in order to reduce the phosphorus mixture adsorbed in the vacuum pipe, especially accumulated in the dead corner, in one embodiment, it is also possible to consider increasing the bending radius of each vacuum pipe, such as changing each bend of the pipe into an arc with a larger radius, so as to reduce the accumulation of the phosphorus mixture at the bend, and also facilitate the blowing off of the adsorbed phosphorus mixture by opening and closing the vacuum ball valve.

[0034] Finally, the exhaust and furnace opening operation of step S5 is performed. Specifically, consider first closing the APC valve, stopping the inert gas supply, and preparing for exhaust; then closing the manual valve, stopping the flow of gas, and preparing for furnace opening; finally, the furnace barrel can be opened after the pressure is reached.

[0035] During the implementation of this solution, the temperature of the pipeline can be measured by a temperature measuring gun to monitor the change of the pipeline temperature and determine the combustion state of the phosphorus mixture.

[0036] It should be noted that the inert gas mentioned in this scheme includes argon.

[0037] The modules or units in the device of the embodiment of the present invention can be combined, divided and deleted according to actual needs. The above disclosure is only the preferred embodiment of the present invention, and of course it cannot be used to limit the scope of the rights of the present invention. Those skilled in the art can understand that all or part of the processes of the above embodiment are implemented, and the equivalent changes made according to the claims of the present invention still fall within the scope of the invention.

Claims

1. A method for exhausting after pulling a heavily phosphorus-doped silicon single crystal, characterized in that: Before opening the isolation valve between the upper furnace drum and the lower furnace drum, the inert gas is used to replace the air in the upper furnace drum of the single crystal furnace by adjusting the flow rate of the inert gas and the opening of the APC valve or the manual valve used to balance and adjust the furnace pressure; and after opening the isolation valve between the upper furnace drum and the lower furnace drum, air is introduced into the single crystal furnace so that the red phosphorus in the phosphorus mixture in the exhaust pipe of the single crystal furnace burns slowly and fully after contacting with the air, and the phosphorus mixture adsorbed on the inner wall of the exhaust pipe is blown off by continuously switching the vacuum ball valve.

2. The exhaust method after pulling a heavily phosphorus-doped silicon single crystal according to claim 1, characterized in that: The exhaust method specifically includes: Step S1, pre-operation after the crystal ingot is taken out: close the isolation valve between the upper furnace drum and the lower furnace drum, and quickly close the upper furnace drum after the crystal ingot is taken out to ensure a stable atmosphere in the single crystal furnace; Step S2, high vacuum gauge isolation operation: close the needle valve at the bottom of the high vacuum gauge to ensure that the high vacuum gauge is not disturbed during the inert gas replacement process; wherein the needle valve is a valve added to the bottom of the high vacuum gauge in the exhaust pipeline, which is used to prevent the inert gas replacement process from interfering with the high vacuum gauge; Step S3, inert gas replacement operation: the furnace pressure of the single crystal furnace is regulated and controlled by adjusting the inert gas flow rate, the opening of the APC valve and / or the manual valve, so as to replace the air in the furnace drum of the single crystal furnace with the inert gas; wherein the manual valve is a manual valve added before the main valve of the exhaust pipeline of the single crystal furnace, which is used to assist in regulating the furnace pressure; Step S4, combustion operation of the phosphorus mixture in the exhaust pipe: after opening the isolation valve, introducing air into the single crystal furnace, and maintaining the furnace pressure of the single crystal furnace by adjusting the opening of the APC valve and the opening of the manual valve, so that the phosphorus mixture burns slowly and fully; and the vacuum ball valve is quickly opened and closed at least twice to blow off the phosphorus mixture adsorbed on the inner wall of the exhaust pipe; Step S5, exhaust and furnace opening operation.

3. The exhaust method after pulling a heavily phosphorus-doped silicon single crystal according to claim 2, characterized in that: In the step S1, after the crystal rod is taken out and the upper furnace drum is closed, an airtightness check is performed to ensure that the single crystal furnace has no leakage.

4. The exhaust method after pulling a heavily phosphorus-doped silicon single crystal according to claim 2, characterized in that: The step S3 specifically includes: The inert gas flow rate was initially set to 50±2slm, the APC valve opening was set to 30±0.5 degrees, and the inert gas replacement process was started; Adjust the inert gas flow rate to 50±2slm and the APC valve opening to 30±0.5 degrees, and maintain the first preset time.

5. The exhaust method after pulling a heavily phosphorus-doped silicon single crystal according to claim 2, characterized in that: The step S3 specifically includes: The inert gas flow rate is initially set to 50±2slm, the APC valve opening is set to 30±0.5 degrees, and the inert gas replacement process is started; The inert gas flow rate is adjusted to 40±2slm, the APC valve opening is adjusted to 30±0.5 degrees, and the manual valve is adjusted to keep the furnace pressure at 20-25kPa for the second preset time.

6. The exhaust method after pulling a heavily phosphorus-doped silicon single crystal according to claim 2, characterized in that: The step S3 specifically includes: The inert gas flow rate is initially set to 50±2slm, the APC valve opening is set to 30±0.5 degrees, and the inert gas replacement process is started; The inert gas flow rate is adjusted to 30±2slm, and the manual valve is adjusted to keep the furnace pressure at 20-25kPa for a third preset time period.

7. The exhaust method after pulling a heavily phosphorus-doped silicon single crystal according to claim 2, characterized in that: In step S4, after the isolation valve is opened, air is introduced into the single crystal furnace, and the furnace pressure of the single crystal furnace is maintained by adjusting the opening of the APC valve and the opening of the manual valve, including: Close the inert gas supply, open the valve for letting in air, keep the APC valve opening at 30±0.5 degrees, and increase the manual valve opening to maintain the furnace pressure at 20-25kPa; and, Maintaining a fourth preset time period under the condition; During the fourth preset time period, the furnace pressure change is monitored in real time, and the furnace pressure is maintained by adjusting the opening of the manual valve.

8. The exhaust method after pulling a heavily phosphorus-doped silicon single crystal according to claim 2, characterized in that: In step S4, the vacuum ball valve is rapidly opened and closed at least twice, comprising: The vacuum ball valve is opened and closed six times at preset time intervals to blow off the phosphorus mixture accumulated and adsorbed on the inner wall of the exhaust pipe, and the phosphorus mixture is burned after being fully contacted with air.

9. The exhaust method after pulling a heavily phosphorus-doped silicon single crystal according to claim 3, characterized in that: The step S5 comprises: Close the APC valve, stop the inert gas supply, and prepare for exhaust; Close the manual valve to stop the gas flow and prepare to start the furnace; Open the furnace after reaching normal pressure.

10. The exhaust method after pulling a heavily phosphorus-doped silicon single crystal according to any one of claims 1 to 9, characterized in that: The inert gas is argon.

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