LPCVD furnace tube pretreatment method and solar cell production method

Abstract

The invention relates to an LPCVD (low pressure chemical vapor deposition) furnace tube pretreatment method and a solar cell production method, and the pretreatment method divides a saturated furnace tube into two times, and correspondingly divides a purging furnace tube into two times, namely first saturation, first nitrogen purging, second saturation and second nitrogen purging. In the process, more undecomposed silane is generated after the first saturation, and most residual silane can be removed through the first nitrogen purging; and an oxygen braising process is used before secondary nitrogen purging, residual impurities in the furnace tube are further removed through reaction, and then the impurities in the furnace tube are thoroughly removed through secondary nitrogen purging. When the furnace tube treated by the method disclosed by the invention is used for production, the first boat airflow printing risk can be effectively avoided, so that the yield of TOPCon batteries is improved.

Description

Technical Field

[0001] The invention relates to the technical field of solar cells, and in particular to a LPCVD furnace tube pretreatment method and a solar cell production method. Background Art

[0002] In crystalline silicon solar cells, serious recombination exists in the metal-semiconductor contact area, which has become an important factor restricting the development of crystalline silicon solar cell efficiency. One of the biggest advantages of TOPCon solar cells is that the tunneling oxide layer and the doped polysilicon layer on the back constitute a tunneling oxide passivation contact structure (p-poly structure), which can significantly reduce the recombination of the metal contact area, while having good contact performance, which can greatly improve the efficiency of solar cells.

[0003] At present, one of the core processes of TOPCon cells is the LPCVD (low-pressure thermal chemical vapor deposition) process. The specific method is to send the silicon wafer into the LPCVD furnace tube through a carrier, and then introduce silane to deposit a layer of amorphous silicon on the surface of the silicon wafer. However, in the process of using the new furnace tube for amorphous silicon deposition, the furnace tube will be saturated by introducing a large amount of silane into the furnace tube to provide a stable environment for subsequent amorphous silicon deposition.

[0004] However, the silane in the saturated furnace tubes will not have time to decompose or will not be completely decomposed, and will be deposited in the furnace tubes. When the furnace tubes with this situation are used for production, the risk of first boat gas flow will occur, which will affect the quality of TOPCon batteries and reduce the yield rate of TOPCon batteries. Summary of the invention

[0005] Based on this, it is necessary to provide a LPCVD furnace tube pretreatment method to address the above problems, so as to eliminate the risk of first boat gas flow printing and improve the yield rate of TOPCon solar cells.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is:

[0007] A LPCVD furnace tube pretreatment method comprises: providing a LPCVD equipment furnace tube provided with a new air inlet pipe, injecting an empty paddle into the furnace tube, and performing leak detection and saturation purge on the furnace tube, wherein the saturation purge process comprises:

[0008] Saturating the furnace tube for the first time so that the tube wall of the furnace tube absorbs reactive silane;

[0009] Purging the furnace tube with nitrogen for the first time to clean the undecomposed silane gas in the furnace tube;

[0010] Saturating the furnace tube for the second time so that the tube wall of the furnace tube can fully absorb the reactive silane;

[0011] Performing a first vacuum pumping on the furnace tube to remove the silane gas in the furnace tube;

[0012] Blowing oxygen into the furnace tube to absorb residual impurities in the furnace tube through oxidation reaction;

[0013] The furnace tube is evacuated for the second time to remove oxygen in the furnace tube;

[0014] The furnace tube is purged with nitrogen for the second time to clean the undecomposed silane gas in the furnace tube.

[0015] In one embodiment, the second saturation time is shorter than the first saturation time.

[0016] In one embodiment, the pressure and nitrogen flow rate of the second nitrogen purge are greater than the pressure and nitrogen flow rate of the first nitrogen purge.

[0017] In one of the embodiments, the saturation time of the first saturation is 2000s-2500s, the silane flow rate in the middle of the furnace tube is 200sccm-400sccm, and the silane flow rate in the tail of the furnace tube is 600sccm-800sccm.

[0018] In one embodiment, the purge time of the first nitrogen purge is 1000s-1800s, the pressure in the tube is 100mTorr-300mTorr, the nitrogen flow rate in the middle of the furnace tube is 1000sccm-1200sccm, and the nitrogen flow rate in the tail of the furnace tube is 1000sccm-1200sccm.

[0019] In one of the embodiments, the saturation time of the second saturation is 500s-1000s, the silane flow rate in the middle of the furnace tube is 200sccm-400sccm, and the inlet silane flow rate at the rear of the furnace tube is 600sccm-800sccm.

[0020] In one embodiment, the furnace tube is suffocated with oxygen for 300s-600s, and the oxygen flow rate is 30000sccm.

[0021] In one embodiment, the purge time of the second nitrogen purge is 3000s-3500s, the pressure in the tube is 600mTorr-800mTorr, the nitrogen flow rate in the middle of the furnace tube is 2000sccm-3000sccm, and the nitrogen flow rate in the tail of the furnace tube is 2000sccm-3000sccm.

[0022] In one embodiment, after the second nitrogen purge, the method further comprises:

[0023] The furnace tube is evacuated for the third time to remove the residual gas in the furnace tube;

[0024] The furnace tube is vacuum-broken to make the pressure inside and outside the furnace tube the same.

[0025] A solar cell production method uses the LPCVD furnace tube treated by the pretreatment method to perform LPCVD operations.

[0026] The LPCVD furnace tube pretreatment method disclosed in the present invention divides the saturated furnace tube into two times, and the corresponding purging furnace tube is also divided into two times, namely the first saturation-the first nitrogen purge-the second saturation-the second nitrogen purge. In this process, there are many undecomposed silanes after the first saturation, and the first nitrogen purge can remove most of the residual silane; before the second nitrogen purge, an oxygen simmering process is used to further react the residual impurities in the furnace tube, and then the second nitrogen purge is used to thoroughly clean out the impurities in the furnace tube. When the furnace tube treated by the method disclosed in the present invention is used for production, the risk of first boat gas flow printing can be effectively avoided, thereby improving the yield rate of TOPCon batteries.

[0027] In addition, the first saturation time is long, and the amount of silane introduced is large, which can preliminarily change the surface state of the furnace tube and its air inlet pipe, while the second saturation time is short, and the amount of silane introduced is small, so the surface state of the furnace tube and its air inlet pipe can be carefully repaired, making the surface state of the furnace tube and its air inlet pipe more perfect. At the same time, since the pressure and nitrogen flow of the second nitrogen purge are greater than the pressure and nitrogen flow of the first nitrogen purge, that is, different purge speeds are achieved through different pressures and different nitrogen flows, especially the high pressure and high flow of the second nitrogen purge, which can quickly and thoroughly clean out impurities in the furnace tube. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a flow chart of the LPCVD furnace tube pretreatment method of the present invention. DETAILED DESCRIPTION

[0029] For ease of understanding of the present invention, the present invention will be described in more detail below. However, it should be understood that the present invention can be implemented in many different forms and is not limited to the embodiments or examples described herein. On the contrary, the purpose of providing these embodiments or examples is to make the understanding of the disclosure of the present invention more thorough and comprehensive.

[0030] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by those skilled in the art of the present invention. The terms used herein in the specification of the present invention are only for the purpose of describing specific implementation methods or embodiments, and are not intended to limit the present invention. The optional scope of the term "and / or" used herein includes any one of two or more related listed items, and also includes any and all combinations of related listed items, and the combinations include any two related listed items, any more related listed items, or all related listed items.

[0031] like Figure 1 As shown, an embodiment of the present invention discloses a LPCVD furnace tube pretreatment method, comprising: providing a LPCVD equipment furnace tube provided with a new air inlet pipe, injecting an empty paddle into the furnace tube, and performing leak detection and saturation purge on the furnace tube, wherein the saturation purge process comprises:

[0032] Saturating the furnace tube for the first time so that the tube wall of the furnace tube absorbs reactive silane;

[0033] Purging the furnace tube with nitrogen for the first time to clean the undecomposed silane gas in the furnace tube;

[0034] Saturating the furnace tube for the second time so that the tube wall of the furnace tube can fully absorb the reactive silane;

[0035] The furnace tube is evacuated for the first time to remove the silane gas in the furnace tube;

[0036] Blowing oxygen into the furnace tube to absorb residual impurities in the furnace tube through oxidation reaction;

[0037] The furnace tube is evacuated for the second time to remove oxygen in the furnace tube;

[0038] The furnace tube is purged with nitrogen for the second time to clean the undecomposed silane gas in the furnace tube.

[0039] The LPCVD furnace tube pretreatment method disclosed in this embodiment divides the saturated furnace tube into two times, and the corresponding purging furnace tube is also divided into two times, namely the first saturation-the first nitrogen purge-the second saturation-the second nitrogen purge. In this process, there are many undecomposed silanes after the first saturation, and the first nitrogen purge can remove most of the residual silane; before the second nitrogen purge, an oxygen simmering process is used to further react the residual impurities in the furnace tube, and then the second nitrogen purge is used to thoroughly clean out the impurities in the furnace tube. When the furnace tube treated by the method disclosed in the present invention is used for production, the risk of first boat gas printing can be effectively avoided, thereby improving the yield rate of TOPCon batteries.

[0040] Another embodiment of the present invention discloses another specific LPCVD furnace tube pretreatment method, the method comprising:

[0041] A new air intake pipe is installed, wherein a small air leakage hole is arranged on the air intake pipe.

[0042] Use compressed air to manually blow for 3 minutes to remove dust particles on the inner wall of the intake pipe, and then wipe the dust particles on the outer wall of the pipe with a dust-free cloth soaked in alcohol.

[0043] Install the air inlet pipe and assemble the LPCVD furnace tube completely. The air vent holes on the wall of the air inlet pipe should be installed facing the wall, and should not blow directly on the silicon wafer to avoid affecting the deposition of amorphous silicon.

[0044] Drive the empty paddle into the furnace tube where the new intake tube is installed.

[0045] Evacuate the furnace tube to a low pressure state.

[0046] Leak detection, check the furnace tube leakage tightness to prevent chemical gas leakage.

[0047] Purging: At a temperature of 600°C, nitrogen gas at a flow rate of 1000sccm is introduced into the middle and rear inlet pipes of the furnace tube for about 800s-1200s to purge small particles of impurities on the wall of the inlet pipe.

[0048] Evacuate the furnace tube to remove any residual nitrogen and small particles of impurities.

[0049] The furnace tube is saturated for the first time so that the tube wall of the furnace tube absorbs the reaction silane. The saturation time of the first saturation is 2000s-2500s, the silane flow rate in the middle of the furnace tube is 200sccm-400sccm, and the silane flow rate in the tail of the furnace tube is 600sccm-800sccm.

[0050] The furnace tube is purged with nitrogen for the first time to clean up the undecomposed silane gas in the furnace tube. The purging time of the first nitrogen purging is 1000s-1800s, the pressure in the tube is 100mTorr-300mTorr, the nitrogen flow rate in the middle of the furnace tube is 1000sccm-1200sccm, and the nitrogen flow rate in the tail of the furnace tube is 1000sccm-1200sccm.

[0051] The furnace tube is saturated for a second time, and the time of the second saturation is shorter than the time of the first saturation, so that the tube wall of the furnace tube fully absorbs the reactive silane. The saturation time of the second saturation is 500s-1000s, the silane flow rate in the middle of the furnace tube is 200sccm-400sccm, and the silane flow rate in the tail of the furnace tube is 600sccm-800sccm.

[0052] The furnace tube is evacuated for the first time to remove the silane gas in the furnace tube.

[0053] The furnace tube is suffocated with oxygen to absorb the residual impurities in the furnace tube through oxidation reaction. The suffocation time is 300s-600s, and the oxygen flow rate is 30000sccm.

[0054] The furnace tube is evacuated for the second time to remove the oxygen in the furnace tube.

[0055] The furnace tube is purged with nitrogen for the second time, and the pressure and nitrogen flow rate of the second nitrogen purge are greater than the pressure and nitrogen flow rate of the first nitrogen purge, so as to clean the undecomposed silane gas in the furnace tube. The purge time of the second nitrogen purge is 3000s-3500s, the pressure in the tube is 600mTorr-800mTorr, the nitrogen flow rate in the middle of the furnace tube is 2000sccm-3000sccm, and the nitrogen flow rate in the tail of the furnace tube is 2000sccm-3000sccm.

[0056] In another embodiment, after the second nitrogen purge is completed, the following steps are further included:

[0057] The furnace tube is evacuated for the third time to remove the residual gas in the furnace tube;

[0058] The furnace tube is broken to make the pressure inside and outside the furnace tube the same. Specifically, 10000-20000 sccm of nitrogen can be filled to keep the pressure inside and outside the furnace tube consistent, in preparation for unloading the boat.

[0059] Finally, the boat trip ended.

[0060] The LPCVD furnace tube pretreatment method disclosed in the present invention divides the saturated furnace tube into two times, and the corresponding purging furnace tube is also divided into two times, namely the first saturation-the first nitrogen purge-the second saturation-the second nitrogen purge. In this process, there are many undecomposed silanes after the first saturation, and the first nitrogen purge can remove most of the residual silane; before the second nitrogen purge, an oxygen simmering process is used to further react the residual impurities in the furnace tube, and then the second nitrogen purge is used to thoroughly clean out the impurities in the furnace tube. When the furnace tube treated by the method disclosed in the present invention is used for production, the risk of first boat gas flow printing can be effectively avoided, thereby improving the yield rate of TOPCon batteries.

[0061] In addition, the first saturation time is long, and the amount of silane introduced is large, which can preliminarily change the surface state of the furnace tube and its air inlet pipe, while the second saturation time is short, and the amount of silane introduced is small, so the surface state of the furnace tube and its air inlet pipe can be carefully repaired, making the surface state of the furnace tube and its air inlet pipe more perfect. At the same time, since the pressure and nitrogen flow of the second nitrogen purge are greater than the pressure and nitrogen flow of the first nitrogen purge, that is, different purge speeds are achieved through different pressures and different nitrogen flows, especially the high pressure and high flow of the second nitrogen purge, which can quickly and thoroughly clean out impurities in the furnace tube.

[0062] Yet another embodiment of the present invention discloses a method for producing solar cells, which utilizes an LPCVD furnace tube that has been treated by the pretreatment method described in any of the above embodiments to perform LPCVD operations.

[0063] In another embodiment, a method for producing a solar cell is disclosed in more detail, including:

[0064] Pretreatment of LPCVD furnace tubes:

[0065] A new air intake pipe is installed, wherein a small air leakage hole is arranged on the air intake pipe.

[0066] Use compressed air to manually blow for 3 minutes to remove dust particles on the inner wall of the intake pipe, and then wipe the dust particles on the outer wall of the pipe with a dust-free cloth soaked in alcohol.

[0067] Install the air inlet pipe and assemble the LPCVD furnace tube completely. The air vent holes on the wall of the air inlet pipe should be installed facing the wall, and should not blow directly on the silicon wafer to avoid affecting the deposition of amorphous silicon.

[0068] Drive the empty paddle into the furnace tube where the new intake tube is installed.

[0069] Evacuate the furnace tube to a low pressure state.

[0070] Leak detection, check the furnace tube leakage tightness to prevent chemical gas leakage.

[0071] Purging: At a temperature of 600°C, nitrogen gas at a flow rate of 1000sccm is introduced into the middle and rear inlet pipes of the furnace tube for about 800s-1200s to purge small particles of impurities on the wall of the inlet pipe.

[0072] Evacuate the furnace tube to remove any residual nitrogen and small particles of impurities.

[0073] The furnace tube is saturated for the first time so that the tube wall of the furnace tube absorbs the reaction silane. The saturation time of the first saturation is 2000s-2500s, the silane flow rate in the middle of the furnace tube is 200sccm-400sccm, and the silane flow rate in the tail of the furnace tube is 600sccm-800sccm.

[0074] The furnace tube is purged with nitrogen for the first time to clean up the undecomposed silane gas in the furnace tube. The purging time of the first nitrogen purging is 1000s-1800s, the pressure in the tube is 100mTorr-300mTorr, the nitrogen flow rate in the middle of the furnace tube is 1000sccm-1200sccm, and the nitrogen flow rate in the tail of the furnace tube is 1000sccm-1200sccm.

[0075] The furnace tube is saturated for a second time, and the time of the second saturation is shorter than the time of the first saturation, so that the tube wall of the furnace tube fully absorbs the reactive silane. The saturation time of the second saturation is 500s-1000s, the silane flow rate in the middle of the furnace tube is 200sccm-400sccm, and the silane flow rate in the tail of the furnace tube is 600sccm-800sccm.

[0076] The furnace tube is evacuated for the first time to remove the silane gas in the furnace tube.

[0077] The furnace tube is suffocated with oxygen to absorb the residual impurities in the furnace tube through oxidation reaction. The suffocation time is 300s-600s, and the oxygen flow rate is 30000sccm.

[0078] The furnace tube is evacuated for the second time to remove the oxygen in the furnace tube.

[0079] The furnace tube is purged with nitrogen for the second time, and the pressure and nitrogen flow rate of the second nitrogen purge are greater than the pressure and nitrogen flow rate of the first nitrogen purge, so as to clean the undecomposed silane gas in the furnace tube. The purge time of the second nitrogen purge is 3000s-3500s, the pressure in the tube is 600mTorr-800mTorr, the nitrogen flow rate in the middle of the furnace tube is 2000sccm-3000sccm, and the nitrogen flow rate in the tail of the furnace tube is 2000sccm-3000sccm.

[0080] The furnace tube is evacuated for the third time to remove the residual gas in the furnace tube.

[0081] The furnace tube is vacuumed and filled with 10000-20000 sccm nitrogen to make the pressure inside and outside the furnace tube the same.

[0082] The boat is unloaded and the pretreatment of the LPCVD furnace tube is completed.

[0083] Normal production:

[0084] The silicon wafers or substrates that need to undergo the LPCVD process are sent into the pre-treated LPCVD furnace tube for LPCVD operation.

[0085] Check air flow marks and test film thickness:

[0086] Select a small boat in each temperature zone in the entire furnace tube, and select one piece each at the top, middle and bottom of each boat to check the airflow print on the front and back sides and test the film thickness.

[0087] The solar cell production method described in this embodiment can be applied to TOPcon structure cells, PERC cells and other solar cells using the LPCVD process.

[0088] The embodiment of the present invention takes the production of TOPCon batteries as an example to describe and analyze the method disclosed in the present invention in detail.

[0089] Embodiment 1:

[0090] Pretreatment of LPCVD furnace tubes:

[0091] Put a new air inlet pipe online, blow it manually with compressed air for 3 minutes, and wipe the outer wall of the pipe with a dust-free cloth with alcohol.

[0092] When installing the air inlet pipe, the air vent holes on the pipe wall should be installed facing the pipe wall. Do not blow directly on the silicon wafer to avoid affecting the deposition of amorphous silicon.

[0093] Evacuate the furnace tube to a low pressure state.

[0094] Leak detection, check the furnace tube leakage tightness to prevent chemical gas leakage.

[0095] Purging: At a temperature of 600°C, nitrogen gas is introduced into the middle and tail inlet pipes of the furnace tube at a flow rate of 1000 sccm for about 800 seconds to purge small particles of impurities on the wall of the inlet pipe.

[0096] Evacuate the furnace tube to remove any residual nitrogen and small particles of impurities.

[0097] The furnace tube is saturated for the first time. This saturation can also be called large saturation. The saturation time is 2500s. The silane flow rate is 400sccm in the furnace inlet pipe and 600sccm in the furnace tail inlet pipe. The stainless steel inlet pipe wall fully absorbs the reactive silane to change the surface state of the inlet pipe.

[0098] The furnace tube is purged with nitrogen for the first time, which can also be called the first low-pressure and low-flow nitrogen purge, with a purge time of 1000s, a pressure of 100mTorr in the tube, a nitrogen flow rate of 1000sccm in the inlet pipe in the furnace, and a nitrogen flow rate of 1000sccm in the inlet pipe at the tail of the furnace. The low pressure in the tube and the high pumping speed of the pump speed up the gas flow rate and clean up the undecomposed silane gas in the inlet pipe and the wall of the furnace tube.

[0099] The furnace tube is saturated for the second time. This saturation is also called small saturation. The saturation time is 1000s. The silane flow rate is 400sccm in the air inlet pipe in the middle of the furnace tube and 600sccm in the air inlet pipe at the tail of the furnace tube. Finally, the saturation effect required by the air inlet pipe is achieved.

[0100] The furnace tube is evacuated for the first time to completely remove the silane gas in the furnace tube in preparation for the next step of passing oxygen.

[0101] The furnace tube is suffocated with oxygen, and oxygen with a flow rate of 30,000 sccm is introduced into the furnace tube for 600 seconds, so that the residual impurities on the furnace tube and the wall of the air inlet pipe after saturation are absorbed through oxygen reaction.

[0102] The furnace tube is evacuated for the second time to remove all oxygen from the furnace tube, in preparation for the next step of nitrogen purge of the furnace tube.

[0103] The furnace tube is purged with nitrogen for the second time, and the nitrogen flow rate of the second nitrogen purge is relatively large. The purge time is 3000s, the pressure in the tube is 600mTorr, and the nitrogen flow rate is 2000sccm in the furnace inlet pipe and 2000sccm in the furnace tail inlet pipe. Excess nitrogen thoroughly cleans the furnace tube and the inlet pipe of the silane that has not been completely decomposed.

[0104] Evacuate the furnace to remove the residual gas in the furnace tube.

[0105] Break the vacuum and fill in 20,000 sccm of nitrogen to keep the pressure inside and outside the furnace tube consistent, in preparation for leaving the boat.

[0106] Out on the boat, end.

[0107] Normal production:

[0108] The silicon wafers that have been processed by the alkaline polishing process are sent into the pre-treated LPCVD furnace tube for LPCVD operation.

[0109] Check air flow marks and test film thickness:

[0110] Select a small boat from each temperature zone in the entire furnace tube, and select one piece each from the upper, middle and lower parts of each boat to check the airflow marks on the front and back sides and test the film thickness.

[0111] Comparative Example 1:

[0112] Pretreatment of LPCVD furnace tubes:

[0113] Put a new air inlet pipe online, blow it manually with compressed air for 3 minutes, and wipe the outer wall of the pipe with a dust-free cloth with alcohol.

[0114] When installing the air inlet pipe, the air vent holes on the pipe wall should be installed facing the pipe wall. Do not blow directly on the silicon wafer to avoid affecting the deposition of amorphous silicon.

[0115] Evacuate the furnace tube to a low pressure state.

[0116] Leak detection, check the furnace tube leakage tightness to prevent chemical gas leakage.

[0117] Purging: At a temperature of 600°C, nitrogen gas with a flow rate of 1000sccm is introduced into the middle and rear inlet pipes of the furnace tube for about 800s to purge small particles of impurities on the wall of the inlet pipe.

[0118] Evacuate the furnace tube to remove any residual nitrogen and small particles of impurities.

[0119] The furnace tube was saturated for 3500 seconds, with a silane flow rate of 400 sccm in the furnace and 600 sccm at the furnace tail.

[0120] The furnace tube was purged with nitrogen at a pressure of 600 mTorr and a purging time of 4000 s. The nitrogen flow rate was 2000 sccm in the furnace and 2000 sccm at the tail of the furnace.

[0121] Evacuate the chamber to remove any remaining gas.

[0122] Break the vacuum and fill in 20,000 sccm of nitrogen to keep the pressure inside and outside the furnace tube consistent, in preparation for leaving the boat.

[0123] Out on the boat, end.

[0124] Normal production:

[0125] The silicon wafers that have been processed by the alkaline polishing process are sent into the pre-treated LPCVD furnace tube for LPCVD operation.

[0126] Check air flow marks and test film thickness:

[0127] Select a small boat from each temperature zone in the entire furnace tube, and select one piece each from the upper, middle and lower parts of each boat to check the airflow marks on the front and back sides and test the film thickness.

[0128] Compared with Example 1, this comparative example changes the 2-step saturation and 2-step purge into the same 1-step purge and 1-step saturation as in the prior art. According to long-term tracking, the production line still has a 10% probability of airflow printing in the first boat produced after the intake pipe is replaced.

[0129] Comparative Example 2:

[0130] Pretreatment of LPCVD furnace tubes:

[0131] Put a new air inlet pipe online, blow it manually with compressed air for 3 minutes, and wipe the outer wall of the pipe with a dust-free cloth with alcohol.

[0132] When installing the air inlet pipe, the air vent holes on the pipe wall should be installed facing the pipe wall. Do not blow directly on the silicon wafer to avoid affecting the deposition of amorphous silicon.

[0133] Evacuate the furnace tube to a low pressure state.

[0134] Leak detection, check the furnace tube leakage tightness to prevent chemical gas leakage.

[0135] Purging: At a temperature of 600°C, nitrogen gas is introduced into the middle and tail inlet pipes of the furnace tube at a flow rate of 1000 sccm for about 800 seconds to purge small particles of impurities on the wall of the inlet pipe.

[0136] Evacuate the furnace tube to remove any residual nitrogen and small particles of impurities.

[0137] The furnace tube was saturated for the first time. The saturation time was 2500s, and the silane flow rate was 400sccm in the furnace inlet pipe and 600sccm in the furnace tail inlet pipe, so that the stainless steel inlet pipe wall fully absorbed the reactive silane to change the surface state of the inlet pipe.

[0138] The furnace tube was purged with nitrogen for the first time, with a purging time of 1000s, a pressure of 100mTorr in the tube, a nitrogen flow rate of 1000sccm in the inlet pipe in the furnace, and a nitrogen flow rate of 1000sccm in the inlet pipe at the tail of the furnace. The low pressure in the tube and the high pumping speed of the pump accelerated the gas flow rate and cleaned the undecomposed silane gas in the inlet pipe and the tube wall of the furnace tube.

[0139] The furnace tube was saturated for the second time. The saturation time was 1000s, and the silane flow rate was 400sccm in the air inlet pipe in the middle of the furnace tube and 600sccm in the air inlet pipe at the tail of the furnace tube. Finally, the required saturation effect of the air inlet pipe was achieved.

[0140] The furnace tube is evacuated for the first time to completely remove the silane gas in the furnace tube.

[0141] The furnace tube was purged with nitrogen for the second time. The purging time was 3000s, the pressure in the tube was 600mTorr, the nitrogen flow rate was 2000sccm in the furnace inlet pipe, and 2000sccm in the furnace tail inlet pipe. Excess nitrogen was used to thoroughly clean the undecomposed silane in the furnace tube and the inlet pipe.

[0142] Evacuate the chamber to remove any remaining gas.

[0143] Break the vacuum and fill in 20,000 sccm of nitrogen to keep the pressure inside and outside the furnace tube consistent, in preparation for leaving the boat.

[0144] Out on the boat, end.

[0145] Normal production:

[0146] The silicon wafers that have been processed by the alkaline polishing process are sent into the pre-treated LPCVD furnace tube for LPCVD operation.

[0147] Check air flow marks and test film thickness:

[0148] Select a small boat from each temperature zone in the entire furnace tube, and select one piece each from the upper, middle and lower parts of each boat to check the airflow marks on the front and back sides and test the film thickness.

[0149] Compared with Example 1, the oxygen blanching step is eliminated in this comparative example. According to long-term tracking, the production line still has a 6% probability of causing airflow printing in the first boat produced after the air intake pipe is replaced.

[0150] Comparative Example 3:

[0151] Pretreatment of LPCVD furnace tubes:

[0152] Put a new air inlet pipe online, blow it manually with compressed air for 3 minutes, and wipe the outer wall of the pipe with a dust-free cloth with alcohol.

[0153] When installing the air inlet pipe, the air vent holes on the pipe wall should be installed facing the pipe wall. Do not blow directly on the silicon wafer to avoid affecting the deposition of amorphous silicon.

[0154] Evacuate the furnace tube to a low pressure state.

[0155] Leak detection, check the furnace tube leakage tightness to prevent chemical gas leakage.

[0156] Purging: At a temperature of 600°C, nitrogen gas is introduced into the middle and tail inlet pipes of the furnace tube at a flow rate of 1000 sccm for about 800 seconds to purge small particles of impurities on the wall of the inlet pipe.

[0157] Evacuate the furnace tube to remove any residual nitrogen and small particles of impurities.

[0158] The furnace tube was saturated for the first time. The saturation time was 2500s, and the silane flow rate was 400sccm in the furnace inlet pipe and 600sccm in the furnace tail inlet pipe, so that the stainless steel inlet pipe wall fully absorbed the reactive silane to change the surface state of the inlet pipe.

[0159] The furnace tube was purged with nitrogen for the first time, with a purging time of 1000s, a pressure of 100mTorr in the tube, a nitrogen flow rate of 1000sccm in the inlet pipe in the furnace, and a nitrogen flow rate of 1000sccm in the inlet pipe at the tail of the furnace. The low pressure in the tube and the high pumping speed of the pump accelerated the gas flow rate and cleaned the undecomposed silane gas in the inlet pipe and the tube wall of the furnace tube.

[0160] The furnace tube was saturated for the second time. The saturation time was 1000s, and the silane flow rate was 400sccm in the air inlet pipe in the middle of the furnace tube and 600sccm in the air inlet pipe at the tail of the furnace tube. Finally, the required saturation effect of the air inlet pipe was achieved.

[0161] The furnace tube is evacuated for the first time to completely remove the silane gas in the furnace tube in preparation for the next step of passing oxygen.

[0162] The furnace tube is suffocated with oxygen, and oxygen with a flow rate of 30,000 sccm is introduced into the furnace tube for 600 seconds, so that the residual impurities on the furnace tube and the wall of the air inlet pipe after saturation are absorbed by oxygen reaction.

[0163] The furnace tube is evacuated for the second time to remove all oxygen from the furnace tube, in preparation for the next step of nitrogen purge of the furnace tube.

[0164] The furnace tube was purged with nitrogen for the second time. The purging time was 2000s, the pressure in the tube was 600mTorr, the nitrogen flow rate was 2000sccm in the furnace inlet pipe, and 2000sccm in the furnace tail inlet pipe. Excess nitrogen was used to thoroughly clean the undecomposed silane in the furnace tube and the inlet pipe.

[0165] Evacuate the chamber to remove any remaining gas.

[0166] Break the vacuum, fill with 20000sccm nitrogen, keep the pressure inside and outside the furnace tube consistent, and prepare for the boat to leave.

[0167] Out on the boat, end.

[0168] Normal production:

[0169] The silicon wafers that have been processed by the alkaline polishing process are sent into the pre-treated LPCVD furnace tube for LPCVD operation.

[0170] Check air flow marks and test film thickness:

[0171] Select a small boat from each temperature zone in the entire furnace tube, and select one piece each from the upper, middle and lower parts of each boat to check the airflow marks on the front and back sides and test the film thickness.

[0172] Compared with Example 1, the purge time of the second nitrogen purge in this comparative example is reduced from 3000 s to 2000 s.

[0173] After long-term tracking, it was found that there is still a 4% probability of air flow marks on the first boat produced after the intake pipe is replaced.

[0174] Table 1 is a comparison table of the probability of gas flow printing in the LPCVD process under various methods after long-term tracking:

[0175] Table 1

[0176]

[0177] It can be seen that the LPCVD furnace tube pretreatment method disclosed in the present invention divides the saturated furnace tube into two times, and the corresponding purging furnace tube is also divided into two times, and the oxygen simmering process is used before the second nitrogen purge. The first saturation time is long, and the amount of silane introduced is large, which can preliminarily change the surface state of the furnace tube and its air inlet pipe, while the second saturation time is short, and the amount of silane introduced is small, so the surface state of the furnace tube and its air inlet pipe can be carefully repaired, so that the surface state of the furnace tube and its air inlet pipe is more perfect. At the same time, since the pressure and nitrogen flow rate of the second nitrogen purge are greater than the pressure and nitrogen flow rate of the first nitrogen purge, that is, different purge speeds are achieved through different pressures and different nitrogen flow rates, especially the high pressure and high flow rate of the second nitrogen purge, which can quickly and thoroughly clean out the impurities in the furnace tube. When using the LPCVD furnace tube pretreated by this method to produce Topcon batteries, the probability of airflow printing is the lowest, especially compared with the prior art, the probability of airflow printing is significantly reduced, which means that the yield rate of Topcon batteries is significantly increased.

[0178] The technical features of the above-mentioned embodiments can be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification. The "first" and "second" mentioned in the text are only for distinction and are not intended to limit the content of the present invention.

[0179] The above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A LPCVD furnace tube pretreatment method, comprising: A LPCVD equipment furnace tube provided with a new air inlet pipe is provided, an empty paddle is driven into the furnace tube, and the furnace tube is leak tested and saturated purged, wherein the saturated purging process includes: Saturating the furnace tube for the first time so that the tube wall of the furnace tube absorbs reactive silane; Performing a first nitrogen purge on the furnace tube to clean the undecomposed silane gas in the furnace tube; Saturating the furnace tube for the second time so that the tube wall of the furnace tube can fully absorb the reactive silane; The furnace tube is evacuated for the first time to remove the silane gas in the furnace tube; Blowing oxygen into the furnace tube to absorb residual impurities in the furnace tube through an oxidation reaction; The furnace tube is evacuated for the second time to remove oxygen in the furnace tube; The furnace tube is purged with nitrogen for the second time to clean the undecomposed silane gas in the furnace tube.

2. The pretreatment method according to claim 1, characterized in that: The second saturation time is shorter than the first saturation time.

3. The pretreatment method according to claim 1, characterized in that: The pressure and nitrogen flow rate of the second nitrogen purge are greater than the pressure and nitrogen flow rate of the first nitrogen purge.

4. The pretreatment method according to claim 1, characterized in that: The saturation time of the first saturation is 2000s-2500s, the silane flow rate in the middle of the furnace tube is 200sccm-400sccm, and the silane flow rate in the tail of the furnace tube is 600sccm-800sccm.

5. The pretreatment method according to claim 1, characterized in that: The purge time of the first nitrogen purge is 1000s-1800s, the pressure in the tube is 100mTorr-300mTorr, the nitrogen flow rate in the middle of the furnace tube is 1000sccm-1200sccm, and the nitrogen flow rate at the tail of the furnace tube is 1000sccm-1200sccm.

6. The pretreatment method according to claim 1, characterized in that: The saturation time of the second saturation is 500s-1000s, the silane flow rate in the middle of the furnace tube is 200sccm-400sccm, and the inlet silane flow rate at the tail of the furnace tube is 600sccm-800sccm.

7. The pretreatment method according to claim 1, characterized in that: The furnace tube is suffocated with oxygen for 300s-600s, and the oxygen flow rate is 30000sccm.

8. The pretreatment method according to claim 1, characterized in that: The purge time of the second nitrogen purge is 3000s-3500s, the pressure in the tube is 600mTorr-800mTorr, the nitrogen flow rate in the middle of the furnace tube is 2000sccm-3000sccm, and the nitrogen flow rate at the tail of the furnace tube is 2000sccm-3000sccm.

9. The pretreatment method according to claim 1, characterized in that: After the second nitrogen purge, it also includes: The furnace tube is evacuated for the third time to remove the residual gas in the furnace tube; The furnace tube is vacuum-broken to make the pressure inside and outside the furnace tube the same.

10. A method for producing a solar cell, characterized in that: LPCVD operation is carried out using the LPCVD furnace tube treated by the pretreatment method described in any one of claims 1 to 9.

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