A preparation method of a boron diffusion layer of a TOPCon cell

Abstract

The application discloses a preparation method of a boron diffusion layer of a TOPCon cell and belongs to the technical field of photovoltaic cell manufacturing. A silicon wafer is loaded into a tube diffusion furnace, and the pressure in the furnace is drawn from normal pressure to 600+ / -10 mbar; under the pressure, pressure stabilization leak detection, oxygen passing pretreatment, oxygen passing post-purging, segmented source passing and purging are sequentially performed to complete boron diffusion; then, boron propulsion and high-temperature wet oxygen oxidation are performed to grow a wet oxygen oxidation passivation layer; after cooling, the pressure is restored to normal pressure, and the silicon wafer is taken out. The pressure in the whole process is kept at 600+ / -10 mbar, and there is no pressure jump. The application controls the low pressure without jump reasonably, cooperates with the segmented source passing and intermediate purging, reduces the bearing stress of the quartz tube and inhibits the corrosion of the boron source, so that the quartz tube replacement cycle is more than 403 days, the service life is prolonged to 12-18 months, the energy consumption is reduced by more than 30%, and the application is suitable for mass production of N-type large-size silicon wafers.

Description

Technical Field

[0001] This invention relates to the field of solar cell manufacturing technology, and specifically to a method for preparing a boron diffusion layer in a TOPCon solar cell. Background Technology

[0002] In solar cell manufacturing, TOPCon (Tunneling Oxide Passivated Contact) technology has become one of the mainstream approaches in the photovoltaic industry due to its extremely high conversion efficiency potential. During the fabrication of TOPCon cells, boron diffusion is a key step in forming the P+ emitter or achieving effective substrate doping. To further improve doping quality and surface passivation, the industry commonly employs a process route combining boron diffusion and wet oxygen oxidation.

[0003] However, existing TOPCon boron diffusion wet oxygen processes generally operate in ultra-low pressure environments of 200 mbar or below, and are often accompanied by single-pass power supply without purging or two-stage pressure jump processes. This existing process has revealed serious technical shortcomings in actual large-scale mass production: First, in a high-temperature diffusion environment of around 850℃, the furnace tube is kept at an ultra-low pressure of ≤200mbar for a long time, which will cause a huge pressure difference between the inside and outside of the quartz tube, which can easily cause stress concentration in the structure.

[0004] Secondly, the existing two-stage pressure jump operation will cause the thermal and mechanical stress inside the tube to be unable to be released in a timely and stable manner, making the quartz tube at high temperature extremely prone to micro-cracks, or even serious furnace tube rupture accidents.

[0005] Furthermore, due to the lack of coordinated purging and flow field optimization in the low-pressure process, the concentration distribution of highly corrosive reactive gases such as BCl3 and wet oxygen in the furnace tube is difficult to achieve optimal balance, which exacerbates the chemical corrosion rate of the quartz tube wall (SiO2).

[0006] The combined effects of physical / mechanical stress and chemical corrosion result in an extremely short lifespan for quartz furnace tubes in existing mass production lines, with an average lifespan of only about 98 days. Frequent replacement of quartz furnace tubes not only severely impacts the uptime and production cycle of battery production lines but also leads to high equipment maintenance costs (a single replacement and maintenance can cost as much as 80,000-100,000 RMB), significantly hindering cost reduction and efficiency improvement in TOPCon battery manufacturing.

[0007] Therefore, the industry urgently needs to develop a new boron diffusion wet oxygen process to effectively reduce the high-temperature pressure burden and chemical corrosion rate of quartz tubes, release thermal stress, and thus significantly extend the service life of equipment and reduce the overall mass production cost, while ensuring the uniformity of sheet resistance and doping passivation effect of TOPCon cells. Summary of the Invention

[0008] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a method for preparing a boron diffusion layer for TOPCon batteries. This method aims to solve the problems of stress cracking and corrosion damage in quartz tubes through a reasonable pressure control and corrosion inhibition synergistic mechanism, significantly extending the service life of quartz tubes, while ensuring stable battery performance, reducing energy consumption and maintenance costs, and adapting to the needs of large-scale mass production of large-size silicon wafers.

[0009] The specific technical solution of the present invention is as follows: This invention provides a method for preparing a boron diffusion layer in a TOPCon battery, comprising the following steps: Step 1: Load the N-type monocrystalline silicon wafer into the tube diffusion furnace and pump the furnace pressure from atmospheric pressure to the core process pressure, which is 600±10 mbar. Step 2: Under the core process pressure, perform the following steps in sequence: pressure stabilization and leak detection, oxygen pretreatment, post-oxygen purging, segmented power supply and post-power supply purging, until the boron diffusion process is completed; Step 3: After completing the boron diffusion process, a boron propulsion process is performed under the core process pressure; Step 4: After completing the boron propulsion process, a high-temperature wet oxygen oxidation process is performed under the core process pressure to grow a wet oxygen oxidation passivation layer; Step 5: After completing the high-temperature wet oxidation process, a cooling process is performed under the core process pressure. After cooling, the pressure inside the furnace is raised from the core process pressure back to atmospheric pressure, and the silicon wafer is removed. Throughout the entire process from step two to step five, the core process pressure inside the furnace is maintained at 600±10mbar without any pressure fluctuations.

[0010] Furthermore, the segmented source described in step two includes a three-stage segmented source, specifically: First stage of boron source injection: Under the conditions of 820-830℃ and 600±10 mbar in temperature zones 1 to 6, BCl3 (100±10) sccm, nitrogen at the furnace door 1900-2100 sccm, DN26 800-7200 sccm, and SO2 430-470 sccm were injected for 180s to complete the first boron source injection. After the first source is introduced, purge: turn off BCl3 and SO2, increase the temperature from 820-830℃ to 830-840℃ in temperature zones 1 to 6, maintain the pressure at 600±10 mbar, introduce nitrogen into the furnace door at 1900-2100 sccm and DN26 at 800-7200 sccm for 80 seconds to remove boron source residue in the furnace; Second stage of boron source injection: Under the conditions of 830-840℃ and 600±10 mbar in temperature zones 1 to 6, BCl3 (100±10) sccm, nitrogen at the furnace door (1900-2100 sccm), DN26 (800-7200 sccm), and SO2 (430-470 sccm) are injected for 180s to complete the second boron source injection. Heating transition: Turn off BCl3 and SO2, raise the temperature from 830-840℃ to 840-850℃ in temperature zones 1 to 6, maintain the pressure at 600±10 mbar, and introduce nitrogen at 1900-2100 sccm and DN26 at 800-7200 sccm through the furnace door for 80 seconds; The third stage of boron source injection: Under the conditions of 840-850℃ and 600±10 mbar in temperature zones 1 to 6, BCl3 (100±10) sccm, nitrogen at the furnace door (1900-2100 sccm), DN26 (800-7200 sccm), and SO2 (430-470 sccm) are introduced for 150s to complete the third boron source injection. After the third source purging: turn off BCl3 and SO2, raise the temperature from 840-850℃ to 845-855℃ in temperature zones 1 to 6, maintain the pressure at 600±10 mbar, and introduce nitrogen into the furnace door at 1900-2100 sccm and DN26 at 800-7200 sccm for 180s to remove residual boron source in the furnace.

[0011] Further, the oxygen pretreatment step in step two is as follows: under the conditions of 820-830℃ and 600±10 mbar in temperature zones 1 to 6, nitrogen of 1400-1600 sccm, DN2 of 1900-2100 sccm, and SO2 of 1650-1790 sccm are introduced through the furnace door for 240s to complete the pre-oxidation of the silicon wafer surface.

[0012] Furthermore, the high-temperature wet oxidation process in step four includes: High-temperature humid oxygen oxidation first stage: Temperature zones 1 to 6 are heated from 885-895℃ to 990-1010℃, pressure is maintained at 600±10 mbar, H2O is introduced at 22000-23000 sccm, nitrogen at the furnace door is introduced at 2400-2600 sccm, time is 1200s; Second stage of high temperature and humid oxygen oxidation: maintain temperature zone 1 to temperature zone 6 at 990~1010℃, pressure at 600±10 mbar, introduce H2O at 22000~23000 sccm, introduce nitrogen at the furnace door at 2400~2600 sccm, for 2100s; The third stage of high-temperature humid oxygen oxidation: maintain temperature zones 1 to 6 at 990–1010℃ and pressure at 600±10 mbar, introduce H2O at 22000–23000 sccm, nitrogen at the furnace door at 2400–2600 sccm, and DN2 at 1900–2100 sccm for 1200s, and cumulatively grow an 80–100 nm humid oxygen oxidation passivation layer.

[0013] Furthermore, the boron propulsion process in step three includes: Boron propulsion first stage: Temperature zones 1 to 6 are heated from 845-855℃ to 885-895℃, pressure is maintained at 600±10mbar, and nitrogen is introduced through the furnace door at 450-550 sccm and DN26800-7200 sccm; The second stage of boron propulsion: maintain the temperature zone 1 to temperature zone 6 at 885-895℃ and the pressure at 600±10 mbar, and introduce nitrogen at 450-550 sccm and DN26800-7200 sccm through the furnace door.

[0014] Furthermore, before the pressure inside the furnace is drawn from atmospheric pressure to the core process pressure as described in step one, the process also includes boat loading and pressure extraction preparation steps: Boat loading: Temperature zones 1 to 6 are 790–810℃, pressure is 1050–1070 mbar, nitrogen is introduced into the furnace door at 900–1100 sccm and DN22 at 800–3200 sccm, and the silicon wafer boat is sent into the furnace tube. Preparation for pressure extraction: Maintain temperature zones 1 to 6 at 790–810℃ and pressure at 1050–1070 mbar, introduce nitrogen at 900–1100 sccm and DN22 at 800–3200 sccm through the furnace door to establish a stable environment.

[0015] Furthermore, the cooling process described in step five includes: First stage of cooling: Temperature zones 1 to 6 are cooled from 990-1010℃ to 890-910℃, pressure is maintained at 600±10mbar, H2O flow rate is reduced to 18500-19000 sccm, and nitrogen is introduced into the furnace door at 2400-2600 sccm and DN2 at 6000-6500 sccm. Second stage of cooling: Temperature zones 1 to 6 are cooled from 890-910℃ to 740-760℃, pressure is maintained at 600±10mbar, H2O is shut off, nitrogen is introduced through the furnace door at 2900-3100 sccm and DN2 at 9500-10500 sccm for 950-1050s.

[0016] Furthermore, after the pressure inside the furnace is raised from the core process pressure to atmospheric pressure in step five, a gas purging step is also included: maintaining temperature zones 1 to 6 at 740–760°C and pressure at 1050–1070 mbar, and introducing nitrogen at 900–1100 sccm and DN22800–3200 sccm through the furnace door to purge residual corrosive gases inside the furnace.

[0017] Furthermore, the tubular diffusion furnace is a 6-temperature zone tubular diffusion furnace with pressure closed-loop control function, which is suitable for mass production of N-type large-size monocrystalline silicon wafers.

[0018] Furthermore, the replacement cycle of the quartz tube in the method is more than 403 days, and the service life of the quartz tube is 12 to 18 months.

[0019] Compared with existing ultra-low pressure two-in-one processes, the present invention has the following significant advantages: 1. Quantitative improvement in lifespan: Through a reasonable low-pressure, non-jumping design of 600±10 mbar, the core pain points of the existing two-in-one process, namely high pressure under ultra-low pressure and pressure fluctuation under pressure jumps, are solved. The lifespan is increased from 6-9 months to 12-18 months, which is 2 times longer. The annual maintenance cost of a single unit is reduced from 50,000-70,000 yuan to 20,000-30,000 yuan. 2. Dual protection against quartz tube damage for enhanced stability: For the first time, dual protection is achieved through "reasonable low-pressure pressure to prevent bursting + removal of boron source residue to prevent corrosion". This not only solves the stress damage problem of quartz tubes, but also removes boron source residue, slows down the reaction rate of corrosive gases, reduces quartz tube damage, maintains stable mechanical properties, and significantly reduces equipment replacement and maintenance costs. 3. Stable battery yield and efficiency without fluctuations: While optimizing the protection of the quartz tube, the uniformity of boron diffusion is improved by gradient heating and segmented power supply. The oxide layer growth logic of the existing two-in-one process is not changed. The battery conversion efficiency and yield remain stable compared with the existing two-in-one process, without significant improvement or fluctuations. This avoids the impact of process optimization on the performance of mass-produced products and does not require adjustment of existing production process standards. 4. Reduce costs and increase efficiency, adapt to existing mass production: No new core equipment is needed. The existing equipment architecture and process flow of the two-in-one process can be directly used without changing the existing mass production plan. At the same time, the extra energy consumption of ultra-low pressure vacuuming is avoided, the overall energy consumption is reduced by more than 30%, and the process time is basically the same as the existing two-in-one process, taking into account both equipment protection and mass production economy. 5. More stable process operation and lower difficulty of operation: The pressure is controlled in a closed loop throughout the entire process and is always within the safe range of 600±10 mbar. There is no pressure jump, no need for complicated manual adjustment, and the process batch difference is small, which reduces the safety risk of quartz tube bursting. The operation is simple, reduces labor and safety protection costs, and is suitable for the process control needs of large-scale mass production. Attached Figure Description

[0020] Figure 1 This is a comparison chart of the furnace tube life variation trends between the conventional process and the process of the present invention in the embodiments of the present invention; Figure 2 This is a graph showing the trend of TOPCon battery warehousing yield and warehousing efficiency before and after process switching in an embodiment of the present invention. Detailed Implementation

[0021] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0022] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0023] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that excludes other embodiments. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall be followed. Where the manufacturers of reagents or instruments are not specified, they are all conventional products that can be purchased commercially.

[0024] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0025] Example 1 This embodiment provides a low-pressure co-optimized TOPCon boron diffusion wet oxygen process, based on an existing tubular diffusion furnace (with precise temperature control in 6 temperature zones and pressure closed-loop control function) and supporting gas pipelines. This embodiment uses N-type monocrystalline silicon wafers (182mm×182mm) as the processing object, and the core process pressure throughout the entire process is strictly controlled at 600±10 mbar, with no pressure jumps.

[0026] The specific process steps are as follows: 1. Production preparation Load the N-type monocrystalline silicon wafers into the quartz boat and confirm that the number, orientation, and spacing of the wafers meet the process requirements; check the pressure control module, gas pipeline, MFC, and temperature control accuracy of the tube furnace, and confirm that there are no residual impurities and particles in the furnace, and complete the pre-inspection of the equipment.

[0027] 2. Entering the boat The robotic arm delivers the silicon wafer boat into the furnace tube and closes the furnace door. The temperature in zones 1-6 is set to a constant 790-810℃, and the furnace pressure is maintained at atmospheric pressure of 1050-1070 mbar. Nitrogen is introduced into the furnace door at a rate of 900-1100 sccm and DN22 at a rate of 800-3200 sccm to ensure the silicon wafers are smoothly fed into the furnace and to avoid temperature shock.

[0028] 3. Preparation for pressure extraction Maintain a constant temperature of 790–810℃ and a normal pressure of 1050–1070 mbar in zones 1 to 6. Introduce nitrogen at 900–1100 sccm through the furnace door and 800–3200 sccm through DN22 to establish a stable temperature and gas environment.

[0029] 4. Core process pressure setting Temperature zones 1 to 6 are heated at a constant rate from 790 to 810°C to 805 to 815°C, and the furnace pressure is reduced from 1050 to 1070 mbar to the core process pressure of (600±10) mbar. Nitrogen is introduced into the furnace door at 900 to 1100 sccm and into DN2 at 4800 to 5200 sccm to complete the smooth transition to the low-pressure environment and avoid pressure differential impact on the quartz tube.

[0030] 5. Voltage stabilization and leak detection Maintain a constant temperature of 810~820℃ and a pressure of (600±10) mbar in zone 1-6 to confirm that there are no leaks in the furnace body, thus establishing a stable foundation for subsequent processes.

[0031] 6. Oxygenation pretreatment Temperature zones 1-6 are heated uniformly from 810 to 820℃ to 820 to 830℃, while the pressure inside the furnace is kept constant at (600±10) mabr. Nitrogen is introduced into the furnace door at a rate of 1400 to 1600 sccm, DN2 at 1900 to 2100 sccm, and SO2 at 1650 to 1790 sccm for 240 seconds to complete the pre-oxidation of the silicon wafer surface and provide a stable interface for boron diffusion.

[0032] 7. Purge after oxygenation Maintain a constant temperature of 820–830℃ and a pressure of 600±10 mbar in zones 1 to 6. Introduce nitrogen at 1900–2100 sccm through the furnace door and 800–3200 sccm through DN22. Perform a 50–70s purging action to remove residual oxygen and impurities from the furnace.

[0033] 8. First segmented source connection Maintain a constant temperature of 820–830℃ and a pressure of 600±10 mbar in temperature zones 1 to 6. Introduce BCl3 at (100±10) sccm, nitrogen at the furnace door at 1900–2100 sccm, DN26 at 800–7200 sccm, and SO2 at 430–470 sccm for 180s to complete the first boron source injection.

[0034] 9. Purge after the first source flow Temperature zones 1 to 6 are heated uniformly from 820–830℃ to 830–840℃, maintaining a pressure of 600±10 mbar. BCl3 and SO2 are shut off, and nitrogen is introduced through the furnace door at 1900–2100 sccm and DN26 at 800–7200 sccm for 80 seconds. This effectively removes residual boron source and B2O3 byproducts from the furnace and blocks corrosion pathways.

[0035] 10. Second segmented source connection Maintain a constant temperature of 830–840℃ and a pressure of 600±10 mbar in temperature zones 1 to 6. Introduce BCl3 at (100±10) sccm, nitrogen at the furnace door at 1900–2100 sccm, DN2 at 800–7200 sccm, and SO2 at 430–470 sccm for 180s to complete the second boron source injection and improve diffusion uniformity.

[0036] 11. Temperature transition Temperature zones 1 to 6 are heated at a constant rate from 830 to 840°C to 840 to 850°C, while maintaining a pressure of 600 ± 10 mbar. BCl3 and SO2 are shut off, and nitrogen is introduced through the furnace door at a rate of 1900 to 2100 sccm and DN26 at a rate of 800 to 7200 sccm for 80 seconds to establish the temperature conditions for the third power supply.

[0037] 12. Third segmented source connection Maintain a constant temperature of 840–850℃ and a pressure of 600±10 mbar in temperature zones 1 to 6. Introduce BCl3 (100±10) sccm, nitrogen at the furnace door (1900–2100 sccm), DN2 (800–7200 sccm), and SO2 (430–470 sccm) for 150 seconds to complete the third boron source injection and precisely control the sheet resistance of boron diffusion.

[0038] 13. Purging after the third source diversion Temperature zones 1 to 6 are heated uniformly from 840–850℃ to 845–855℃, with the furnace pressure maintained at 600±10 mbar. BCl3 and SO2 are shut off, and nitrogen is introduced through the furnace door at 1900–2100 sccm and DN26 at 800–7200 sccm for 180 seconds to effectively remove boron source residues in the furnace and complete corrosion protection during the boron diffusion stage.

[0039] 14. Boron Propulsion Stage 1 Temperature zones 1 to 6 are heated at a constant rate from 845 to 855°C to 885 to 895°C, while maintaining a pressure of 600 ± 10 mbar. Nitrogen is introduced through the furnace door at a rate of 450 to 550 sccm and DN26 at a rate of 800 to 7200 sccm to promote the directional diffusion of boron atoms into the silicon wafer and control the emitter junction depth.

[0040] 15. Boron-driven second stage Maintain a constant temperature of 885–895℃ and a pressure of 600±10 mbar in temperature zones 1 to 6, and introduce nitrogen at 450–550 sccm and DN26800–7200 sccm through the furnace door to further optimize the uniformity of boron diffusion and the consistency of junction depth.

[0041] 16. High-temperature and humid oxygen oxidation, first stage Temperature zones 1 to 6 are heated at a constant rate from 885 to 895°C to 990 to 1010°C, while the pressure inside the furnace is maintained at 600 ± 10 mbar. H2O (water vapor) is introduced at 22,000 to 23,000 sccm, and nitrogen at the furnace door at 2,400 to 2,600 sccm for 1,200 seconds, at which point the wet oxygen oxidation passivation layer begins to grow.

[0042] 17. High-temperature and humid oxygen oxidation, second stage Maintain a constant temperature of 990–1010℃ and a pressure of 600±10 mbar in temperature zones 1 to 6, maintain H2O at 22000–23000 sccm and nitrogen at the furnace door at 2400–2600 sccm for 2100 s to complete the oxide layer growth transition.

[0043] 18. High-temperature and humid oxygen oxidation, third stage Maintain a constant temperature of 990–1010℃ and a pressure of 600±10 mbar in temperature zones 1 to 6. Introduce 22000–23000 sccm of H2O, 2400–2600 sccm of nitrogen at the furnace door, and 11900–2100 sccm of DN2 for 1200s to grow a dense and uniform wet oxygen oxidation passivation layer of 80–100nm, ensuring the quality of interface passivation.

[0044] 19. Insulation after oxidation Maintain a constant temperature of 990–1010℃ and a pressure of 600±10 mbar in temperature zones 1 to 6, maintain H2O at 22000–23000 sccm and nitrogen at the furnace door at 2400–2600 sccm, and optimize the density and uniformity of the oxide layer.

[0045] 20. First stage of cooling Temperature zones 1 to 6 are cooled uniformly from 990–1010℃ to 890–910℃, maintaining a pressure of 600±10 mbar. The H2O flow rate is reduced to 18500–19000 sccm, and nitrogen is introduced into the furnace door at 2400–2600 sccm and DN2 at 6000–6500 sccm to steadily lower the furnace temperature and avoid thermal shock.

[0046] 21. Second stage of cooling Temperature zones 1 to 6 are cooled uniformly from 890–910℃ to 740–760℃, maintaining a pressure of 600±10 mbar. H2O is shut off, and nitrogen is introduced through the furnace door at 2900–3100 sccm and DN2 at 9500–10500 sccm. Cooling is then performed for 950–1050 seconds to further reduce the furnace temperature.

[0047] 22. Pressure Rebounds (Preparations Before Departure) Maintain a constant temperature of 740–760℃ in zones 1 to 6, and increase the furnace pressure from 600±10 mbar to 1050–1070 mbar atmospheric pressure. Introduce nitrogen at 2900–3100 sccm and DN27800–8200 sccm through the furnace door to complete the pressure and temperature preparations before unloading.

[0048] 23. Inflation and purging Maintain a constant temperature of 740–760℃ and a normal pressure of 1050–1070 mbar in zones 1 to 6. Introduce 900–1100 sccm of nitrogen through the furnace door and 800–3200 sccm of nitrogen through the DN22 furnace to effectively purge residual corrosive gases inside the furnace and protect the quartz tube.

[0049] 24. Get out of the boat Maintain the temperature of zones 1-6 at 740-760℃, maintain the pressure at 1050-1070 mbar (atmospheric pressure), introduce nitrogen into the furnace door at 1900-2100 sccm and DN2 at 900-1100 sccm, and then use a robotic arm to remove the silicon wafer boat to complete the entire process.

[0050] This embodiment performs production line statistics on the process. Figure 1 The bar chart shows a comparison of the quartz tube replacement cycle between the process of this invention and the existing ultra-low pressure two-in-one process. The results show that after switching processes on the same machine, the furnace tube replacement cycle increased from an average of 98 days to 403 days, the furnace tube life increased by more than 4 times, and the annual maintenance cost of a single unit decreased from 80,000 to 100,000 yuan to 20,000 to 30,000 yuan.

[0051] Figure 2The graph shows the statistical line graphs of battery yield and conversion efficiency before and after the process switching of this invention. The data shows that the production line yield and efficiency both increased slightly after the switching, with no obvious downward trend, indicating that this invention does not have a negative impact on battery performance while extending the life of the quartz tube.

[0052] Energy consumption and process efficiency optimization: No extra energy consumption is required for ultra-low pressure vacuuming, reducing overall energy consumption by more than 30%, and the entire process time is basically the same as the existing two-in-one process, which is suitable for mass production rhythm.

[0053] The above detailed description is a specific description of one of the feasible embodiments of the present invention. This embodiment is not intended to limit the patent scope of the present invention. All equivalent implementations or modifications that do not depart from the present invention should be included within the scope of the technical solution of the present invention.

[0054] It should be particularly noted that the various embodiments listed in this specification and accompanying drawings are intended to illustrate the technical solutions and advantages of the present invention, and not to limit the scope of protection of the present invention. Without departing from the core ideas and technical effects of the present invention, those skilled in the art can make any form of improvement, substitution, combination, or modification to the structural arrangement, process parameters, material selection, control logic, etc., of the described embodiments; any obvious changes based on the same concept should be considered equivalent solutions of the present invention and should be included within the scope of protection defined by the claims of the present invention. The actual scope of protection of the present invention is determined by the appended claims and should be correctly understood in conjunction with the specification and accompanying drawings.

Claims

1. A method for preparing a boron diffusion layer in a TOPCon battery, characterized in that, Includes the following steps: Step 1: Load the N-type monocrystalline silicon wafer into the tube diffusion furnace and pump the furnace pressure from atmospheric pressure to the core process pressure, which is 600±10 mbar. Step 2: Under the core process pressure, perform the following steps in sequence: pressure stabilization and leak detection, oxygen pretreatment, post-oxygen purging, segmented power supply and post-power supply purging, until the boron diffusion process is completed. Step 3: After completing the boron diffusion process, a boron propulsion process is performed under the core process pressure; Step 4: After completing the boron propulsion process, a high-temperature wet oxygen oxidation process is performed under the core process pressure to grow a wet oxygen oxidation passivation layer; Step 5: After completing the high-temperature wet oxidation process, a cooling process is performed under the core process pressure. After cooling, the pressure inside the furnace is raised from the core process pressure back to atmospheric pressure, and the silicon wafer is removed. Throughout the entire process from step two to step five, the core process pressure inside the furnace is maintained at 600±10 mbar without any pressure fluctuations.

2. The method for preparing the boron diffusion layer of the TOPCon battery according to claim 1, characterized in that, The segmented source described in step two includes three-stage segmented source construction, specifically: First stage of boron source injection: Under the conditions of 820-830℃ and 600±10 mbar in temperature zones 1 to 6, BCl3 (100±10) sccm, nitrogen at the furnace door 1900-2100 sccm, DN2 6800-7200 sccm, and SO2 430-470 sccm were injected for 180s to complete the first boron source injection. After the first source is introduced, purge: turn off BCl3 and SO2, increase the temperature from 820-830℃ to 830-840℃ in temperature zones 1 to 6, maintain the pressure at 600±10 mbar, introduce nitrogen into the furnace door at 1900-2100 sccm and DN2 at 6800-7200 sccm for 80s to remove boron source residue in the furnace; Second stage of boron source injection: Under the conditions of 830-840℃ and 600±10 mbar in temperature zones 1 to 6, BCl3 (100±10) sccm, nitrogen at the furnace door 1900-2100 sccm, DN2 6800-7200 sccm, and SO2 430-470 sccm are introduced for 180s to complete the second boron source injection; Heating transition: Turn off BCl3 and SO2, raise the temperature from 830-840℃ to 840-850℃ in temperature zones 1 to 6, maintain the pressure at 600±10 mbar, introduce nitrogen into the furnace door at 1900-2100 sccm and DN2 at 6800-7200 sccm for 80s; The third stage of boron source injection: Under the conditions of 840-850℃ and 600±10 mbar in temperature zones 1 to 6, BCl3 (100±10) sccm, nitrogen at the furnace door 1900-2100 sccm, DN2 6800-7200 sccm, and SO2 430-470 sccm were introduced for 150s to complete the third boron source injection. After the third source purging: shut off BCl3 and SO2, raise the temperature from 840-850℃ to 845-855℃ in temperature zones 1 to 6, maintain the pressure at 600±10 mbar, introduce nitrogen into the furnace door at 1900-2100 sccm and DN2 at 6800-7200 sccm for 180s to remove residual boron source in the furnace.

3. The method for preparing the boron diffusion layer of the TOPCon battery according to claim 1, characterized in that, The oxygen pretreatment step in step two is as follows: under the conditions of 820-830℃ and 600±10 mbar in temperature zones 1 to 6, nitrogen of 1400-1600 sccm, DN2 of 1900-2100 sccm and SO2 of 1650-1790 sccm are introduced through the furnace door for 240s to complete the pre-oxidation of the silicon wafer surface.

4. The method for preparing the boron diffusion layer of the TOPCon battery according to claim 1, characterized in that, The high-temperature wet oxidation process in step four includes: High-temperature humid oxygen oxidation first stage: Temperature zones 1 to 6 are heated from 885-895℃ to 990-1010℃, pressure is maintained at 600±10 mbar, H2O is introduced at 22000-23000 sccm, nitrogen at the furnace door is introduced at 2400-2600 sccm, time is 1200s; Second stage of high temperature and humid oxygen oxidation: maintain temperature zone 1 to temperature zone 6 at 990~1010℃, pressure at 600±10 mbar, introduce H2O2 at 2000~23000 sccm, introduce nitrogen at the furnace door at 2400~2600 sccm, for 2100s; The third stage of high-temperature humid oxygen oxidation: maintain temperature zones 1 to 6 at 990–1010℃ and pressure at 600±10 mbar, introduce H2O2 at 2000–23000 sccm, nitrogen at the furnace door at 2400–2600 sccm, and DN2 at 1900–2100 sccm for 1200s, and cumulatively grow an 80–100 nm humid oxygen oxidation passivation layer.

5. The method for preparing the boron diffusion layer of the TOPCon battery according to claim 1, characterized in that, The boron propulsion process in step three includes: Boron propulsion first stage: Temperature zones 1 to 6 are heated from 845-855℃ to 885-895℃, pressure is maintained at 600±10mbar, and nitrogen is introduced through the furnace door at 450-550 sccm and DN2 at 6800-7200 sccm; The second stage of boron propulsion: maintain the temperature zone 1 to temperature zone 6 at 885-895℃ and the pressure at 600±10 mbar, and introduce nitrogen at 450-550 sccm through the furnace door and 6800-7200 sccm through DN2.

6. The method for preparing the boron diffusion layer of the TOPCon battery according to claim 1, characterized in that, Before the pressure inside the furnace is drawn from atmospheric pressure to the core process pressure as described in step one, the process also includes boat loading and pressure extraction preparation steps: Boat loading: Temperature zones 1 to 6 are 790–810℃, pressure is 1050–1070 mbar, nitrogen is introduced into the furnace door at 900–1100 sccm and DN2 at 2800–3200 sccm, and the silicon wafer boat is sent into the furnace tube. Preparation for pressure extraction: Maintain temperature zones 1 to 6 at 790–810℃ and pressure at 1050–1070 mbar, introduce nitrogen at 900–1100 sccm through the furnace door and at 2800–3200 sccm through DN2 to establish a stable environment.

7. The method for preparing the boron diffusion layer of the TOPCon battery according to claim 1, characterized in that, The cooling process described in step five includes: First stage of cooling: Temperature zones 1 to 6 are cooled from 990-1010℃ to 890-910℃, pressure is maintained at 600±10mbar, H2O flow rate is reduced to 18500-19000 sccm, nitrogen is introduced into the furnace door at 2400-2600 sccm, and DN2 at 6000-6500 sccm; Second cooling stage: Temperature zones 1 to 6 are cooled from 890–910℃ to 740–760℃, pressure is maintained at 600±10 mbar, H2O is shut off, nitrogen is introduced through the furnace door at 2900–3100 sccm and DN2 at 9500–10500 sccm for 950–1050s.

8. The method for preparing the boron diffusion layer of the TOPCon battery according to claim 1, characterized in that, Step five, after raising the furnace pressure from the core process pressure back to atmospheric pressure, also includes a gas purging step: maintaining temperature zones 1 to 6 at 740–760°C and pressure at 1050–1070 mbar, introducing nitrogen at 900–1100 sccm through the furnace door and 2800–3200 sccm through DN2 to purge residual corrosive gases inside the furnace.

9. The method for preparing the boron diffusion layer of a TOPCon battery according to claim 1, characterized in that, The tubular diffusion furnace is a 6-temperature zone tubular diffusion furnace with pressure closed-loop control function, suitable for mass production of N-type large-size monocrystalline silicon wafers.

10. The method for preparing the boron diffusion layer of a TOPCon battery according to any one of claims 1 to 9, characterized in that, The replacement cycle of the quartz tube in the method is more than 403 days, and the service life of the quartz tube is 12 to 18 months.

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