PE-poly processing method and TOPCon battery

Abstract

The invention discloses a PE-poly processing method and a TOPCon battery, and the processing method comprises the steps: feeding a silicon wafer after alkali polishing into a reaction chamber, introducing a reaction gas into the reaction chamber, inducing glow discharge in the reaction chamber by using a square wave power supply to construct a low-temperature plasma, and sequentially preparing a first tunneling oxide layer, a first phosphorus-doped amorphous silicon layer, a second tunneling oxide layer and a second phosphorus-doped amorphous silicon layer on the surface of the silicon wafer, wherein the phosphorus content of the second phosphorus-doped amorphous silicon layer is greater than that of the first phosphorus-doped amorphous silicon layer. According to the PE-poly processing method, the square-wave power supply is used, so that stable and continuous glow discharge is maintained in the reaction chamber due to the characteristics that the stable voltage level is kept for a long time in the period of the square-wave power supply, the switching time of the voltage direction is short and the like, and the generation of poly dust is effectively inhibited; and the first tunneling oxide layer, the first phosphorus-doped amorphous silicon layer, the second tunneling oxide layer and the second phosphorus-doped amorphous silicon layer are prepared on the silicon wafer in batches, so that the battery piece with higher yield and better electrical performance efficiency is obtained.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of photovoltaic cells, in particular to a PE-poly processing method and a TOPCon cell. BACKGROUND

[0002] TOPCon cells (Tunnel Oxide Passivating Contact cells) introduce an ultrathin tunnel oxide layer and a polysilicon layer on the back of the cell, effectively reducing interface recombination loss, improving open-circuit voltage and fill factor of the cell, and thus improving the photoelectric conversion efficiency of the cell. Preparing a TOPCon cell generally requires selecting a silicon wafer with a specified size, and then performing a series of processes such as texturing, boron diffusion, SE, oxidation, BSG removal, alkali etching, PE-poly deposition, PSG removal, RCA cleaning, ALD positive film coating, back film coating, screen printing, sintering, light injection, laser sintering, and testing. Among them, PE-poly is the abbreviation of PECVD (Plasma Enhanced Chemical Vapor Deposition) and poly (Polycrystalline), and the PE-poly deposition process is mainly used to prepare a phosphorus-doped polysilicon layer. The PE-poly process generally relies on a PECVD machine to implement. This process uses low-temperature plasma as an energy source to heat the silicon wafer placed in a graphite boat to a predetermined temperature, and then generates a tunnel oxide layer and a phosphorus-doped amorphous silicon layer on the surface of the silicon wafer. After high-temperature annealing, the phosphorus-doped amorphous silicon layer is converted into a phosphorus-doped polysilicon layer.

[0003] The existing PE-poly deposition process is susceptible to poly dust during implementation due to factors such as frequent switching of reaction conditions in the process, poor stability of the reaction environment, etc. The poly dust falls on the cell wafer, and the cell wafer contaminated by the poly dust is transferred to the subsequent processing process and processed into a cell wafer. The EL detection map of the finished cell wafer is darker than that of the normal cell wafer not contaminated by poly dust, there is a large area of irregular black spots in the cell, and the cell efficiency decreases significantly. Therefore, it is a technical problem that needs to be solved by those skilled in the art to improve the existing PE-poly deposition process and reduce the dust generated during the PE-poly deposition process. SUMMARY

[0004] The main purpose of the present application is to provide a PE-poly processing method that can effectively inhibit the generation of poly dust in the PE-poly process.

[0005] To achieve the above object, the application provides a PE-poly processing method, which comprises the following steps: sending a silicon wafer after alkali etching into a reaction chamber, introducing a reaction gas into the reaction chamber, using a square wave power source to induce glow discharge in the reaction chamber to construct a low-temperature plasma, and sequentially preparing a first tunneling oxide layer, a first phosphorus-doped amorphous silicon layer, a second tunneling oxide layer and a second phosphorus-doped amorphous silicon layer on the surface of the silicon wafer, wherein the phosphorus content of the second phosphorus-doped amorphous silicon layer is greater than that of the first phosphorus-doped amorphous silicon layer.

[0006] Optionally, the processing method comprises the following steps.

[0007] S1: sending a silicon wafer after alkali etching into a reaction chamber;

[0008] S2: heating the reaction chamber to increase the temperature of the silicon wafer to a preset temperature;

[0009] S3: introducing a nitrous oxide gas into the reaction chamber, using a square wave power source to induce glow discharge in the reaction chamber, and preparing a first tunneling oxide layer on the surface of the silicon wafer;

[0010] S4: introducing a mixed gas mixed by silane, hydrogen and phosphine into the reaction chamber, using a square wave power source to induce glow discharge in the reaction chamber, and preparing a first phosphorus-doped amorphous silicon layer on the first tunneling oxide layer;

[0011] S5: introducing a nitrous oxide gas into the reaction chamber, using a square wave power source to induce glow discharge in the reaction chamber, and preparing a second tunneling oxide layer on the first phosphorus-doped amorphous silicon layer;

[0012] S6: introducing a mixed gas mixed by silane, hydrogen and phosphine into the reaction chamber, using a square wave power source to induce glow discharge in the reaction chamber, and preparing a second phosphorus-doped amorphous silicon layer on the second tunneling oxide layer;

[0013] S7: using a square wave power source to induce glow discharge in the reaction chamber to prepare a mask layer on the second phosphorus-doped amorphous silicon layer;

[0014] S8: purging the silicon wafer, vacuumizing the reaction chamber, and sending the prepared silicon wafer out of the reaction chamber.

[0015] Optionally, S2 specifically comprises the following steps: setting a constant temperature heater and an auxiliary heater in the reaction chamber, the constant temperature heater is used for heating the silicon wafer, the constant temperature heater continuously operates to increase the temperature of the silicon wafer and keep it in the range of 425-435 DEG C; the auxiliary heater is used for heating the environment in the reaction chamber and a carrier carrying the silicon wafer, when the carrier carrying the silicon wafer enters the reaction chamber, the auxiliary heater starts to operate to increase the temperature of the carrier carrying the silicon wafer; when the temperature of the carrier carrying the silicon wafer increases to the range of 460-480 DEG C or the carrier carrying the silicon wafer leaves the reaction chamber, the auxiliary heater stops.

[0016] Optionally, S2 is specifically: at least one constant temperature heater and at least one auxiliary heater are arranged in the reaction chamber, the constant temperature heater keeps the current silicon wafer at 425-435℃ for 450s and then keeps the current silicon wafer at 425-435℃ for 300s; the auxiliary heater keeps the current silicon wafer and its surrounding environment at 430℃ for 400s and then keeps the current silicon wafer and its surrounding environment at 420℃ for 300s.

[0017] Optionally, S3 is specifically: nitrous oxide gas is introduced into the reaction chamber, the pressure in the reaction chamber is controlled to be 1800mtorr, the power of the square wave power source is controlled to be 14700-15000W, the frequency of the power source is controlled to be 40KHz, the duty cycle of the power source is controlled to be 1:80, the glow discharge is excited in the reaction chamber to construct the low-temperature plasma, and the running time of the square wave power source is controlled to be 69-92s, so that the first tunneling oxide layer with a thickness of 1-1.5nm is prepared on the surface of the silicon wafer.

[0018] Optionally, S4 is specifically: a mixed gas composed of silane, hydrogen and phosphine is introduced into the reaction chamber, the volume ratio of silane, hydrogen and phosphine in the mixed gas is controlled to be in the range of 10:32:1.1 to 10:38:1.1, the pressure in the reaction chamber is controlled to be 2800-3050mtorr, the power of the square wave power source is adjusted to be 14500W-15000W, the frequency of the power source is controlled to be 40KHz, the duty cycle of the power source is controlled to be in the range of 1:10 to 1:12, the glow discharge is excited in the reaction chamber to construct the low-temperature plasma, and the running time of the square wave power source is controlled to be 85-110s, so that the first phosphorus-doped amorphous silicon layer is prepared on the first tunneling oxide layer.

[0019] Optionally, S5 is specifically: nitrous oxide gas is introduced into the reaction chamber, the pressure in the reaction chamber is controlled to be 1800-2200mtorr, the power of the square wave power source is adjusted to be 14000-15000W, the frequency of the power source is controlled to be 40KHz, the duty cycle of the power source is controlled to be 1:30, the glow discharge is excited in the reaction chamber to construct the low-temperature plasma, and the running time of the square wave power source is controlled to be 35-45s, so that the second tunneling oxide layer with a thickness of 1-1.5nm is prepared on the first tunneling oxide layer.

[0020] Optionally, S6 is specifically: introducing a mixed gas mixed by silane, hydrogen and phosphine into the reaction chamber, controlling the volume ratio of silane, hydrogen and phosphine in the mixed gas to be in the range of 10:32:3.0 to 10:34:3.0, controlling the pressure of the reaction chamber to be in the range of 3000-3050mtorr, adjusting the square wave power to be 14500W-15000W, the power frequency to be 40KHz, and the power duty cycle to be in the range of 1:10 to 1:12, exciting glow discharge and constructing low-temperature plasma in the reaction chamber, and the operation time of the square wave power being in the range of 415-455s, to prepare the second phosphorus-doped amorphous silicon layer on the second tunneling oxide layer.

[0021] Optionally, S7 is specifically: introducing a mixed gas mixed by silane and nitrogen dioxide into the reaction chamber, controlling the volume ratio of silane and nitrogen dioxide in the mixed gas to be 1:4.3, controlling the pressure of the reaction chamber to be 1750mtorr, adjusting the square wave power to be 15000W-15500W, the power frequency to be 40KHz, and the power duty cycle to be in the range of 1:17.6 to 1:20, exciting glow discharge and constructing low-temperature plasma in the reaction chamber, and the operation time of the square wave power being in the range of 60-116s, to prepare the mask layer on the second phosphorus-doped amorphous silicon layer.

[0022] In the present application, a TOPCon cell is also provided, which comprises a poly layer prepared by the PE-poly processing method as described above.

[0023] The PE-poly processing method of the present application has the following advantages: by using a square wave power source, the PE-poly processing method of the present application maintains stable and continuous glow discharge in the reaction chamber by keeping stable voltage level for a long time in the square wave power cycle and short switching time of voltage direction, effectively inhibits the generation of poly dust, and obtains a cell sheet with higher yield and better electrical performance efficiency by preparing the first tunneling oxide layer, the first phosphorus-doped amorphous silicon layer, the second tunneling oxide layer and the second phosphorus-doped amorphous silicon layer on the silicon wafer in batches. BRIEF DESCRIPTION OF DRAWINGS

[0024] The present application will be described in detail below with reference to specific embodiments and drawings, in which:

[0025] Figure 1 The method flowchart of the PE-poly processing method provided in the present application. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical scheme and advantages of the present application clearer, the present application will be described in detail below with reference to the drawings and examples. It should be understood that the following specific examples are only used to explain the present application and do not limit the present application.

[0027] In the process of PE-poly, the silicon wafer is loaded on a graphite boat, the graphite boat is sent into the reaction chamber together with the silicon wafer, the silicon wafer is heated to a predetermined temperature, the reaction gas is introduced into the reaction chamber, and the low-temperature plasma is formed by discharging. The low-temperature plasma is used as an energy source to react with the silicon wafer to form an ultra-thin tunnel oxide layer, and a solid phosphorus-doped amorphous silicon film is further formed on the surface of the silicon wafer. After subsequent high-temperature annealing, the phosphorus-doped amorphous silicon layer is converted into a phosphorus-doped polysilicon layer.

[0028] In the present application, a PE-poly processing method is provided, which comprises the following steps: introducing the silicon wafer after alkali etching into a reaction chamber, introducing a reaction gas into the reaction chamber, and using a square wave power source to induce glow discharge in the reaction chamber to form a low-temperature plasma. A first tunnel oxide layer, a first phosphorus-doped amorphous silicon layer, a second tunnel oxide layer, and a second phosphorus-doped amorphous silicon layer are sequentially prepared on the surface of the silicon wafer. The phosphorus content of the second phosphorus-doped amorphous silicon layer is greater than that of the first phosphorus-doped amorphous silicon layer. In the present embodiment, a square wave power source is used. Compared with using a sine wave power source, the alternating current output by the square wave power source will present a waveform state of a forward stable high level-reversing-a reverse stable high level in a complete cycle. The reversing process of the alternating current from the forward stable high level to the reverse stable high level is extremely short, and compared with the stable voltage state, the voltage change is easy to produce poly dust in the reaction chamber. Using the square wave power source, the reaction chamber is in a stable peak voltage platform environment most of the time. The square wave power source induces stable, continuous, and smooth glow discharge in the reaction chamber and forms a low-temperature plasma. Since the alternating current output by the square wave power source is at a stable peak level most of the time, the voltage amplitude is maintained stable in a half cycle, and the switching time between the forward voltage and the reverse voltage is extremely short. By controlling the working frequency, duty cycle, and working power of the square wave power source, arc discharge or spark discharge in the reaction chamber can be effectively prevented, a stable and continuous glow discharge state in the reaction chamber can be maintained, the reaction process can be prevented from being damaged by intense flashing, and poly dust production can be inhibited. At the same time, the PE-poly processing method provided in the present embodiment sequentially prepares a first tunnel oxide layer, a first phosphorus-doped amorphous silicon layer, a second tunnel oxide layer, and a second phosphorus-doped amorphous silicon layer on the silicon wafer, and maintains the phosphorus content of the second phosphorus-doped amorphous silicon layer greater than that of the first phosphorus-doped amorphous silicon layer. This can ensure that a second phosphorus-doped amorphous silicon layer with sufficient thickness and sufficient phosphorus content is finally obtained.

[0029] Embodiment 1: Square wave power source process

[0030] In the present embodiment, a PE-poly processing method is provided, which comprises the following steps:

[0031] S10: Put the silicon wafer after alkali etching into a graphite boat; construct a reaction chamber with a quartz tube; the reaction chamber is provided with a constant temperature heater for heating the silicon wafer and an auxiliary heater; the constant temperature heater is continuously operated;

[0032] S11: Put the graphite boat loaded with the silicon wafer into the reaction chamber by a silicon carbide paddle; when the silicon carbide paddle puts the graphite boat loaded with the silicon wafer into the reaction chamber, the auxiliary heater starts to operate to increase the temperature of the carrier carrying the silicon wafer;

[0033] S12: Take the graphite boat entering the reaction chamber as the time starting point; keep the constant temperature heater at constant temperature for 800 s to increase and maintain the temperature of the silicon wafer in the range of 425-435℃; continuously heat the auxiliary heater for 600 s to increase the temperature of the graphite boat to the range of 460-480℃;

[0034] S13: The reaction temperature is the same as step S12; control the temperature of the silicon wafer in the range of 425-435℃; introduce nitrous oxide gas into the reaction chamber at a rate of 10000 sccm; control the pressure in the reaction chamber to be 1800mtorr; set the power of the square wave power supply to be 14700-15000W, the frequency of the power supply to be 40KHz, and the duty cycle of the power supply to be 1:80; excite glow discharge and construct low-temperature plasma in the reaction chamber; set the operation time of the square wave power supply to be 72-92s; and prepare a first tunneling oxide layer with a thickness of 1-1.5nm on the surface of the silicon wafer;

[0035] S14: The reaction temperature is the same as step S12; control the temperature of the silicon wafer in the range of 425-435℃; introduce a mixed gas composed of silane, hydrogen and phosphine into the reaction chamber; control the volume ratio of silane, hydrogen and phosphine in the mixed gas to be 10:32:1.1; the pressure in the reaction chamber is 2800mtorr; adjust the power of the square wave power supply to be 14500W-15000W, the frequency of the power supply to be 40KHz, and the duty cycle of the power supply to be 1:10; excite glow discharge and construct low-temperature plasma in the reaction chamber; and prepare a first phosphorus-doped amorphous silicon layer on the first tunneling oxide layer.

[0036] S15: The reaction temperature is the same as step S12; control the temperature of the silicon wafer in the range of 425-435℃; introduce nitrous oxide gas into the reaction chamber at a rate of 10000 sccm; control the pressure in the reaction chamber to be 1800mtorr; adjust the power of the square wave power supply to be 15000W, the frequency of the power supply to be 40KHz, and the duty cycle of the power supply to be 1:30; excite glow discharge and construct low-temperature plasma in the reaction chamber; and prepare a second tunneling oxide layer with a thickness of 1-1.5nm on the first tunneling oxide layer.

[0037] S16: The temperature of the silicon wafer is controlled in the range of 425-435 DEG C, a mixed gas of silane, hydrogen and phosphine is introduced into the reaction chamber, the volume ratio of silane, hydrogen and phosphine in the mixed gas is controlled to be 10:32:3.0, the pressure in the reaction chamber is controlled to be 3000mtorr, the power of the square wave power supply is adjusted to be 14500-15000W, the frequency of the power supply is 40KHz, the duty cycle of the power supply is 1:10, the glow discharge is excited in the reaction chamber to form a low temperature plasma, and the running time of the square wave power supply is in the range of 415-455s, so that the second phosphorus-doped amorphous silicon layer is prepared on the second tunneling oxide layer.

[0038] S17: A mixed gas of silane and nitrogen dioxide is introduced into the reaction chamber, the volume ratio of silane and nitrogen dioxide in the mixed gas is controlled to be 1:4.3, the pressure in the reaction chamber is controlled to be 1750mtorr, the power of the square wave power supply is adjusted to be 15000-15500W, the frequency of the power supply is 40KHz, the duty cycle of the power supply is 1:20, the glow discharge is excited in the reaction chamber to form a low temperature plasma, and the running time of the square wave power supply is in the range of 60-80s, so that the mask layer is prepared on the second phosphorus-doped amorphous silicon layer.

[0039] S18: The silicon wafer is blown by nitrogen, the reaction chamber is vacuumized, the nitrogen back pressure is recharged into the reaction chamber, the graphite boat is removed from the reaction chamber, and the silicon wafer is pressed out of the boat.

[0040] In the present application, a TOPCon cell is also provided, which comprises a poly layer prepared by the PE-poly processing method as described above.

[0041] The PE-poly processing using the sine wave power supply is easily affected by poly dust, and the specific embodiment one provided in the present embodiment uses the square wave power supply. The implementation cases of using the sine wave power supply and the square wave power supply in the specific embodiment one are tracked and compared, three groups of comparison experiments are set, the sine wave power supply is used in comparison group 1, comparison group 2 and comparison group 3, and the square wave power supply is used in experimental group 1, experimental group 2 and experimental group 3. The EL contamination ratio of the poly layer obtained after the implementation process is detected, and the EL contamination ratio data is shown in Table 1 as follows:

[0042]

[0043] (Table 1, the table shows the EL contamination ratio data of the poly layer obtained by using the sine wave power supply and the square wave power supply in the specific embodiment, EL refers to Electroluminescence, an electroluminescence imaging technology)

[0044] As shown in Table I, in the first verification, the EL dirt ratio of the poly layer obtained by the experimental group 1 using the square wave power supply process is reduced by 0.14% than that of the poly layer obtained by the comparative group 1 using the sine wave power supply; in the second verification, the EL dirt ratio of the poly layer obtained by the experimental group 2 using the square wave power supply process is reduced by 0.15% than that of the poly layer obtained by the comparative group 2 using the sine wave power supply; in the third verification, the EL dirt ratio of the poly layer obtained by the experimental group 3 using the square wave power supply process is reduced by 0.15% than that of the poly layer obtained by the comparative group 3 using the sine wave power supply. Obviously, from the data, replacing the sine wave power supply with the square wave power supply can inhibit the generation of poly dust to a certain extent.

[0045] The electrical performance parameters of the poly layers prepared in the above three groups of comparative experiments are tracked, and the electrical performance of the poly layers obtained after the implementation process is detected, and the electrical performance test results are shown in Table II as follows:

[0046]

[0047] (Table II, the table shows the electrical performance test data of the poly layers obtained by using the sine wave power supply and the square wave power supply in the specific embodiment, in the table, Eta refers to the photoelectric conversion efficiency, Uoc refers to the open circuit voltage, Isc refers to the short circuit current, FF refers to the fill factor, Rs refers to the series resistance, Rsh refers to the parallel resistance, and Irev2 refers to the leakage current)

[0048] As shown in Table II, in the first verification, the electrical performance efficiency of the poly layer obtained by the comparative group 1 using the sine wave power supply process is 0.059% lower than that of the poly layer obtained by the experimental group 1 using the square wave power supply in the specific embodiment; in the second verification, the electrical performance efficiency of the poly layer obtained by the comparative group 2 using the sine wave power supply process is 0.036% lower than that of the poly layer obtained by the experimental group 2 using the square wave power supply in the specific embodiment; in the third verification, the electrical performance efficiency of the poly layer obtained by the comparative group 3 using the sine wave power supply process is 0.044% lower than that of the poly layer obtained by the experimental group 3 using the square wave power supply in the specific embodiment. It can be seen that replacing the square wave power supply has a certain influence on the electrical performance efficiency of the poly layer, and the electrical performance efficiency of the poly layer is lost to a certain extent.

[0049] Specific embodiment two: square wave power supply process two

[0050] S20: loading the silicon wafer after alkali etching into a graphite boat; constructing a reaction chamber with a quartz tube; setting a constant temperature heater and an auxiliary heater in the reaction chamber, the constant temperature heater is used for heating the silicon wafer, and the constant temperature heater is continuously operated;

[0051] S21: A graphite boat loaded with silicon wafers is sent into the reaction chamber by a silicon carbide paddle, and when the silicon carbide paddle enters the reaction chamber with the graphite boat loaded with silicon wafers, the auxiliary heater starts to operate to raise the temperature of the carrier carrying the silicon wafers;

[0052] S22: The graphite boat enters the reaction chamber as the time starting point, and after the constant temperature heater maintains constant temperature heating for 400 s, it maintains constant temperature heating at 425-435°C for 300 s to raise the temperature of the silicon wafers and keep it in the range of 425-435°C; the auxiliary heater maintains 430°C auxiliary heating for 400 s around the current silicon wafer station and its surrounding environment, and then maintains 420°C auxiliary heating for 300 s to raise the temperature of the graphite boat to the range of 460-480°C;

[0053] S23: The reaction temperature is the same as step S22, the temperature of the silicon wafers is controlled in the range of 425-435°C, the nitrous oxide gas is introduced into the reaction chamber at a rate of 10000 sccm, the pressure in the reaction chamber is controlled at 1800mtorr, the power of the square wave power supply is controlled at 14700-15000W, the frequency of the power supply is controlled at 40KHz, and the duty cycle of the power supply is controlled at 1:80. A glow discharge is excited in the reaction chamber to form a low-temperature plasma, and the running time of the square wave power supply is controlled at 69-89s. A first tunneling oxide layer with a thickness of 1-1.5nm is prepared on the surface of the silicon wafer.

[0054] S24: The reaction temperature is the same as step S22, the temperature of the silicon wafers is controlled in the range of 425-435°C, a mixed gas composed of silane, hydrogen and phosphine is introduced into the reaction chamber, the volume ratio of silane, hydrogen and phosphine in the mixed gas is controlled at 10:38:1.1, the pressure in the reaction chamber is controlled at 3050mtorr, the power of the square wave power supply is adjusted to 14500-15000W, the frequency of the power supply is 40KHz, and the duty cycle of the power supply is 1:12. A glow discharge is excited in the reaction chamber to form a low-temperature plasma, and the running time of the square wave power supply is 90-110s. A first phosphorus-doped amorphous silicon layer is prepared on the first tunneling oxide layer.

[0055] S25: The reaction temperature is the same as step S22, the temperature of the silicon wafers is controlled in the range of 425-435°C, the nitrous oxide gas is introduced into the reaction chamber at a rate of 10000 sccm, the pressure in the reaction chamber is controlled at 2200mtorr, the power of the square wave power supply is adjusted to 14000-15000W, the frequency of the power supply is 40KHz, and the duty cycle of the power supply is 1:30. A glow discharge is excited in the reaction chamber to form a low-temperature plasma, and the running time of the square wave power supply is 23-43s. A second tunneling oxide layer with a thickness of 1-1.5nm is prepared on the first tunneling oxide layer.

[0056] S26: The temperature of the silicon wafer is controlled in the range of 425-435 DEG C, the mixed gas of silane, hydrogen and phosphine is introduced into the reaction chamber, the volume ratio of silane, hydrogen and phosphine in the mixed gas is controlled to be 10:34:3.0, the pressure in the reaction chamber is controlled to be 3050mtorr, the power of the square wave power source is adjusted to be 14500-15000W, the frequency of the power source is 40KHz, the duty cycle of the power source is 1:10, the glow discharge is excited in the reaction chamber to form a low temperature plasma, the running time of the square wave power source is in the range of 430-450s, and the second phosphorus-doped amorphous silicon layer is prepared on the second tunneling oxide layer.

[0057] S27: The temperature of the silicon wafer is controlled in the range of 425-435 DEG C, the mixed gas of silane and nitrogen dioxide is introduced into the reaction chamber, the volume ratio of silane and nitrogen dioxide in the mixed gas is controlled to be 1:4.3, the pressure in the reaction chamber is controlled to be 1750mtorr, the power of the square wave power source is adjusted to be 15000-15500W, the frequency of the power source is 40KHz, the duty cycle of the power source is 1:17.6, the glow discharge is excited in the reaction chamber to form a low temperature plasma, the running time of the square wave power source is in the range of 96-116s, and the mask layer is prepared on the second phosphorus-doped amorphous silicon layer.

[0058] In the present application, a TOPCon cell is also provided, which comprises a poly layer prepared by the PE-poly processing method as described above.

[0059] S28: The silicon wafer is blown by nitrogen, the reaction chamber is vacuumized, the nitrogen back pressure is filled into the reaction chamber again, the graphite boat is removed from the reaction chamber, and the silicon wafer is pressed out of the boat.

[0060] In the present application, a TOPCon cell is also provided, which comprises a poly layer prepared by the PE-poly processing method as described above.

[0061] The first embodiment and the second embodiment provided by the specific embodiment both use square wave power supply, and also use the method of sequentially preparing the first tunneling oxide layer, the first phosphorus-doped amorphous silicon layer, the second tunneling oxide layer, and the second phosphorus-doped amorphous silicon layer. The first embodiment is different from the second embodiment in the heating mode and specific parameters of square wave power supply process one and square wave power supply process two. The implementation of the two specific embodiments is tracked and compared, and three sets of comparative experiments are set up. Comparative group 4, comparative group 5, and comparative group 6 implement square wave power supply process one in the first embodiment, and experimental group 4, experimental group 5, and experimental group 6 implement square wave power supply process two in the second embodiment. The poly layer obtained after the implementation of the process is subjected to EL contamination detection, and the EL contamination ratio is shown in Table Three as follows:

[0062]

[0063] (Table Three, the table shows the EL contamination ratio data of the poly layer obtained by implementing square wave power supply process one and square wave power supply process two)

[0064] As shown in Table Three, in the first verification, the EL contamination ratio of the poly layer obtained by experimental group 4 implementing square wave power supply process two is reduced by 0.07% compared with the poly layer obtained by comparative group 4 implementing square wave power supply process one. In the second verification, the EL contamination ratio of the poly layer obtained by experimental group 5 implementing square wave power supply process two is reduced by 0.08% compared with the poly layer obtained by comparative group 5 implementing square wave power supply process one. In the third verification, the EL contamination ratio of the poly layer obtained by experimental group 6 implementing square wave power supply process two is reduced by 0.05% compared with the poly layer obtained by comparative group 6 implementing square wave power supply process one. Therefore, from the data, replacing the square wave power supply and matching the new poly process further suppresses the generation of poly dust.

[0065] The electrical performance parameters of the poly layer prepared in the above three sets of comparative experiments are tracked, the poly layer obtained after the implementation of the process is subjected to electrical performance detection, and the electrical performance test results are shown in Table Four as follows:

[0066]

[0067] (Table Four, the table shows the electrical performance detection data of the poly layer obtained by implementing square wave power supply process one and square wave power supply process two. In the table, Eta refers to the photoelectric conversion efficiency, Uoc refers to the open circuit voltage, Isc refers to the short circuit current, FF refers to the fill factor, Rs refers to the series resistance,

[0068] Rsh refers to the parallel resistance, and Irev2 refers to the leakage current)

[0069] As shown in Table 4, in the first verification, the poly layer obtained by the experimental group 4 using the square wave power supply process two has an electrical performance efficiency 0.0120% higher than that of the poly layer obtained by the comparative group 4 using the square wave power supply process one, in the second verification, the poly layer obtained by the experimental group 5 using the square wave power supply process two has an electrical performance efficiency 0.034% higher than that of the poly layer obtained by the comparative group 5 using the square wave power supply process one, and in the third verification, the poly layer obtained by the experimental group 6 using the square wave power supply process two has an electrical performance efficiency 0.03% higher than that of the poly layer obtained by the comparative group 6 using the square wave power supply process one. It can be seen that replacing the square wave power supply and matching the new poly process can improve the electrical performance efficiency of the poly layer to a certain extent.

[0070] In conclusion, the PE-poly processing method provided in the specific embodiment can effectively inhibit the generation of poly dust, improve the performance and yield of the battery, and provide a strong guarantee for the efficient production of solar cells.

[0071] The above only describes the preferred embodiments of the present application, and does not limit the patent scope of the present application. Any equivalent structural transformation, direct / indirect application in other related technical fields, or direct / indirect application in other related technical fields within the inventive concept of the present application and the content of the specification and drawings are included in the patent protection scope of the present application.

Claims

1. A PE-poly processing method, characterized in that, The processing method involves: sending the alkaline-polished silicon wafer into a reaction chamber, introducing a reaction gas into the reaction chamber, using a square wave power supply to induce glow discharge in the reaction chamber to construct a low-temperature plasma, and sequentially preparing a first tunneling oxide layer, a first phosphorus-doped amorphous silicon layer, a second tunneling oxide layer, and a second phosphorus-doped amorphous silicon layer on the surface of the silicon wafer, wherein the phosphorus content of the second phosphorus-doped amorphous silicon layer is greater than the phosphorus content of the first phosphorus-doped amorphous silicon layer.

2. The PE-poly processing method as described in claim 1, characterized in that, The processing method includes: S1: The silicon wafer after alkaline polishing is sent into the reaction chamber; S2: Heat the reaction chamber to raise the temperature of the silicon wafer to a preset temperature; S3: Nitrous oxide gas is introduced into the reaction chamber, and a square wave power supply is used to generate a glow discharge in the reaction chamber to prepare the first tunneling oxide layer on the silicon wafer surface. S4: A mixed gas consisting of silane, hydrogen and phosphine is introduced into the reaction chamber, and a square wave power supply is used to generate glow discharge in the reaction chamber to prepare the first phosphorus-doped amorphous silicon layer on the first tunneling oxide layer. S5: Nitrous oxide gas is introduced into the reaction chamber, and a square wave power supply is used to generate glow discharge in the reaction chamber to prepare the second tunneling oxide layer on the first phosphorus-doped amorphous silicon layer. S6: A mixed gas consisting of silane, hydrogen and phosphine is introduced into the reaction chamber, and a square wave power supply is used to generate glow discharge in the reaction chamber to prepare the second phosphorus-doped amorphous silicon layer on the second tunneling oxide layer. S7: Using a square wave power supply to generate glow discharge in the reaction chamber, the mask layer is prepared on the second phosphorus-doped amorphous silicon layer; S8: Purge the silicon wafer, evacuate the reaction chamber, and send the prepared silicon wafer out of the reaction chamber.

3. The PE-poly processing method as described in claim 2, characterized in that, S2 specifically involves: a constant-temperature heater and an auxiliary heater being installed within the reaction chamber. The constant-temperature heater is used to heat the silicon wafer, and it operates continuously to raise the temperature of the silicon wafer and maintain it within the range of 425°C-435°C. The auxiliary heater is used to heat the environment within the reaction chamber and the carrier carrying the silicon wafer. When the carrier carrying the silicon wafer enters the reaction chamber, the auxiliary heater starts operating to raise the temperature of the carrier. When the temperature of the carrier carrying the silicon wafer rises to the range of 460°C-480°C, or when the carrier carrying the silicon wafer leaves the reaction chamber, the auxiliary heater is turned off.

4. The PE-poly processing method as described in claim 2, characterized in that, S2 specifically refers to: at least one constant temperature heater and at least one auxiliary heater being provided in the reaction chamber; the constant temperature heater maintains a constant temperature of 425℃-435℃ for 450s at the current silicon wafer location, and then maintains a constant temperature of 425℃-435℃ for 300s; the auxiliary heater maintains an auxiliary temperature of 430℃ for 400s at the current silicon wafer location and its surrounding environment, and then maintains an auxiliary temperature of 420℃ for 300s.

5. The PE-poly processing method as described in claim 2, characterized in that, S3 specifically involves: introducing nitrous oxide gas into the reaction chamber, controlling the pressure inside the reaction chamber to be 1800 mtorr, setting the square wave power supply to 14700-15000W, the power supply frequency to 40KHz, and the power supply duty cycle to 1:80, exciting glow discharge in the reaction chamber, constructing low-temperature plasma, setting the running time of the square wave power supply to 69-92s, and preparing the first tunneling oxide layer with a thickness of 1-1.5nm on the surface of the silicon wafer.

6. The PE-poly processing method as described in claim 2, characterized in that, S4 specifically involves: introducing a mixed gas of silane, hydrogen, and phosphine into the reaction chamber, controlling the volume ratio of silane, hydrogen, and phosphine in the mixed gas to be within the range of 10:32:1.1 to 10:38:1.1, controlling the pressure of the reaction chamber to be 2800-3050 mtorr, adjusting the power of the square wave power supply to be 14500W-15000W, the power frequency to be 40KHz, and the power duty cycle to be within the range of 1:10 to 1:12, exciting glow discharge in the reaction chamber, constructing low-temperature plasma, and the running time of the square wave power supply to be 85-110s, thereby preparing the first phosphorus-doped amorphous silicon layer on the first tunneling oxide layer.

7. The PE-poly processing method as described in claim 2, characterized in that, S5 specifically involves: introducing nitrous oxide gas into the reaction chamber, controlling the pressure of the reaction chamber to be 1800-2200 mtorr, adjusting the power of the square wave power supply to be 14000-15000 W, the power frequency to be 40 kHz, and the power duty cycle to be 1:30, thereby exciting a glow discharge and constructing a low-temperature plasma in the reaction chamber, with the square wave power supply running for 35-45 s, and preparing a second tunneling oxide layer with a thickness of 1-1.5 nm on the first tunneling oxide layer.

8. The PE-poly processing method as described in claim 2, characterized in that, S6 specifically involves: introducing a mixed gas of silane, hydrogen, and phosphine into the reaction chamber, controlling the volume ratio of silane, hydrogen, and phosphine in the mixed gas to be within the range of 10:32:3.0 to 10:34:3.0, controlling the pressure of the reaction chamber to be within 3000-3050 mtorr, adjusting the power of the square wave power supply to be within 14500W-15000W, the power frequency to be 40KHz, and the power duty cycle to be within the range of 1:10 to 1:12, exciting glow discharge and constructing low-temperature plasma in the reaction chamber, with the running time of the square wave power supply within the range of 415-455s, and preparing the second phosphorus-doped amorphous silicon layer on the second tunneling oxide layer.

9. The PE-poly processing method as described in claim 2, characterized in that, S7 specifically involves: introducing a mixed gas of silane and nitrogen dioxide into the reaction chamber, controlling the volume ratio of silane to nitrogen dioxide in the mixed gas to be 1:4.3, controlling the pressure in the reaction chamber to be 1750 mtorr, adjusting the power of the square wave power supply to be 15000W-15500W, the power frequency to be 40KHz, and the power duty cycle to be in the range of 1:17.6 to 1:20, exciting glow discharge in the reaction chamber, constructing low-temperature plasma, and the running time of the square wave power supply to be in the range of 60-116s, thereby preparing the mask layer on the second phosphorus-doped amorphous silicon layer.

10. A TOPCon battery, characterized in that, The TOPCon battery includes a poly layer, which is prepared by the PE-poly processing method as described in any one of claims 1-9.

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