Phosphorus diffusion method, preparation method and application of TOPCon battery

Abstract

The invention discloses a phosphorus diffusion method, a preparation method and application of a TOPCon battery. The phosphorus diffusion method comprises the following steps: carrying out heating, first-time source-passing deposition, second-time source-passing deposition, aerobic propulsion treatment, anaerobic propulsion treatment, third-time source-passing deposition and cooling annealing on a silicon wafer with a tunneling oxide layer and an amorphous silicon layer formed on the back surface; the temperatures of the first time of source deposition, the second time of source deposition and the third time of source deposition are increased in sequence; the temperature of the aerobic propulsion treatment is higher than that of the second time of source introduction deposition; the temperature of the anaerobic propulsion treatment is higher than the temperature of the second time of source introduction deposition. According to the TOPCon battery prepared by the method, the integrity of the tunneling oxide layer can be ensured, chemical passivation of the surface of the silicon substrate is realized, and meanwhile, the TOPCon battery can be combined with doped polycrystalline silicon to realize selective collection of carriers and enhance the field passivation effect.

Description

Technical Field

[0001] The invention relates to a phosphorus diffusion method and a preparation method of a TOPCon battery and applications thereof. Background Art

[0002] Energy is the material basis for human survival and development. As a new type of energy, solar energy has the characteristics of being inexhaustible and inexhaustible. Therefore, it has always attracted widespread attention and photovoltaic technology has been continuously developing. As one of the current mainstream high-efficiency crystalline silicon solar cells, the main feature of the TOPCon cell is that an ultra-thin tunneling oxide layer and a doped polysilicon layer are prepared on the back of the cell, which together form a passivation contact structure. The tunneling oxide layer contacts the silicon substrate, neutralizes the dangling bonds on the silicon surface, and performs excellent chemical passivation; due to the difference in Fermi level between doped polysilicon and the silicon substrate, the band bending is caused on the surface of the silicon substrate, which can allow electrons to pass through and block holes, realizing the selective collection of carriers, thereby reducing the current loss caused by metal contact recombination and improving the battery conversion efficiency.

[0003] In the existing matching phosphorus diffusion process, the doping of phosphorus atoms directly affects the passivation effect: when the doping concentration is too high, more phosphorus atoms will enter the silicon substrate, the integrity of the tunneling oxide layer will be destroyed, and the selective collection of carriers cannot be achieved; when the doping concentration is too low, the concentration of phosphorus atoms reaching the tunneling oxide layer is insufficient, making it difficult to form the field passivation effect of the N / N+ structure, and at the same time affecting the contact with the metal electrode. Therefore, for the phosphorus diffusion process, finding the balance between the above two and improving the controllability of the process are the key to improving the conversion efficiency of TOPCon cells. Summary of the invention

[0004] In view of the shortcomings and deficiencies of the prior art, the present invention provides an improved phosphorus diffusion method for TOPCon cells. This method is used to dope the polysilicon in the TOPCon cell with phosphorus, which can not only ensure the integrity of the tunneling oxide layer and achieve chemical passivation of the silicon substrate surface, but also combine with the doped polysilicon to achieve selective collection of carriers and enhance the field passivation effect.

[0005] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0006] A phosphorus diffusion method for a TOPCon battery comprises the following steps: heating a silicon wafer having a tunneling oxide layer and an amorphous silicon layer formed on the back side, performing a first through-source deposition, a second through-source deposition, an aerobic driving treatment, an anaerobic driving treatment, a third through-source deposition and cooling annealing; the temperatures of the first through-source deposition, the second through-source deposition and the third through-source deposition are increased in sequence; the temperature of the aerobic driving treatment is higher than the temperature of the second through-source deposition; and the temperature of the anaerobic driving treatment is higher than the temperature of the second through-source deposition.

[0007] In the prior art, it is difficult to control the balanced phosphorus doping concentration in the phosphorus diffusion process. When the doping concentration is too high, more phosphorus atoms will enter the silicon substrate, the integrity of the tunneling oxide layer will be destroyed, and the selective collection of carriers cannot be achieved; when the doping concentration is too low, the concentration of phosphorus atoms reaching the tunneling oxide layer is insufficient, and it is difficult to form the field passivation effect of the N / N+ structure, and the contact with the metal electrode is affected. It is always difficult to simultaneously ensure the integrity of the tunneling oxide layer, achieve chemical passivation on the surface of the silicon substrate, and combine with the doped polysilicon to achieve selective collection of carriers, and enhance the field passivation effect. The inventors of the present application have discovered through research that, in the phosphorus diffusion process, by adopting three source passes with successively increasing temperatures, and sequentially performing aerobic boost treatment and anaerobic boost treatment after the second source pass, and controlling the temperature during the boost treatment to be higher than the temperature of the second source pass, it is possible to achieve stable control of the phosphorus doping concentration, thereby ensuring the integrity of the tunneling oxide layer and achieving chemical passivation of the silicon substrate surface, while also combining with the doped polysilicon to achieve selective collection of carriers and enhance the field passivation effect.

[0008] The present invention controls the doping of phosphorus atoms in a silicon wafer by three-way source passing, which is mainly the first low-temperature source passing - the second temperature-raising source passing - aerobic propulsion - oxygen-free propulsion - the third high-temperature source passing, and is controlled in steps. During the temperature-raising and source passing process, amorphous silicon is doped with phosphorus atoms while crystallizing, so that the distribution of phosphorus atoms in polysilicon is more uniform. At the same time, low-temperature diffusion ensures that a small amount of phosphorus atoms enter the silicon substrate, and a field passivation layer caused by concentration difference is formed on the surface of the silicon wafer, which is conducive to the separation and collection of carriers, thereby increasing the open circuit voltage; aerobic propulsion allows the surface phosphorus atoms to fully react, and superimposed oxygen-free propulsion allows the tunneling oxide layer to have a high concentration of phosphorus doping away from the substrate, thereby enhancing the field passivation effect; the third high-temperature source passing can appropriately increase the polysilicon doping concentration, while reducing the contact resistance between the back gate line and the silicon wafer.

[0009] In some embodiments, nitrogen and oxygen are introduced while the temperature is increased; the temperature of the silicon wafer after the temperature increase is 750-820°C.

[0010] Preferably, the total flow rate of nitrogen and oxygen is 1500-3000 sccm.

[0011] In some embodiments, the heating time is 1000-1500 seconds.

[0012] In some embodiments, in the first source deposition step, nitrogen, oxygen, and nitrogen containing phosphorus oxychloride are simultaneously introduced into the silicon wafer.

[0013] In some embodiments, the temperature of the first through-source deposition is 750-819°C.

[0014] In some embodiments, the first source deposition time is 200-500 s.

[0015] In some embodiments, the content of phosphorus oxychloride in the nitrogen gas containing phosphorus oxychloride is 0.0002-0.0003 g / mL.

[0016] In some embodiments, the flow rate of the introduced nitrogen gas is 700-1000 sccm.

[0017] In some embodiments, the flow rate of the introduced oxygen is 500-800 sccm.

[0018] In some embodiments, the flow rate of the nitrogen gas containing phosphorus oxychloride is 1500-1800 sccm.

[0019] In some embodiments, in the second source deposition step, nitrogen, oxygen, and nitrogen containing phosphorus oxychloride are simultaneously introduced into the silicon wafer.

[0020] In some embodiments, the temperature of the second through-source deposition is 820-849°C.

[0021] In some embodiments, the second source deposition time is 200-500 s.

[0022] In some embodiments, in the second through-source deposition step, the content of phosphorus oxychloride in the nitrogen gas containing phosphorus oxychloride is 0.0002-0.0003 g / mL.

[0023] In some embodiments, in the second source deposition step, the flow rate of the introduced nitrogen gas is 700-1000 sccm.

[0024] In some embodiments, in the second source deposition step, the flow rate of the introduced oxygen is 500-800 sccm.

[0025] In some embodiments, in the second source deposition step, the flow rate of the nitrogen gas containing phosphorus oxychloride is 1500-1800 sccm.

[0026] In some embodiments, during the aerobic boost treatment step, nitrogen and oxygen are simultaneously introduced into the silicon wafer.

[0027] Preferably, the flow rate of the nitrogen gas is 1000-1500 sccm, and the flow rate of the oxygen gas is 800-1000 sccm.

[0028] In some embodiments, the temperature of the aerobic propulsion treatment is 850-890°C.

[0029] In some embodiments, the aerobic propulsion treatment lasts for 200-500 seconds.

[0030] In some embodiments, during the oxygen-free drive-in treatment step, nitrogen gas is introduced into the silicon wafer.

[0031] Preferably, the flow rate of the nitrogen gas is 2000-2500 sccm.

[0032] In some embodiments, the temperature of the oxygen-free boost treatment is 850-890°C.

[0033] In some embodiments, the anaerobic propulsion treatment lasts for 500-1000 seconds.

[0034] In some embodiments, in the third source deposition step, nitrogen, oxygen, and nitrogen containing phosphorus oxychloride are simultaneously introduced into the silicon wafer.

[0035] In some embodiments, the temperature of the third through-source deposition is 850-890°C.

[0036] In some embodiments, the third source deposition takes 50-100 seconds.

[0037] In some embodiments, in the third through-source deposition step, the content of phosphorus oxychloride in the nitrogen gas containing phosphorus oxychloride is 0.0002-0.0003 g / mL.

[0038] In some embodiments, in the third source deposition step, the flow rate of the introduced nitrogen gas is 700-1000 sccm.

[0039] In some embodiments, in the third source deposition step, the flow rate of the introduced oxygen is 500-800 sccm.

[0040] In some embodiments, in the third source deposition step, the flow rate of the nitrogen gas containing phosphorus oxychloride is 1000-1600 sccm.

[0041] In some embodiments, during the temperature reduction annealing step, nitrogen gas is introduced into the silicon wafer.

[0042] Preferably, the flow rate of the nitrogen gas is 3500-5000 sccm.

[0043] In some embodiments, the temperature of the temperature-drop annealing is 700-800°C.

[0044] In some embodiments, the temperature reduction annealing time is 1000-1500s.

[0045] In some embodiments, the phosphorus diffusion method is performed in a phosphorus diffusion furnace.

[0046] In some embodiments, during the first through-source deposition, the second through-source deposition, the aerobic propulsion treatment, the anaerobic propulsion treatment, and the third through-source deposition steps, the pressure of the furnace tube is controlled at 120-150 mbar.

[0047] The present invention also provides a method for preparing a TOPCon battery, which includes the steps of cleaning and texturing an N-type silicon wafer, diffusing boron on the front side, removing BSG and polishing the back side, forming a tunneling oxide layer and an amorphous silicon layer on the back side, and diffusing phosphorus on the amorphous silicon layer. The phosphorus diffusion adopts the phosphorus diffusion method of the TOPCon battery described above in the present invention.

[0048] The conventional processes in the field can be used to clean and texture the N-type silicon wafer, diffuse boron on the front side, remove BSG and polish the back side, and form a tunnel oxide layer and an amorphous silicon layer on the back side. For example, the tunnel oxide layer can be formed on the back side by nitric acid oxidation, thermal oxidation or LPCVD.

[0049] The present invention also provides a TOPCon cell prepared by the above-mentioned TOPCon cell preparation method. The cell can ensure the integrity of the tunneling oxide layer and achieve chemical passivation on the surface of the silicon substrate, and can also be combined with doped polysilicon to achieve selective collection of carriers and enhance the field passivation effect.

[0050] Furthermore, the back side of the TOPCon cell includes, from top to bottom, an N-type silicon wafer, a back tunneling oxide layer, a back phosphorus-doped polysilicon layer, a back passivation layer and a back electrode.

[0051] Furthermore, the thickness of the back tunneling oxide layer is 1-2 nm.

[0052] Furthermore, the thickness of the back phosphorus-doped polysilicon layer is 100-150 nm.

[0053] Furthermore, the back passivation layer may include a back aluminum oxide layer and a back silicon nitride layer.

[0054] Furthermore, the front side of the TOPCon battery can adopt the conventional configuration of the battery, for example, a front side passivation layer, a front side electrode, etc. can be provided.

[0055] The present invention also provides the use of the above-mentioned TOPCon cell in a solar power generation device.

[0056] Compared with the prior art, the present invention has the following advantages:

[0057] The phosphorus diffusion process of the present invention can realize stable control of phosphorus doping concentration by adopting three source passes with successively increasing temperatures, and successively performing aerobic driving treatment and anaerobic driving treatment after the second source pass, and controlling the temperature during the driving treatment to be higher than the temperature of the second source pass, so as to ensure the integrity of the tunneling oxide layer and realize chemical passivation of the silicon substrate surface, and at the same time, can combine with the doped polysilicon to realize selective collection of carriers and enhance the field passivation effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] Figure 1 It is a schematic diagram of the structure of the TOPCon battery of the present invention;

[0059] Figure 2 It is the curve chart of ECV test results;

[0060] Figure 3 for Figure 2 A magnified view of the curve at the middle platform end;

[0061] Among them, 1-N-type silicon wafer, 2-back tunneling oxide layer, 3-back phosphorus-doped polysilicon layer, 4-back aluminum oxide layer, 5-back silicon nitride layer, 6-back electrode, 7-P + layer, 8-front aluminum oxide layer, 9-front silicon nitride layer, 10-front electrode. DETAILED DESCRIPTION

[0062] The present invention is further described below in conjunction with the examples. However, the present invention is not limited to the following examples. The implementation conditions used in the examples can be further adjusted according to the different requirements of specific use, and the implementation conditions not specified are conventional conditions in the industry. The technical features involved in each embodiment of the present invention can be combined with each other as long as they do not conflict with each other.

[0063] Embodiment 1

[0064] This embodiment provides a TOPCon battery, and the preparation method thereof is as follows:

[0065] Step 1: Select N-type silicon wafer as substrate material, clean it, and make texture;

[0066] Step 2: Diffusion of boron on the front side of the silicon wafer;

[0067] Step 3: Remove BSG and polish the back side of the silicon wafer;

[0068] Step 4: forming a tunnel oxide layer on the back of the silicon wafer by nitric acid oxidation method, the thickness of the tunnel oxide layer is 1nm; then forming an amorphous silicon layer on the tunnel oxide layer, the thickness of the amorphous silicon layer is 150nm;

[0069] Step 5: Phosphorus is diffused into the amorphous silicon layer on the back side of the silicon wafer by three-pass source diffusion, specifically including the following steps to obtain a back-doped polysilicon layer:

[0070] (1) Place the silicon wafer into a phosphorus diffusion furnace tube, keep the temperature at 780°C, and introduce N 2 and O 2 , with a total flow rate of 2000sccm and a time of 1400s, during which heating, evacuation, leak detection, voltage stabilization and temperature stabilization are completed;

[0071] (2) The first low temperature source was passed at 790 °C for 500 s and N 2 、N 2 (containing POCl 3 , POCl 3 The content is 0.0002g / mL) and O 2 , N 2 The flow rate is 900 sccm, N 2 (containing POCl 3 ) has a flow rate of 1800 sccm, O 2 The flow rate is 600sccm;

[0072] (3) The second heating source was set at 830°C for 200 s and N 2 、N 2 (containing POCl 3 , POCl 3 The content is 0.0002g / mL) and O 2 , N 2 The flow rate is 900 sccm, N 2 (containing POCl 3 ) has a flow rate of 1800 sccm, O 2 The flow rate is 600sccm;

[0073] (4) Aerobic propulsion, temperature 890°C, time 300 s, N 2 and O 2 , N 2 The flow rate is 1500sccm, O 2 The flow rate is 1000sccm;

[0074] (5) Anaerobic propulsion, temperature 890 °C, time 650 s, only N 2 , flow rate is 2500sccm;

[0075] (6) The third high temperature source was passed at 890 °C for 100 s. N 2 、N 2 (containing POCl 3 , POCl 3The content is 0.0002g / mL) and O 2 , N 2 The flow rate is 1000sccm, N 2 (containing POCl 3 ) has a flow rate of 1000 sccm, O 2 The flow rate is 500sccm;

[0076] (7) Annealing at 700 °C for 1500 s, with N 2 , flow rate is 5000sccm;

[0077] (8) The boat trip is over.

[0078] In the above phosphorus diffusion process, in steps (2), (3), (4), (5), and (6), the furnace tube pressure is controlled at 120 mbar.

[0079] Step 6: Remove PSG and RCA from the silicon wafer;

[0080] Step 7: forming a double-sided aluminum oxide layer and a front and back silicon nitride layer;

[0081] Step 8: Print to form the front and back electrodes.

[0082] The final structure of the TOPCon battery is as follows Figure 1 As shown, the back structure includes, from top to bottom, an N-type silicon wafer 1, a back tunneling oxide layer 2, a back phosphorus-doped polysilicon layer 3, a back aluminum oxide layer 4, a back silicon nitride layer 5, and a back electrode 6. The front structure includes, from bottom to top, a P + Layer 7, front aluminum oxide layer 8, front silicon nitride layer 9, front electrode 10.

[0083] Embodiment 2

[0084] This embodiment provides a TOPCon battery, and the preparation method thereof is as follows:

[0085] Step 1: Select N-type silicon wafer as substrate material, clean it, and make texture;

[0086] Step 2: Diffusion of boron on the front side of the silicon wafer;

[0087] Step 3: Remove BSG and polish the back side of the silicon wafer;

[0088] Step 4: forming a tunnel oxide layer on the back of the silicon wafer by thermal oxidation, the thickness of the tunnel oxide layer is 2nm; then forming an amorphous silicon layer on the tunnel oxide layer, the thickness of the amorphous silicon layer is 100nm;

[0089] Step 5: Phosphorus is diffused into the amorphous silicon layer on the back of the silicon wafer by three-pass source diffusion, which specifically includes the following steps:

[0090] (1) Place the silicon wafer into a phosphorus diffusion furnace tube, keep the temperature at 780°C, and introduce N 2 and O 2 , with a total flow rate of 2000sccm and a time of 1400s, during which heating, evacuation, leak detection, voltage stabilization and temperature stabilization are completed;

[0091] (2) The first low temperature source was passed at 800 °C for 500 s and N 2 、N 2 (containing POCl 3 , POCl 3 The content is 0.0003g / mL) and O 2 , N 2 The flow rate is 900 sccm, N 2 (containing POCl 3 ) has a flow rate of 1600 sccm, O 2 The flow rate is 600sccm;

[0092] (3) The second heating source was set at 840°C for 300 s and N 2 、N 2 (containing POCl 3 , POCl 3 The content is 0.0003g / mL) and O 2 , N 2 The flow rate is 900 sccm, N 2 (containing POCl 3 ) has a flow rate of 1600 sccm, O 2 The flow rate is 600sccm;

[0093] (4) Aerobic propulsion, temperature 890°C, time 300 s, N 2 and O 2 , N 2 The flow rate is 1500sccm, O 2 The flow rate is 1000sccm;

[0094] (5) Anaerobic propulsion, temperature 890 °C, time 650 s, only N 2 , flow rate is 2500sccm;

[0095] (6) The third high temperature source was passed at 890 °C for 100 s. N 2 、N 2 (containing POCl 3 , POCl 3 The content is 0.0003g / mL) and O 2 , N 2 The flow rate is 1000sccm, N2 (containing POCl 3 ) has a flow rate of 1000 sccm, O 2 The flow rate is 500sccm;

[0096] (7) Annealing at 700 °C for 1500 s, with N 2 , flow rate is 5000sccm;

[0097] (8) The boat trip is over.

[0098] In the above phosphorus diffusion process, in steps (2), (3), (4), (5), and (6), the furnace tube pressure is controlled at 120 mbar.

[0099] Step 6: Remove PSG and RCA from the silicon wafer;

[0100] Step 7: forming a double-sided aluminum oxide layer and a front and back silicon nitride layer;

[0101] Step 8: Print to form the front and back electrodes.

[0102] The structure of the TOPCon battery finally obtained is the same as that of Example 1.

[0103] Embodiment 3

[0104] This embodiment provides a TOPCon battery, and the preparation method thereof is as follows:

[0105] Step 1: Select N-type silicon wafer as substrate material, clean it, and make texture;

[0106] Step 2: Diffusion of boron on the front side of the silicon wafer;

[0107] Step 3: Remove BSG and polish the back side of the silicon wafer;

[0108] Step 4: forming a tunnel oxide layer on the back of the silicon wafer by LPCVD method, the thickness of the tunnel oxide layer is 2nm; then forming an amorphous silicon layer on the tunnel oxide layer, the thickness of the amorphous silicon layer is 125nm;

[0109] Step 5: Phosphorus is diffused into the amorphous silicon layer on the back of the silicon wafer by three-pass source diffusion, which specifically includes the following steps:

[0110] (1) Place the silicon wafer into a phosphorus diffusion furnace tube, keep the temperature at 780°C, and introduce N 2 and O 2 , with a total flow rate of 2000sccm and a time of 1400s, during which heating, evacuation, leak detection, voltage stabilization and temperature stabilization are completed;

[0111] (2) The first low temperature source was passed at 790 °C for 500 s and N 2、N 2 (containing POCl 3 , POCl 3 The content is 0.0002g / mL) and O 2 , N 2 The flow rate is 900 sccm, N 2 (containing POCl 3 ) has a flow rate of 1800 sccm, O 2 The flow rate is 600sccm;

[0112] (3) The second heating source was set at 840°C for 200 s and N 2 、N 2 (containing POCl 3 , POCl 3 The content is 0.0002g / mL) and O 2 , N 2 The flow rate is 900 sccm, N 2 (containing POCl 3 ) has a flow rate of 1800 sccm, O 2 The flow rate is 600sccm;

[0113] (4) Aerobic propulsion, temperature 890°C, time 300 s, N 2 and O 2 , N 2 The flow rate is 1500sccm, O 2 The flow rate is 1000sccm;

[0114] (5) Anaerobic propulsion, temperature 890 °C, time 650 s, only N 2 , flow rate is 2500sccm;

[0115] (6) The third high temperature source was passed at 890°C for 80 seconds. 2 、N 2 (containing POCl 3 , POCl 3 The content is 0.0002g / mL) and O 2 , N 2 The flow rate is 1000sccm, N 2 (containing POCl 3 ) has a flow rate of 1250 sccm, O 2 The flow rate is 600sccm;

[0116] (7) Annealing at 700 °C for 1500 s, with N 2 , flow rate is 5000sccm;

[0117] (8) The boat trip is over.

[0118] In the above phosphorus diffusion process, in steps (2), (3), (4), (5), and (6), the furnace tube pressure is controlled at 120 mbar.

[0119] Step 6: Remove PSG and RCA from the silicon wafer;

[0120] Step 7: forming a double-sided aluminum oxide layer and a front and back silicon nitride layer;

[0121] Step 8: Print to form the front and back electrodes.

[0122] The structure of the TOPCon battery finally obtained is the same as that of Example 1.

[0123] Comparative Example 1

[0124] This comparative example provides a TOPCon battery, and its preparation method is basically the same as that of Example 1, except that: during the phosphorus diffusion in step 5, step (6) is not performed, that is, the third high-temperature source is not performed.

[0125] Comparative Example 2

[0126] This comparative example provides a TOPCon battery, and its preparation method is basically the same as that of Example 1, except that: during the phosphorus diffusion in step 5, the temperature of the aerobic advancement in step (4) and the anaerobic advancement in step (5) are changed, and both temperatures are set to 820° C. That is, the advancement is carried out by cooling.

[0127] Comparative Example 3

[0128] This comparative example provides a TOPCon battery, and its preparation method is basically the same as that of Example 1, except that: in step 5, the order of the steps during phosphorus diffusion is adjusted to heating, first low-temperature source, aerobic advancement, anaerobic advancement, second heating source, third high-temperature source, cooling annealing, and the temperature of aerobic advancement and anaerobic advancement is set to 820°C. Step 5 is as follows:

[0129] (1) Place the silicon wafer into a phosphorus diffusion furnace tube, keep the temperature at 780°C, and introduce N 2 and O 2 , with a total flow rate of 2000sccm and a time of 1400s, during which heating, evacuation, leak detection, voltage stabilization and temperature stabilization are completed;

[0130] (2) The first low temperature source was passed at 790 °C for 500 s and N 2 、N 2 (containing POCl 3 , POCl 3 The content is 0.0002g / mL) and O 2 , N 2 The flow rate is 900 sccm, N2 (containing POCl 3 ) has a flow rate of 1800 sccm, O 2 The flow rate is 600sccm;

[0131] (3) Aerobic propulsion, temperature 820°C, time 300 s, N 2 and O 2 , N 2 The flow rate is 1500sccm, O 2 The flow rate is 1000sccm;

[0132] (4) Anaerobic propulsion, temperature 820 °C, time 650 s, only N 2 , flow rate is 2500sccm;

[0133] (5) The second heating was carried out at 830 °C for 200 s and N 2 、N 2 (containing POCl 3 , POCl 3 The content is 0.0002g / mL) and O 2 , N 2 The flow rate is 900 sccm, N 2 (containing POCl 3 ) has a flow rate of 1800 sccm, O 2 The flow rate is 600sccm;

[0134] (6) The third high temperature source was passed at 890 °C for 100 s. N 2 、N 2 (containing POCl 3 , POCl 3 The content is 0.0002g / mL) and O 2 , N 2 The flow rate is 1000sccm, N 2 (containing POCl 3 ) has a flow rate of 1000 sccm, O 2 The flow rate is 500sccm;

[0135] (7) Annealing at 700 °C for 1500 s, with N 2 , flow rate is 5000sccm;

[0136] (8) The boat trip is over.

[0137] The doping of phosphorus atoms in silicon wafers was observed by performing ECV (electrochemical capacitance-voltage method) tests on the TOPCon batteries in various embodiments and comparative examples. The specific operation steps are as follows: (1) Prepare a 10% volume fraction of ammonium bifluoride solution as a corrosive solution; (2) Turn on the test instrument and software; (3) Clean the rubber ring with pure water and blow it dry with an air gun to prevent it from contacting and contaminating the silicon wafer; (4) Place the sample, fix it with a probe, plug in the electrode, close the sample stage, and tighten the fixing button; (5) Select the sample test type as "N-type phosphorus doping", parameter settings: select Ring area, polished surface, and then set the test depth and save path as needed; (6) Start the test. The results are as follows Figure 2-3 As shown, it can be seen that the doping concentration of phosphorus atoms in the polysilicon layer in the battery of the embodiment is improved compared with that in the comparative example.

[0138] The TOPCon battery in each embodiment and comparative example was tested for minority carrier lifetime by quasi-steady-state photoconductivity method (test instrument Sinton WCT-120), with specific operation steps: (1) Turn on the computer and the temperature control switch of the test bench, and preheat for 30 minutes; (2) Open the test software, load the test recipe, set the sample type to n-type, and input parameters such as silicon wafer thickness and resistivity; (3) Zero the table; (4) Place the sample for testing. For accuracy, test 5 points (center and four corners) on each silicon wafer, and take the average value of the results. The results are shown in Table 1 below, where J0 / 2 refers to saturation current density, iVoc refers to implicit open circuit voltage, and iFF refers to implicit fill factor.

[0139] Table 1 Performance of each embodiment and comparative example

[0140] Minority carrier lifetime (μs) <![CDATA[J0 / 2(A / cm 2 )]]> iVoc(V) iFF(%) Embodiment 1 2529 5.9 0.728 85.801 Embodiment 2 2726 6.6 0.728 86.200 Embodiment 3 2337 7.2 0.725 85.956 Comparative Example 1 2024 8.8 0.722 85.935 Comparative Example 2 1523 9.8 0.717 85.302 Comparative Example 3 1700 10.8 0.718 85.759

[0141] It can be seen that the minority carrier lifetime of the TOPCon battery of the embodiment of the present invention is significantly longer than that of the comparative example, and iVoc and iFF are also improved to varying degrees, that is, the passivation effect is significantly improved. It can be seen that the specific phosphorus diffusion method of the present invention can not only ensure the integrity of the tunneling oxide layer and realize the chemical passivation of the silicon substrate surface, but also combine with the doped polysilicon to realize the selective collection of carriers and enhance the field passivation effect.

[0142] The above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with the technology to understand the content of the present invention and implement it accordingly, and they cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the protection scope of the present invention.

[0143] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

Claims

1. A phosphorus diffusion method for a TOPCon battery, characterized in that: The phosphorus diffusion method comprises the following steps: heating a silicon wafer having a tunneling oxide layer and an amorphous silicon layer formed on the back side, performing a first through-source deposition, a second through-source deposition, an aerobic drive treatment, an anaerobic drive treatment, a third through-source deposition and cooling annealing; the temperatures of the first through-source deposition, the second through-source deposition and the third through-source deposition are increased in sequence; the temperature of the aerobic drive treatment is higher than the temperature of the second through-source deposition; the temperature of the anaerobic drive treatment is higher than the temperature of the second through-source deposition.

2. The phosphorus diffusion method of TOPCon battery according to claim 1, characterized in that: In the first source deposition step, nitrogen, oxygen and nitrogen containing phosphorus oxychloride are simultaneously introduced into the silicon wafer; and / or, the temperature of the first source deposition is 750-819° C.; and / or, the time of the first source deposition is 200-500 s.

3. The phosphorus diffusion method of TOPCon battery according to claim 1, characterized in that: In the second source deposition step, nitrogen, oxygen and nitrogen containing phosphorus oxychloride are simultaneously introduced into the silicon wafer; and / or, the temperature of the second source deposition is 820-849° C.; and / or, the time of the first source deposition is 200-500 s.

4. The phosphorus diffusion method of TOPCon battery according to claim 1, characterized in that: In the aerobic driving treatment step, nitrogen and oxygen are introduced into the silicon wafer at the same time; preferably, the flow rate of the nitrogen is 1000-1500sccm, and the flow rate of the oxygen is 800-1000sccm; and / or, the temperature of the aerobic driving treatment is 850-890°C; and / or, the time of the aerobic driving treatment is 200-500s.

5. The phosphorus diffusion method of TOPCon battery according to claim 1, characterized in that: In the oxygen-free driving treatment step, nitrogen is introduced into the silicon wafer; preferably, the flow rate of the introduced nitrogen is 2000-2500sccm; and / or, the temperature of the oxygen-free driving treatment is 850-890°C; and / or, the time of the oxygen-free driving treatment is 500-1000s.

6. The phosphorus diffusion method of TOPCon battery according to claim 1, characterized in that: In the third source deposition step, nitrogen, oxygen and nitrogen containing phosphorus oxychloride are simultaneously introduced into the silicon wafer; and / or, the temperature of the third source deposition is 850-890° C.; and / or, the time of the third source deposition is 50-100 s.

7. The phosphorus diffusion method of TOPCon battery according to claim 6, characterized in that: In the third source deposition step, the content of phosphorus oxychloride in the nitrogen gas containing phosphorus oxychloride is 0.0002-0.0003 g / mL; and / or, in the third source deposition step, the flow rate of the nitrogen gas is 700-1000 sccm; and / or, in the third source deposition step, the flow rate of the oxygen gas is 500-800 sccm; and / or, in the third source deposition step, the flow rate of the nitrogen gas containing phosphorus oxychloride is 1000-1600 sccm.

8. A method for preparing a TOPCon cell, the method comprising the steps of cleaning and texturing an N-type silicon wafer, diffusing boron on the front side, removing BSG and polishing the back side, forming a tunneling oxide layer and an amorphous silicon layer on the back side, and diffusing phosphorus on the amorphous silicon layer; characterized in that: The phosphorus diffusion adopts the phosphorus diffusion method of the TOPCon cell according to any one of claims 1 to 7.

9. A TOPCon battery prepared by the method for preparing a TOPCon battery according to claim 8.

10. Use of the TOPCon cell according to claim 9 in a solar power generation device.

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