Method for removing edge BSG layer of boron-doped silicon wafer, boron-doped silicon wafer and Topcon cell

Abstract

The present invention provides a method for removing the edge BSG layer of a boron-doped silicon wafer, a boron-doped silicon wafer, and a Topcon cell. The removal method specifically includes the following steps: cutting the BSG coating around the edge of the boron-doped silicon wafer by laser to obtain a boron-doped silicon wafer with the edge BSG layer removed. The removal method of the present invention not only reduces the number of BSG removal cleaning cycles, reduces the chemical consumption, and reduces the risk of over-etching on the front side; but also eliminates the risk of BSG residue at the edge, reduces the leakage ratio of the finished product, and reduces the manufacturing cost; in particular, the laser scribing beam has a high energy density, and the scribing process is non-contact, without obvious collision contact with the silicon wafer itself, and the silicon wafer is not easily damaged or broken.

Description

Technical Field

[0001] The present invention relates to the technical field of TOPCon batteries, and in particular to a method for removing an edge BSG layer of a boron-doped silicon wafer, a boron-doped silicon wafer, and a Topcon battery. Background Art

[0002] During the process of manufacturing silicon ingots at the raw material end, the oxygen content of the silicon wafers at the head and tail of the silicon ingot is often much higher than that in the middle part. For silicon wafers with high oxygen content, oxygen precipitates will be formed after high-temperature processes (above 1000 °C) at the battery manufacturing end, and the EL shows concentric circle defects. Therefore, the PECVD deposition BSG boron doping method is adopted to replace the traditional high-temperature boron diffusion doping process. However, in the N-type TOPcon battery structure, the PN junction is made by doping boron source on the front side of the battery; a high-efficiency solar cell requires a low surface concentration emitter. During the boron diffusion process, an inactive boron-rich layer is inevitably formed. At the same time, in order to protect the front side of the battery from being damaged in subsequent processes, a long oxidation time is required to form a BSG (boron silicate glass) layer. The BSG layer is relatively thick and difficult to process. In particular, the BSG layer on the side edge of the silicon wafer is difficult to remove, increasing the risk of a high proportion of defective finished batteries.

[0003] The existing PECVD deposition BSG boron doping technology uses silane, nitrous oxide, boron source, and hydrogen for reaction to deposit a boron-doped silicon oxide layer. Nitrous oxide contains N ions during the ionization process, and SiON is simultaneously generated during the growth of the silicon oxide layer.

[0004] Currently, during the preparation of N-type TOPcon batteries, for the removal of the BSG layer, chain roller pickling is used for removal, that is, the lower surface and edge of the diffused solar cell wafer are etched with an acid etching solution to remove the deposited BSG layer on the edge. However, in the existing chain BSG removal process, there is only HF liquid, and the removal effect on SiON is poor. The process needs to be repeated multiple times, resulting in an increase in chemical consumption. At the same time, it increases the risk of over-etching on the front side and a high proportion of defective finished batteries, thus leading to a very low efficiency of removing the BSG layer by pickling the silicon wafer, further affecting the production process of the product. In addition, when the BSG layer is relatively thick, due to the high requirement for the HF concentration in the chain roller pickling process, the silicon wafer is extremely easy to be damaged and broken, and the production of high-concentration HF requires high requirements for equipment and the environment, and a large amount of harmful gases will also be generated.

[0005] In view of this, the present invention is specifically proposed. Summary of the Invention

[0006] One of the objectives of the present invention is to provide a method for removing the edge BSG layer of a boron-doped silicon wafer. The removal method specifically includes the following steps: cutting the BSG wrap plating on the edge of the boron-doped silicon wafer by laser to obtain a boron-doped silicon wafer with the edge BSG layer removed. The present invention uses laser cutting to remove the side BSG on the edge of the silicon wafer instead of the traditional wet HF method to remove the edge BSG layer. There is no obvious collision contact with the silicon wafer itself, and the silicon wafer is not easily damaged or broken.

[0007] Another objective of the present invention is to provide a boron-doped silicon wafer without an edge BSG wrap plating, which is prepared by the method for removing the edge BSG layer of the boron-doped silicon wafer as described above.

[0008] A third objective of the present invention is to provide a TOPCon solar cell, which includes the boron-doped silicon wafer without an edge BSG wrap plating as described above.

[0009] In order to achieve the above objectives of the present invention, the following technical solutions are specifically adopted:

[0010] In the first aspect, the present invention provides a method for removing the edge BSG layer of a boron-doped silicon wafer. The removal method specifically includes the following steps:

[0011] Cut the BSG wrap plating on the edge of the boron-doped silicon wafer by laser to obtain a boron-doped silicon wafer with the edge BSG layer removed.

[0012] In the present invention, laser cutting is used to remove the edge BSG layer of the boron-doped silicon wafer. This is because laser cutting uses a high-energy laser beam to irradiate the BSG wrap plating on the edge of the boron-doped silicon wafer, causing the irradiated area to melt and vaporize locally, and then laser cutting is carried out under the drive of a numerical control workbench to achieve the purpose of scribing. The energy density of the laser beam is high, the cutting effect is good, and its processing is non-contact, without mechanical impact force on the boron-doped silicon wafer itself, making the boron-doped silicon wafer not easily damaged or broken. In addition, the present invention uses laser cutting to remove the side BSG on the edge of the silicon wafer instead of the traditional wet HF method to remove the edge BSG layer. First, it reduces the number of BSG removal cleaning cycles, reduces the consumption of chemicals, and reduces the risk of over-etching on the front side; second, it reduces the risk of BSG residue on the edge, reduces the leakage ratio of the finished product, and reduces the manufacturing cost.

[0013] Preferably, the cutting length of the edge of the boron-doped silicon wafer is 0.5 - 5 mm, for example, it can be 0.5 mm, 1 mm, 1.5 mm, 2 mm, 2.5 mm, 3 mm, 3.5 mm, 4 mm, 4.5 mm, 5 mm, etc.

[0014] Preferably, the thickness of the cut edge of the boron-doped silicon wafer is 30 to 200 μm, and can be, for example, 30 μm, 40 μm, 60 μm, 80 μm, 100 μm, 120 μm, 140 μm, 160 μm, 180 μm, 200 μm, etc.

[0015] Preferably, the thickness of the BSG around-coating on the edge is 0 to 200 nm, and can be, for example, 0 nm, 10 nm, 20 nm, 40 nm, 60 nm, 80 nm, 100 nm, 120 nm, 140 nm, 160 nm, 180 nm, 200 nm, etc.

[0016] Preferably, the moving speed of the laser is 200 to 1000 mm / s, and can be, for example, 200 mm / s, 300 mm / s, 400 mm / s, 500 mm / s, 600 mm / s, 700 mm / s, 800 mm / s, 900 mm / s, 1000 mm / s, etc.

[0017] Preferably, the power of the laser is 5 to 25 W, and can be, for example, 5 W, 6 W, 8 W, 10 W, 12 W, 14 W, 16 W, 18 W, 20 W, 22 W, 24 W, 25 W, etc.

[0018] Preferably, the number of laser cutting times is 5 to 20 times, and can be, for example, 5 times, 6 times, 8 times, 10 times, 12 times, 14 times, 16 times, 18 times, 20 times, etc.

[0019] In the present invention, by adopting the above specific cutting parameters of the moving speed, power and number of times of the laser, the cutting of the BSG around-coating on the edge can be completed more uniformly and consistently, the risk of over-etching on the front side can be better reduced, the leakage ratio of the finished product can be reduced, and the silicon wafer can be ensured not to be easily damaged or broken.

[0020] As an optional technical solution of the present invention, the boron-doped silicon wafer is prepared by the following steps:

[0021] (a) Texturing both sides of the silicon substrate to obtain a silicon substrate with a textured surface;

[0022] (b) Depositing a BSG layer on the surface of the silicon substrate with a textured surface by PECVD deposition process;

[0023] (c) Using high-temperature diffusion to push the boron source in the BSG layer into the substrate to form a doped region.

[0024] In the present invention, first, the silicon substrate is textured to obtain a substrate with a textured surface morphology; a BSG layer is deposited on the front side of the substrate by PECVD; the boron source in the BSG layer is pushed into the substrate by high-temperature diffusion to form a doped region, and then the edge of the silicon wafer is cut by the SE process of the laser machine to remove the edge BSG.

[0025] Preferably, in step (a), the texturing specifically includes the following steps: cleaning the front and back surfaces of the silicon substrate with an alkaline solution to form a textured surface on the front and back surfaces of the silicon substrate.

[0026] Preferably, the alkaline substance in the alkaline solution is selected from any one or a combination of at least two of sodium hydroxide, potassium hydroxide, tetramethylammonium hydroxide, or polyethyleneimine.

[0027] Preferably, the mass percentage content of the alkaline substance in the alkaline substance solution is 0.1-1%, for example, it can be 0.1%, 0.2%, 0.3%, 0.35%, 0.4%, 0.45%, 0.5%, 0.55%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, etc.

[0028] Preferably, the alkaline substance solution further includes an additive.

[0029] Preferably, the additive includes any one or a combination of at least two of a buffer, a stabilizer, a dispersant, or a surfactant, and is preferably a combination of a buffer, a stabilizer, a dispersant, and a surfactant.

[0030] Preferably, the buffer is selected from any one or a combination of at least two of sodium silicate, sodium tartrate, sodium pyrophosphate, sodium 1-hydroxyethylidene-1,1-diphosphonate, or sodium ethylene diamine tetra (methylene phosphonate).

[0031] Preferably, the stabilizer is selected from any one or a combination of at least two of poloxamer, PEG-40 hydrogenated castor oil, or 2-amino-2-methyl-1-propanol;

[0032] Preferably, the dispersant is selected from any one or a combination of at least two of sodium lignin sulfonate, carboxymethyl cellulose, sodium carboxymethyl cellulose, or hydroxyethyl cellulose;

[0033] Preferably, the surfactant is selected from any one or a combination of at least two of sodium dodecylbenzenesulfonate, sodium dodecyl sulfate, or sodium dodecyl phosphate.

[0034] Preferably, the mass percentage content of the additive in the alkaline solution is 0.01-1%, for example, it can be 0.01%, 0.02%, 0.04%, 0.06%, 0.08%, 0.1%, 0.2%, 0.3%, 0.35%, 0.4%, 0.45%, 0.5%, 0.55%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, etc.

[0035] Preferably, the addition amount of the buffer is 0.05-0.2%, for example, it can be 0.05%, 0.06%, 0.08%, 0.1%, 0.15%, 0.2%, etc.

[0036] Preferably, the addition amount of the stabilizer is 0.05-0.2%, for example, it can be 0.05%, 0.06%, 0.08%, 0.1%, 0.15%, 0.2%, etc.

[0037] Preferably, the addition amount of the dispersant is 0.01-0.06%, for example, it can be 0.01%, 0.02%, 0.04%, 0.06%, etc.

[0038] Preferably, the addition amount of the surfactant is 0.01-0.06%, for example, it can be 0.01%, 0.02%, 0.04%, 0.06%, etc.

[0039] Preferably, the temperature of the cleaning is 70-80 °C, for example, it can be 70 °C, 72 °C, 74 °C, 76 °C, 78 °C, 80 °C, etc.

[0040] Preferably, the time of the cleaning is 150-450 s, for example, it can be 150 s, 200 s, 250 s, 300 s, 350 s, 400 s, 450 s, etc.

[0041] Preferably, the silicon substrate is an N-type silicon wafer.

[0042] Preferably, the textured surface is a pyramid-shaped textured surface.

[0043] In the present invention, by using the above specific lye, temperature, time and other conditions for texturing, the pyramid-shaped textured surface can be made small in size and uniform in textured surface structure, and the pyramid structure is macroscopically uniform, the microscopic surface is smooth and has few defects, thereby reducing the reflectivity and improving the battery efficiency.

[0044] Preferably, in step (b), the PECVD deposition process specifically includes the following steps: adopting the PECVD deposition process, introducing N 2 O, SiH 4 , B 2 H 6 and H 2 , and depositing to form the BSG layer.

[0045] In the present invention, the PECVD deposition process is used to deposit a BSG layer with a specified thickness, and N 2 O, SiH 4 , B 2 H 6 and H 2The deposition method can ensure the cleanliness of the BSG layer and avoid the introduction of excess impurities that may affect the performance of the subsequent TOPCon cells.

[0046] Preferably, the thickness of the BSG layer is 60 - 200 nm, such as 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, 110 nm, 120 nm, 130 nm, 140 nm, 160 nm, 180 nm, 200 nm, etc.

[0047] Preferably, the deposition temperature of the BSG layer is 300 - 400 °C, such as 300 °C, 310 °C, 320 °C, 330 °C, 340 °C, 350 °C, 360 °C, 370 °C, 380 °C, 390 °C, 400 °C, etc.

[0048] Preferably, the deposition time of the BSG layer is 30 - 90 min, such as 30 min, 40 min, 50 min, 60 min, 70 min, 80 min, 90 min, etc.

[0049] Preferably, the 2 flow ratio of N 4 O to SiH

[0050] is (5 - 9):1, such as 5:1, 5.5:1, 6:1, 6.5:1, 7:1, 7.5:1, 8:1, 8.5:1, 9:1, etc. 2 flow ratio of B 6 H 4 to SiH

[0051] is (4 - 10):1, such as 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, etc. 2 Preferably, the flow rate of H

[0052] is 2000 - 8000 sccm, such as 2000 sccm, 2500 sccm, 3000 sccm, 3500 sccm, 4000 sccm, 4500 sccm, 5000 sccm, 5500 sccm, 6000 sccm, 6500 sccm, 7000 sccm, 7500 sccm, 8000 sccm, etc.

[0053] Preferably, in step (c), the sheet resistance of the doped region is 80 - 500 Ω, such as 80 Ω, 85 Ω, 90 Ω, 95 Ω, 100 Ω, 150 Ω, 200 Ω, 250 Ω, 300 Ω, 350 Ω, 400 Ω, 450 Ω, 500 Ω, etc.

[0053] Preferably, in step (c), the surface concentration of the doped region is 1×1015 cm -3 ~1 × 10 20 cm -3 , for example, it can be 1 × 10 15 cm -3 、1 × 10 16 cm -3 、1 × 10 17 cm -3 、1 × 10 18 cm -3 、1 × 10 19 cm -3 、1 × 10 20 cm -3 etc.

[0054] Preferably, in step (c), the high - temperature promotion is carried out by using a chain diffusion furnace and / or a tube diffusion furnace.

[0055] Preferably, when using a chain diffusion furnace for high - temperature promotion, the chain diffusion furnace is provided with a constant - temperature zone, and the temperature of the constant - temperature zone is controlled at 900 - 1100 °C. For example, it can be 900 °C, 950 °C, 1000 °C, 1050 °C, 1100 °C, etc. The silicon wafer is promoted at high temperature in the constant - temperature zone for 200 - 1000 s. For example, it can be 200 s, 300 s, 400 s, 500 s, 600 s, 700 s, 800 s, 900 s, 1000 s, etc.

[0056] Preferably, when using a tube diffusion furnace for high - temperature promotion, the temperature of the tube diffusion furnace is controlled at 800 - 1200 °C. For example, it can be 800 °C, 850 °C, 900 °C, 950 °C, 1000 °C, 1050 °C, 1100 °C, 1150 °C, 1200 °C, etc. The time for high - temperature oxidation promotion is 1000 - 3000 s. For example, it can be 1000 s, 1200 s, 1400 s, 1600 s, 1800 s, 2000 s, 2200 s, 2400 s, 2600 s, 2800 s, 3000 s, etc.

[0057] In a second aspect, the present invention provides a boron - doped silicon wafer without BSG - wrapped coating on the edge, and the boron - doped silicon wafer is prepared by the method for removing the BSG layer on the edge of the boron - doped silicon wafer as described in the first aspect.

[0058] In a third aspect, the present invention provides a TOPCon solar cell, and the TOPCon solar cell includes the boron - doped silicon wafer without BSG - wrapped coating on the edge as described in the second aspect.

[0059] Compared with the prior art, the present invention has the following beneficial effects:

[0060] (1) The method for removing the edge BSG layer of the present invention reduces the number of BSG cleaning cycles, reduces the consumption of chemicals, and reduces the risk of over-etching on the front side;

[0061] (2) The method for removing the edge BSG layer of the present invention effectively eliminates the risk of edge BSG residue, reduces the leakage ratio of finished products, and reduces the manufacturing cost;

[0062] (3) The method for removing the edge BSG layer of the present invention uses laser cutting. The energy density of the laser beam is high, and the scribing process is non-contact, without obvious collision contact with the silicon wafer itself, so the silicon wafer is not easily damaged. BRIEF DESCRIPTION OF THE DRAWINGS

[0063] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0064] Figure 1 It is a schematic flow chart of the method for removing the edge BSG layer of the boron-doped silicon wafer.

[0065] Figure 2 It is a front view of the laser cutting position of the boron-doped silicon wafer provided by the present invention.

[0066] Figure 3 It is a top view of the laser cutting position of the boron-doped silicon wafer provided by the present invention.

[0067] Among them, 1 is the silicon substrate, 21 is the front BSG layer, 22 is the edge BSG coating, and 3 is the laser cutting line. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0068] Unless otherwise defined herein, scientific and technical terms used in conjunction with the present invention shall have the meanings commonly understood by those of ordinary skill in the art. The meanings and scopes of the terms should be clear. However, in any case of potential ambiguity, the definitions provided herein shall prevail over any dictionary or extrinsic definition. In this application, unless otherwise stated, the use of "or" means "and / or". In addition, the use of the term "including" and other forms is non-restrictive.

[0069] It should be noted that specific details are set forth in the following description to facilitate a thorough understanding of the present invention. However, the present invention can be implemented in many other ways different from those described herein, and those skilled in the art can make similar generalizations without departing from the connotation of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed below.

[0070] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be construed as a limitation on the present invention. In addition, the terms "first", "second", "third" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance.

[0071] As Figure 1 shown, the present invention provides a method for removing the edge BSG layer of a boron-doped silicon wafer. The method may include the following steps: first, the silicon substrate is subjected to texturing processing to obtain a substrate with a textured surface; a BSG layer is deposited on the front surface of the substrate by PECVD; the boron source in the BSG layer is pushed into the substrate by high-temperature diffusion to form a doped region, and then the edge of the silicon wafer is cut by a laser machine SE process to remove the edge BSG.

[0072] As Figure 2 and Figure 3 shown, the edge of the silicon wafer is cut by a laser machine SE process to remove the edge BSG.

[0073] Next, the technical solutions of the present invention will be described clearly and completely in conjunction with the embodiments. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts shall fall within the protection scope of the present invention.

[0074] The present invention will be further described below through embodiments. Unless otherwise specified, the materials in the embodiments are prepared according to existing methods or directly purchased from the market.

[0075] Preparation Example 1

[0076] This preparation example provides a method for preparing a boron-doped silicon wafer. The method for preparing the boron-doped silicon wafer specifically includes the following steps:

[0077] S1. Texturing:

[0078] The front and back surfaces of the silicon substrate are cleaned with an alkaline solution to form a pyramid textured surface on the front and back surfaces of the silicon substrate, and a silicon substrate with a textured surface is obtained;

[0079] Among them, the silicon substrate is an N-type silicon wafer, the resistivity of the silicon substrate is 1 Ω·cm, and the thickness is 120 μm;

[0080] Among them, the alkaline substance solution includes: 0.3% sodium hydroxide, 0.1% sodium tartrate, 0.1% 2-amino-2-methyl-1-propanol, 0.03% sodium lignosulfonate, 0.02% sodium dodecylbenzenesulfonate, and the balance is water; the cleaning temperature is 75°C and the cleaning time is 300 s.

[0081] S2. Deposit the BSG layer:

[0082] Put the silicon substrate with a textured surface into a PECVD furnace to deposit BSG on the silicon substrate, forming a BSG layer with a thickness of 90 nm on the front side; the thickness of the BSG overcoat layer at the edge is 90 nm;

[0083] Among them, the deposition temperature is 320°C, the deposition time is 90 min, and the N 2 O / SiH 4 flow ratio is 5:1, and the B 2 H 6 / SiH 4 flow ratio is 7:1, and the H 2 flow rate is 6000 sccm.

[0084] S3. High-temperature drive

[0085] Use high-temperature drive to push the boron source in the BSG layer into the substrate to form a doped region;

[0086] Among them, the sheet resistance of the doped region is 300 Ω; the surface concentration of the doped region is 1×10 19 cm -3 ; use a chain diffusion furnace for high-temperature drive. The chain diffusion furnace is provided with a constant temperature zone, and the temperature of the constant temperature zone is controlled at 1000°C. The silicon wafer is driven at high temperature in the constant temperature zone for 600 s.

[0087] Example 1

[0088] This example provides a method for removing the BSG overcoat layer at the edge of a boron-doped silicon wafer. The removal method includes the following steps:

[0089] Cut the BSG overcoat layer at the edge of the boron-doped silicon wafer obtained in Preparation Example 1 by laser to obtain a boron-doped silicon wafer with the BSG layer at the edge removed;

[0090] Among them, the cutting length at the edge of the boron-doped silicon wafer is 1 mm; the cutting thickness at the edge is 120 μm;

[0091] Among them, the moving speed of the laser is 400 mm / s; the power of the laser is 10 W; the number of cutting times is 8 times.

[0092] Example 2

[0093] This embodiment provides a method for removing the edge BSG layer of a boron-doped silicon wafer. The removal method includes the following steps:

[0094] Cut the BSG coating layer on the edge of the boron-doped silicon wafer obtained in Preparation Example 1 by laser to obtain a boron-doped silicon wafer with the edge BSG layer removed;

[0095] Among them, the cutting length of the edge of the boron-doped silicon wafer is 2 mm; the cutting thickness of the edge is 120 μm;

[0096] Among them, the moving speed of the laser is 500 mm / s; the power of the laser is 12 W; the number of cutting times is 10 times.

[0097] Example 3

[0098] This embodiment provides a method for removing the edge BSG layer of a boron-doped silicon wafer. The removal method includes the following steps:

[0099] Cut the BSG coating layer on the edge of the boron-doped silicon wafer obtained in Preparation Example 1 by laser to obtain a boron-doped silicon wafer with the edge BSG layer removed;

[0100] Among them, the cutting length of the edge of the boron-doped silicon wafer is 3 mm; the cutting thickness of the edge is 120 μm;

[0101] Among them, the moving speed of the laser is 800 mm / s; the power of the laser is 15 W; the number of cutting times is 15 times.

[0102] Example 4

[0103] This embodiment provides a method for removing the edge BSG layer of a boron-doped silicon wafer. The removal method includes the following steps:

[0104] Cut the BSG coating layer on the edge of the boron-doped silicon wafer obtained in Preparation Example 1 by laser to obtain a boron-doped silicon wafer with the edge BSG layer removed;

[0105] Among them, the cutting length of the edge of the boron-doped silicon wafer is 2 mm; the cutting thickness of the edge is 120 μm;

[0106] Among them, the moving speed of the laser is 100 mm / s; the power of the laser is 30 W; the number of cutting times is 25 times.

[0107] Example 5

[0108] This embodiment provides a method for removing the edge BSG layer of a boron-doped silicon wafer. The removal method includes the following steps:

[0109] Cut the BSG coating layer on the edge of the boron-doped silicon wafer obtained in Preparation Example 1 by laser to obtain a boron-doped silicon wafer with the edge BSG layer removed;

[0110] Among them, the cutting length of the edge of the boron-doped silicon wafer is 2 mm; the cutting thickness of the edge is 120 μm;

[0111] Among them, the moving speed of the laser is 1200 mm / s; the power of the laser is 4 W; the number of cutting times is 4 times.

[0112] Comparative Example 1

[0113] This comparative example provides a method for removing the BSG layer on the edge of a boron-doped silicon wafer, and the removal method includes the following steps:

[0114] (1) Place the silicon wafer provided in Preparation Example 1 in an HF solution with a mass concentration of 15%, and perform the first pickling on the silicon wafer at a solution temperature of 25°C to remove particle contamination and metal ions on the silicon wafer, and control the cleaning time to be 300 s;

[0115] (2) Place the silicon wafer in an HF solution with a mass concentration of 10%, and perform the second pickling on the silicon wafer at room temperature to remove metal ion contamination on the silicon wafer, remove the surface oxide film of the silicon wafer and form a hydrophobic surface, and achieve surface hydrogen passivation, and control the third pickling time to be 200 s;

[0116] (3) Place the silicon wafer in an HF solution with a mass concentration of 5%, and perform the third pickling on the silicon wafer at room temperature to remove metal ion contamination on the silicon wafer, remove the surface oxide film of the silicon wafer and form a hydrophobic surface, and achieve surface hydrogen passivation, and control the third pickling time to be 100 s.

[0117] Performance Test

[0118] Test samples: Boron-doped silicon wafers with the BSG layer removed on the edge provided in Examples 1 to 5, and boron-doped silicon wafers with the BSG layer removed on the edge provided in Comparative Example 1;

[0119] The test results are shown in Table 1 below:

[0120] Table 1

[0121]

[0122]

[0123] As shown in Table 1, the removal method of the present invention not only reduces the number of BSG cleaning cycles, reduces the consumption of chemicals, and reduces the risk of over-etching on the front side; but also removes the risk of BSG residue on the edge, reduces the leakage ratio of the finished product, and reduces the manufacturing cost; in particular, the laser scribing beam has a high energy density, and the scribing process is non-contact, without obvious collision contact with the silicon wafer itself, and the silicon wafer is not easily damaged.

[0124] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for removing a BSG layer at the edge of a boron-doped silicon wafer, characterized in that: The removal method specifically comprises the following steps: The BSG coating around the edge of the boron-doped silicon wafer is cut by laser to obtain a boron-doped silicon wafer with the BSG layer removed from the edge; The moving speed of the laser is 200-1000 mm / s; the power of the laser is 5-25 W; the number of cutting times of the laser is 5-20 times; The boron-doped silicon wafer is prepared by the following steps: (a) Texturing the double sides of a silicon substrate to obtain a silicon substrate with a velvet surface; wherein the texturing specifically comprises the following steps: using an alkali solution to clean the front and back sides of the silicon substrate to form a velvet surface on the front and back sides of the silicon substrate; the alkali solution comprises: 0.1-1% alkaline substance, 0.05-0.2% buffer, 0.05-0.2% stabilizer, 0.01-0.06% dispersant and 0.01-0.06% surfactant; the alkaline substance is selected from sodium hydroxide, the buffer is selected from sodium tartrate, the stabilizer is selected from 2-amino-2-methyl-1-propanol, the dispersant is selected from sodium lignin sulfonate, and the surfactant is selected from sodium dodecylbenzene sulfonate; the cleaning temperature is 70-80°C, and the cleaning time is 150-450s; (b) using a PECVD deposition process to deposit a BSG layer on the surface of the silicon substrate having a velvet surface; the PECVD deposition process specifically comprises the following steps: using a PECVD deposition process to introduce N2O, SiH4, B2H6 and H2 into the silicon substrate to deposit and form the BSG layer; the flow ratio between N2O and SiH4 is (5-9):1; the flow ratio between B2H6 and SiH4 is (4-10):1; (c) High temperature driving is used to drive the boron source in the BSG layer into the substrate to form a doped region.

2. The method for removing the BSG layer at the edge of a boron-doped silicon wafer according to claim 1, characterized in that: The cutting length of the edge of the boron-doped silicon wafer is 0.5-5 mm.

3. The method for removing the BSG layer at the edge of a boron-doped silicon wafer according to claim 1, characterized in that: The thickness of the cut edge of the boron-doped silicon wafer is 30-200 μm.

4. The method for removing the BSG layer at the edge of a boron-doped silicon wafer according to claim 1, characterized in that: The thickness of the BSG coating around the edge is 10-9200 nm.

5. The method for removing the BSG layer at the edge of a boron-doped silicon wafer according to claim 1, characterized in that: The silicon substrate is an N-type silicon wafer.

6. The method for removing the BSG layer at the edge of a boron-doped silicon wafer according to claim 1, characterized in that: The thickness of the BSG layer is 60-200 nm.

7. The method for removing the BSG layer at the edge of a boron-doped silicon wafer according to claim 1, characterized in that: The deposition temperature of the BSG layer is 300-400° C.; the deposition time of the BSG layer is 30-90 min.

8. The method for removing the BSG layer at the edge of a boron-doped silicon wafer according to claim 1, characterized in that: The flow rate of H2 is 2000~8000 sccm.

9. The method for removing the BSG layer at the edge of a boron-doped silicon wafer according to claim 1, characterized in that: In step (c), the sheet resistance of the doped region is 80-500Ω.

10. The method for removing the BSG layer at the edge of a boron-doped silicon wafer according to claim 1, characterized in that: In step (c), the surface concentration of the doped region is 1×10 15 cm -3 ~1×10 20 cm -3 .

11. The method for removing the BSG layer at the edge of a boron-doped silicon wafer according to claim 1, characterized in that: In step (c), the high temperature advancement adopts a chain diffusion furnace and / or a tubular diffusion furnace.

12. The method for removing the BSG layer at the edge of a boron-doped silicon wafer according to claim 1, characterized in that: A chain diffusion furnace is used for high-temperature advancement. The chain diffusion furnace is provided with a constant temperature zone. The temperature of the constant temperature zone is controlled at 900~1100℃. The silicon wafer is advanced at high temperature in the constant temperature zone for 200~1000 s.

13. The method for removing the BSG layer at the edge of a boron-doped silicon wafer according to claim 1, characterized in that: A tubular diffusion furnace is used for high temperature advancement. The temperature of the tubular diffusion furnace is controlled at 800~1200℃, and the time of high temperature oxidation advancement is 1000~3000 s.

14. A boron-doped silicon wafer without BSG coating around the edge, characterized in that: The boron-doped silicon wafer is prepared by the method for removing the edge BSG layer of the boron-doped silicon wafer according to any one of claims 1 to 13.

15. A TOPCon solar cell, characterized in that: The TOPCon solar cell comprises a boron-doped silicon wafer without a BSG coating around the edge as claimed in claim 14 .

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