Method for processing silicon substrate, solar cell and manufacturing method thereof
By employing a wet etching process combined with alkaline and acidic solution treatment on the silicon substrate, the problem of difficult removal of silicon substrate residues has been solved, achieving efficient and low-cost silicon substrate treatment, thereby improving the quality and efficiency of solar cells.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- LONGI SOLAR TECHNOLOGY (TAIZHOU) CO LTD
- Filing Date
- 2021-07-12
- Publication Date
- 2026-07-07
AI Technical Summary
During the fabrication of solar cells, residues on the surface of the silicon substrate are difficult to remove, affecting substrate quality and working efficiency. Furthermore, existing processes are complex and costly.
The amorphous silicon layer is removed using a first wet removal process while keeping the silicon substrate moist. Then, the oxide layer and tunneling layer are removed using a second wet process. The etching process, which combines alkaline and acidic solutions, avoids the drying and adhesion of impurities and dirt, thus simplifying the process flow.
It improves the cleanliness and processing efficiency of silicon substrates, reduces production costs, simplifies process steps, protects functional structures, and enhances the quality and performance of solar cells.
Smart Images
Figure CN115621355B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of photovoltaic technology, and in particular to a method for processing a silicon substrate, a solar cell, and a method for manufacturing the same. Background Technology
[0002] In the fabrication of solar cells, there are often multiple removal processes. For example, the oxide layer produced during the fabrication of the pn junction and the coating layer produced during the fabrication of the passivation contact structure both need to be removed through removal processes.
[0003] In the process of removing the plating layer first and then the oxide layer, the earlier removal process can easily leave residues on the silicon substrate. These residues on the silicon substrate are difficult to remove and can affect the quality of the silicon substrate and work efficiency. Summary of the Invention
[0004] The purpose of this invention is to provide a method for processing a silicon substrate, a solar cell, and a method for manufacturing the same, so as to remove residues carried on the surface of the silicon substrate.
[0005] In a first aspect, the present invention provides a method for processing a silicon substrate. The method for processing the silicon substrate includes the following steps:
[0006] A silicon substrate is provided, the silicon substrate having a first side and a second side opposite to each other; the first side has a first oxide layer, a tunneling layer formed by a coating process, and an amorphous silicon layer stacked together;
[0007] The amorphous silicon layer around the silicon substrate is removed using a first wet removal process;
[0008] The silicon substrate around which the amorphous silicon layer is removed is kept constantly wet, and the first oxide layer and the tunneling layer are removed using a second wet removal process.
[0009] When employing the above technical solution, during the processes of removing the amorphous silicon layer around the silicon substrate using the first wet removal process, removing the first oxide layer and the tunneling layer using the second wet removal process, and between the first and second wet removal processes, the silicon substrate for which the amorphous silicon layer is being removed is kept constantly moist. At this time, the surface of the silicon substrate has a significant amount of moisture. After the amorphous silicon layer is removed using the first wet removal process, when the silicon substrate carries impurities and contaminants, these impurities and contaminants mix with the moisture on the silicon substrate surface and remain in a free state. This prevents the impurities and contaminants from firmly adhering to the silicon substrate surface after drying. In subsequent second wet removal processes or other cleaning processes, the free and moist impurities and contaminants can be easily washed away and cleaned. Therefore, keeping the silicon substrate for which the amorphous silicon layer is being removed constantly moist during the silicon substrate processing facilitates the cleaning of impurities and contaminants on the silicon substrate surface, thereby improving the cleanliness of the silicon substrate, increasing the processing efficiency, and enhancing the quality of the silicon substrate.
[0010] Compared to existing technologies that involve HF cleaning, water washing, and drying between the first and second wet removal processes, the silicon substrate treatment method of the present invention omits these steps, resulting in a simpler process and lower production costs. Furthermore, it avoids the situation where dried impurities and dirt adhere firmly to the silicon substrate during the drying process, making it easier to clean impurities and dirt from the silicon substrate surface.
[0011] In some implementations, the equipment for the first wet removal process is a chain-type single-sided removal device, which is selected from roller-type single-sided etching equipment and conveyor-type single-sided etching equipment. In this case, the chain-type single-sided removal device can perform single-sided processing on the silicon substrate, removing only the amorphous silicon layer around the first side of the silicon substrate, without processing the second side of the silicon substrate, thereby better protecting the semiconductor structure on the second side of the silicon substrate.
[0012] In some implementations, the equipment for the first wet removal process described above is an immersion etching tank.
[0013] In some implementations, the etchant in the first wet removal process is an alkaline solution, which includes at least one of KOH, NaOH, or an organic alkaline reagent. In this case, the alkaline solution can chemically react with the amorphous silicon material, thereby removing the layer surrounding the amorphous silicon. Simultaneously, the alkaline solution does not react with oxide materials, or reacts very slowly with them, thus avoiding damage to the pn junctions and functional structures on the first and second surfaces of the silicon substrate by the first wet removal process. Compared to acidic etchants such as nitric acid, alkaline solutions are not only cheaper but also have lower wastewater treatment costs, reducing production costs.
[0014] In some implementations, after removing the amorphous silicon layer around the silicon substrate and before removing the first oxide layer and the tunneling layer, the silicon substrate treatment method further includes washing the silicon substrate with water. In this case, water washing can remove residual alkaline etchant from the silicon substrate surface, thereby preventing residual alkaline solution from interfering with the subsequent second wet removal process and ensuring the quality of the second wet removal process.
[0015] In some implementations, after washing the silicon substrate and before removing the first oxide layer and the tunneling layer, the silicon substrate treatment method further includes: keeping the silicon substrate from which the amorphous silicon layer has been removed constantly wet, cleaning the silicon substrate with a first acidic solution, and then washing the silicon substrate with water; wherein the first acidic solution contains HCl, or the first acidic solution contains HCl and HF; and the equipment for cleaning the silicon substrate is an immersion etching tank.
[0016] When the first acidic solution contains HCl, the HCl can neutralize the alkaline solution residue on the silicon substrate surface, thus facilitating the cleaning of the residue. When the first acidic solution contains both HCl and HF, the chemical reaction between HF and silicon oxide can etch the tunneling layer and the first oxide layer on the silicon substrate surface. Combined with the subsequent second wet removal process, the removal efficiency of the first oxide layer and the tunneling layer can be improved. Furthermore, the Cl- in HCl... - The complexation of ions can remove metal ions adhering to the surface of a silicon substrate.
[0017] In some implementations, the first surface also has an oxide layer, the material of which is silicon oxide, located on the surface of the amorphous silicon layer away from the tunneling layer. Before removing the amorphous silicon layer from the silicon substrate, the silicon substrate treatment method further includes removing the oxide layer using a chain-type single-sided removal device. The etchant used to remove the oxide layer is an acidic solution containing HF. The oxide layer covering the amorphous silicon layer reacts very slowly with the alkaline solution of the first wet removal process. Therefore, removing the oxide layer on the amorphous silicon layer beforehand facilitates the rapid and efficient removal of the amorphous silicon layer in the subsequent first wet removal process.
[0018] In some implementations, keeping the silicon substrate from which the amorphous silicon layer has been removed constantly moist includes spraying water onto the silicon substrate. Spraying water onto the silicon substrate during the transfer from one process to another can prevent the silicon substrate from drying out and prevent impurities and dirt carried by the silicon substrate from drying and solidifying on the surface of the silicon substrate.
[0019] In some implementations, after removing the amorphous silicon layer around the silicon substrate and before removing the first oxide layer and the tunneling layer, the silicon substrate processing method further includes: keeping the silicon substrate with the amorphous silicon layer removed constantly moist, and transporting the silicon substrate using a basket, roller conveyor, or tracked conveyor. When using a roller conveyor or tracked conveyor to transport the silicon substrate, each silicon substrate can be transported in real time without waiting, thereby reducing the time the silicon substrate is exposed to air and facilitating the maintenance of a moist state for the silicon substrate.
[0020] In some implementations, the equipment for the second wet removal process described above is an immersion etching tank. This allows for convenient removal of oxides from the first, second, and side surfaces of the silicon substrate. Furthermore, compared to the larger size and floor space required by chain-type equipment, using an immersion etching tank reduces the footprint and improves production efficiency.
[0021] In some implementations, removing the first oxide layer and the tunneling layer includes: etching the silicon substrate using a second acidic solution and / or an ozone aqueous solution to remove the first oxide layer and the tunneling layer; wherein the second acidic solution contains HF; the ozone aqueous solution has an ozone concentration greater than 10 ppm and a pH value of 2-4; and the ozone aqueous solution contains 0.1 wt% to 3 wt% HCl. Both the second acidic solution and the ozone aqueous solution can effectively remove the first oxide layer and the tunneling layer. When etching the silicon substrate using a second acidic solution and an ozone aqueous solution, the removal efficiency of the first oxide layer and the tunneling layer can be improved, thus improving the quality of the silicon substrate.
[0022] In some implementations, the second surface has a second oxide layer. The second oxide layer is removed simultaneously with the first oxide layer and the tunneling layer using a second wet etching process. In this case, an immersion etching tank can remove multiple layers of material, including the first oxide layer, the second oxide layer, and the tunneling layer, in a single process. This eliminates the need for multiple processing steps, thereby improving production efficiency.
[0023] In some implementations, the material of the tunneling layer is one or more of silicon oxide, silicon carbide, aluminum oxide, silicon oxynitride, or silicon oxynitride; the material of the amorphous silicon layer is intrinsic amorphous silicon or doped amorphous silicon; and the material of the first oxide layer is borosilicate glass or phosphosilicate glass.
[0024] In a second aspect, the present invention provides a method for manufacturing a solar cell. This method includes a process for a silicon substrate as described in the first aspect or any implementation thereof.
[0025] The beneficial effects of the solar cell manufacturing method provided in the second aspect can be seen in the beneficial effects of the silicon substrate processing method described in the first aspect or any implementation thereof, and will not be repeated here.
[0026] Thirdly, the present invention provides a solar cell. This solar cell is manufactured using the method for manufacturing a solar cell described in the second aspect.
[0027] The beneficial effects of the solar cell provided in the third aspect can be referred to the beneficial effects of the silicon substrate processing method described in the first aspect or any implementation thereof, and will not be repeated here. Attached Figure Description
[0028] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this invention, illustrate exemplary embodiments of the invention and are used to explain the invention, but do not constitute an undue limitation of the invention. In the drawings:
[0029] Figure 1 This is a schematic diagram of the silicon substrate structure according to an embodiment of the present invention;
[0030] Figure 2 This is a schematic diagram of the process of removing and transporting the amorphous silicon layer on a silicon substrate according to an embodiment of the present invention;
[0031] Figure 3 This is a schematic diagram of the structure of a solar cell according to an embodiment of the present invention.
[0032] Figures 1-3 In the diagram, 10-substrate, 11-doped layer, 12-first oxide layer, 13-tunneling layer, 14-amorphous silicon layer, 15-oxide layer, 16-first passivation layer, 17-antireflection layer, 18-first electrode layer, 21-tunneling layer, 22-doped polycrystalline silicon layer, 221-amorphous silicon layer, 23-second oxide layer, 24-second passivation layer, 25-second electrode layer; 30-roller type single-sided etching equipment, 40-double roller immersion etching tank, 50-basket, 60-spray device; A-first wet removal process, B-first acidic solution cleaning, C-water washing. Detailed Implementation
[0033] To facilitate a clear description of the technical solutions of the embodiments of the present invention, the terms "first" and "second" are used in the embodiments of the present invention to distinguish identical or similar items with essentially the same function and effect. Those skilled in the art will understand that the terms "first" and "second" do not limit the quantity or execution order, and the terms "first" and "second" are not necessarily different.
[0034] It should be noted that in this invention, the terms "exemplary" or "for example" are used to indicate examples, illustrations, or descriptions. Any embodiment or design described as "exemplary" or "for example" in this invention should not be construed as being more preferred or advantageous than other embodiments or designs. Specifically, the use of terms such as "exemplary" or "for example" is intended to present the relevant concepts in a concrete manner.
[0035] In this invention, "at least one" refers to one or more, and "more than one" refers to two or more. "And / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A alone, A and B simultaneously, or B alone, where A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects are in an "or" relationship. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of single or plural items. For example, at least one of a, b, or c can represent: a, b, c, a combination of a and b, a combination of a and c, a combination of b and c, or a, b, and c, where a, b, and c can be single or multiple.
[0036] Tunneling oxide passivated contact (TOPCon) cells are gradually becoming typical high-efficiency solar cells due to their excellent passivation contact performance. TOPCon cells form the passivation contact layer by fabricating a doped polycrystalline silicon layer on the tunneling layer on the back of the silicon wafer. After forming the tunneling layer and the doped polycrystalline silicon layer on the back of the silicon wafer, the wrap-around coatings on the front and sides of the silicon wafer need to be removed to improve the light absorption and appearance of the solar cell's front side.
[0037] Currently, in the industry, the process of fabricating PN junctions and passivation contact structures requires multiple steps to remove the resulting plating and oxide layers. This not only involves numerous steps and high production costs, but also makes it easy for silicon wafers to carry impurities and dirt as they move between these processes. This not only affects the normal operation of subsequent processes but is also difficult to remove, impacting the quality and efficiency of solar cells.
[0038] To address the aforementioned technical problems, embodiments of the present invention provide a method for processing a silicon substrate. This method for processing a silicon substrate includes the following steps:
[0039] Step S100: Provide a silicon substrate. For example... Figure 1 As shown, the silicon substrate has a first side and a second side opposite to each other; the first side has a first oxide layer 12, a tunneling layer 13 formed by a coating process, and an amorphous silicon layer 14 stacked together.
[0040] Specifically, the aforementioned silicon substrate is used to fabricate solar cells. The silicon substrate includes a substrate 10, a doped layer 11, a first oxide layer 12, a tunneling layer 13, an amorphous silicon layer 14, an oxide layer 15, a tunneling layer 21, an amorphous silicon layer 221, and a second oxide layer 23. The substrate 10 has opposing first and second surfaces, and the first and second surfaces of the substrate 10 correspond to the first and second surfaces of the silicon substrate. The first surface of the substrate 10 is the front side of the fabricated solar cell, and the second surface is the back side of the fabricated solar cell. The doped layer 11 is formed on the surface of the first surface of the substrate 10. The first oxide layer 12, the tunneling layer 13, the amorphous silicon layer 14, and the oxide layer 15 are sequentially stacked on the doped layer 11. The tunneling layer 21, the amorphous silicon layer 221, and the second oxide layer 23 are sequentially stacked on the second surface of the substrate 10.
[0041] The tunneling layer 21 and the material surrounding the tunneling layer 13 are the same, namely one or more of silicon oxide, silicon carbide, aluminum oxide, silicon oxynitride, or silicon oxynitride. The amorphous silicon layer 221 and the material surrounding the amorphous silicon layer 14 are the same, namely intrinsic amorphous silicon or doped amorphous silicon. The material surrounding the second oxide layer 23 and the material surrounding the oxide layer 15 are the same, namely borosilicate glass or phosphosilicate glass. The material of the first oxide layer 12 is borosilicate glass or phosphosilicate glass, and the doping type of the first oxide layer 12 is opposite to that of the second oxide layer 23.
[0042] The method for fabricating the silicon substrate described above includes: Step S101: Providing a substrate 10. The substrate 10 can be an n-type semiconductor substrate 10 or a p-type semiconductor substrate 10. The material of the substrate 10 can be monocrystalline silicon or polycrystalline silicon. The fabrication method of the silicon substrate is described below using an n-type silicon substrate 10 as an example.
[0043] Step S102: Texture the substrate 10. Specifically, the texture treatment can be performed on one side of the substrate 10 or on both sides. For example, the texture treatment can be performed on both sides of the substrate 10 using an alkaline solution with additives, forming a pyramid-shaped textured surface on the first and second sides of the substrate 10. This textured surface can trap light, reducing the reflection of sunlight by the solar cell and thus improving the performance of the solar cell. Of course, the texture treatment step can also be omitted.
[0044] Step S103: The first surface of the substrate 10 is doped to form a doped layer 11 and a first oxide layer 12. The doped layer 11 can be n-type or p-type doped. The dopant source for the doped layer 11 can be a Group VA element such as phosphorus, arsenic, bismuth, and antimony, or a Group IIIA element such as boron, aluminum, gallium, and indium. During the formation of the doped layer 11, the first oxide layer 12 is formed on the doped layer 11 due to the participation of oxygen. When the dopant source is boron, the material of the first oxide layer 12 is boron-containing silicon oxide (BSG). When the dopant source is phosphorus, the material of the first oxide layer 12 is phosphorus-containing silicon oxide (PSG). The doping process can be performed using any one of the following: thermal diffusion process, ion implantation process, or dopant source coating and propagation process.
[0045] It should be understood that during the doping process, a wrap-around coating will be formed on the second side of the substrate 10. Before forming the tunneling layer 21, the wrap-around coating on the second side of the substrate 10 needs to be removed using a single-sided removal process, and the textured surface of the second side needs to be polished to make the second side of the substrate 10 smooth, which facilitates the formation of the passivation contact structure.
[0046] Step S104: Form a tunneling layer 21 on the second surface of the substrate 10. At this time, during the formation of the tunneling layer 21, the material of the tunneling layer 21 will form a tunneling layer 13 around the second surface of the substrate 10, that is, the first oxide layer 12.
[0047] The tunneling layer 21 can generate a tunneling effect, allowing majority carriers to pass through while hindering minority carriers. The tunneling layer 21 can also serve to prevent dopants in the doped polysilicon layer 22 from diffusing into the silicon wafer. The tunneling layer 21 can comprise various materials through which majority carriers can tunnel, such as oxides, nitrides, semiconductors, and conductive polymers. The material of the tunneling layer 21 can be silicon oxide, silicon carbide, aluminum oxide, silicon oxynitride, or silicon oxynitride, etc.
[0048] The process for forming the tunneling layer 21 can be physical vapor deposition (PVD), or chemical vapor deposition (CVD) such as atmospheric pressure chemical vapor deposition (APCVD), low pressure chemical vapor deposition (LPCVD), or plasma chemical vapor deposition (PECVD). When the tunneling layer 21 is a silicon oxide layer, the process for forming the tunneling layer 21 can also be thermal oxidation or chemical oxidation. After forming a thin tunneling layer 21, heat treatment can be used to increase the thickness and density of the tunneling layer 21. In practical applications, the pressure during the formation of the tunneling layer 21 can be set lower than atmospheric pressure to reduce the growth rate of the tunneling layer 21. For example, when forming the tunneling layer 21 using thermal oxidation, the working pressure can be set lower than atmospheric pressure. In this case, although the working temperature of the thermal oxidation process is relatively high (600°C or higher), the lower working pressure allows the tunneling layer 21 to maintain a low growth rate, which can significantly reduce the thickness of the tunneling layer 21. Specifically, the working temperature of the thermal oxidation process can be set to 600℃~800℃, and the working pressure can be set to 600 Torr or lower to effectively control the thickness of the tunnel layer 21.
[0049] The deposition process or thermal oxidation process for forming the tunneling layer 21 described above can be carried out in a deposition apparatus. Given the requirement for a low-pressure environment in the formation of the tunneling layer 21, it can be fabricated in a low-pressure chemical vapor deposition apparatus.
[0050] Step S105: An amorphous silicon layer 221 is formed on the tunneling layer 21. During the formation of the amorphous silicon layer 221, a second oxide layer 23 is formed on the amorphous silicon layer 221 due to the presence of oxygen. During this process, a layer 14 surrounding the amorphous silicon layer 14 and a layer 15 surrounding the oxide layer 15 are formed on the first side of the substrate 10 (around the tunneling layer 13).
[0051] The aforementioned amorphous silicon layer 221 can be an intrinsic amorphous silicon layer or a doped amorphous silicon layer. The doping type of this doped amorphous silicon layer is different from that of the doped layer 11. The process for forming the amorphous silicon layer 221 can be physical vapor deposition (PVD), low-pressure chemical vapor deposition (LPCVD), or plasma-enhanced chemical vapor deposition (PECVD), etc. When the amorphous silicon layer 221 is a doped amorphous silicon layer, it can be fabricated using in-situ doping. The equipment for forming the amorphous silicon layer 221 can be an LPCVD apparatus. In this case, the tunneling layer 21 and the amorphous silicon layer 221 can be formed continuously using the same LPCVD apparatus. In this situation, completing two processes using the same apparatus simplifies the process flow, reduces manufacturing time, and lowers manufacturing costs.
[0052] When forming the tunneling layer 21 and the amorphous silicon layer 221 using an LPCVD apparatus, the temperature difference between the operating temperature for forming the tunneling layer 21 and the operating temperature for forming the amorphous silicon layer 221 can be set within the range of 0°C to 200°C. Preferably, this temperature difference can be within the range of 0°C to 100°C. In this case, the temperature difference between the two processes is small, which reduces the time required to change the operating temperature, thereby further improving the efficiency of continuously forming the tunneling layer 21 and the amorphous silicon layer 221. Furthermore, when the temperature difference is small, the changes in the two process parameters are smaller, making it easier to maintain the relatively difficult-to-control temperature.
[0053] Step S200: As Figure 2 As shown, the amorphous silicon layer 14 around the silicon substrate is removed using the first wet removal process A. During the removal of the amorphous silicon layer 14 around the first side of the silicon substrate, the second oxide layer 23 located on the second side of the silicon substrate can protect the tunneling layer 21, the amorphous silicon layer 221, and other structures on the second side.
[0054] The equipment for the first wet removal process A described above can be a chain-type single-sided removal device or an immersion etching tank. The chain-type single-sided removal device is selected from roller-type single-sided etching equipment 30 and track-type single-sided etching equipment. In this case, the chain-type single-sided removal device can perform single-sided processing on the silicon substrate, removing only the amorphous silicon layer 14 around the first side of the silicon substrate, without processing the second side, thus better protecting the functional structure of the second side of the silicon substrate. Since the back side of the silicon substrate is protected by a second oxide layer 23, an immersion etching tank can be used to remove the amorphous silicon layer 14.
[0055] The etchant in the first wet removal process A described above can be an alkaline solution, which includes at least one of KOH, NaOH, or an organic alkaline reagent. In this case, the alkaline solution can chemically react with the amorphous silicon material, thereby removing the layer 14 surrounding the amorphous silicon. Simultaneously, the alkaline solution does not react with oxide materials, or reacts very slowly with oxide materials, thus avoiding damage to the pn junction and functional structure of the first and second surfaces of the silicon substrate by the first wet removal process A. Compared with acidic etchants such as nitric acid, alkaline solutions are not only cheaper but also have lower wastewater treatment costs, which can reduce production costs.
[0056] For example, such as Figure 2As shown, the roller-type single-sided etching apparatus 30 includes one or more tanks, each containing an alkaline etchant. During the removal of the amorphous silicon layer 14 using the roller-type single-sided etching apparatus 30, the first side of the silicon substrate faces the tank, and the amorphous silicon layer 14 is in contact with the etchant surface in the tank. The amorphous silicon layer 14 remains in contact with the etchant as it passes through the tank, thus removing the amorphous silicon layer 14 without damaging the semiconductor structure on the back side of the silicon substrate. Preferably, water can also be sprayed onto the back side of the silicon substrate using a water film device to form a water film, thereby protecting the back side of the silicon substrate.
[0057] like Figure 2 As shown, after the first wet removal process A, the silicon substrate can be washed with water. Water washing C can be performed using a dual-roller immersion etching tank 40. At this time, water washing C can remove residual alkaline etching agent from the silicon substrate surface, thereby preventing residual alkaline solution from interfering with the subsequent second wet removal process and ensuring the quality of the second wet removal process.
[0058] like Figure 2 As shown, after rinsing the silicon substrate with water, the silicon substrate with the amorphous silicon layer removed can be kept constantly moist. The silicon substrate B is cleaned with a first acidic solution, followed by a water rinse. The first acidic solution may contain HCl. The first acidic solution may also contain HCl and HF. The equipment for cleaning the silicon substrate is an immersion etching tank, such as a dual-roller immersion etching tank 40. The equipment for rinsing C can also be a dual-roller immersion etching tank 40.
[0059] When the first acidic solution contains HCl, HCl can neutralize the alkaline solution residue on the silicon substrate surface, thus facilitating the cleaning of the residue. When the first acidic solution contains both HCl and HF, the chemical reaction between HF and silicon oxide can be used to etch the tunneling layer 13 and the first oxide layer 12 on the silicon substrate surface. Combined with the subsequent second wet removal process, the removal efficiency of the first oxide layer 12 and the tunneling layer 13 can be improved. Furthermore, the Cl- in HCl... - The complexation of ions can remove metal ions adhering to the surface of a silicon substrate.
[0060] It should be understood that the material of the aforementioned oxide layer 15 is silicon oxide, located on the surface of the amorphous silicon layer 14 away from the tunneling layer 13. Before removing the amorphous silicon layer 14, the oxide layer 15 can also be removed using a chain-type single-sided removal device. The etchant used to remove the oxide layer 15 is an acidic solution containing HF. The oxide layer 15 covering the amorphous silicon layer 14 reacts very slowly with the alkaline solution of the first wet removal process A. Therefore, removing the oxide layer 15 on the amorphous silicon layer 14 beforehand facilitates the rapid and efficient removal of the amorphous silicon layer 14 by the subsequent first wet removal process A.
[0061] Step S300: Keep the silicon substrate around the amorphous silicon layer constantly wet, and remove the first oxide layer 12 and the tunneling layer 13 using the second wet removal process.
[0062] After removing the amorphous silicon layer 14 and before removing the first oxide layer 12 and the tunneling layer 13, the silicon substrate from which the amorphous silicon layer has been removed can be kept moist by using a basket 50, a roller conveyor, or a tracked conveyor to transport the silicon substrate. When using a roller conveyor or a tracked conveyor to transport the silicon substrate, each silicon substrate can be transported in real time without waiting, thereby reducing the time the silicon substrate is exposed to air and facilitating the maintenance of a moist state. For example, as shown... Figure 2 As shown, when the silicon substrate is transferred using the basket 50, the silicon wafer is transferred into the basket 50 by the rollers of the double roller immersion etching tank 40 (the silicon substrate is located between the upper and lower rollers). After the basket 50 is full of silicon substrate, the basket 50 carries the silicon substrate and transfers it to the equipment of the second wet removal process.
[0063] like Figure 2 As shown, methods to keep the silicon substrate from drying out include spraying water onto the silicon substrate. Spraying water onto the silicon substrate during the transfer from one process to another prevents it from drying out and avoids impurities and contaminants from drying and solidifying on its surface. For example, when using baskets 50 to transfer silicon substrates, each basket 50 holds 400 silicon substrates, and filling a basket 50 takes 6-10 minutes. The silicon substrates that enter the basket 50 first are prone to drying out during this process. A spray device 60 can be installed above or around the basket 50 to spray water onto it, ensuring that the silicon substrates in the basket 50 remain moist.
[0064] The equipment for the aforementioned second wet removal process can be an immersion etching tank. This allows for convenient removal of oxides from the first, second, and side surfaces of the silicon substrate. Furthermore, compared to the larger size and floor space required by chain-type equipment, using an immersion etching tank reduces the footprint and improves production efficiency. This immersion etching tank can be a single tank structure or a dual-roller immersion etching tank. When using a single tank structure, a basket can be used to transport the silicon substrate, and then the basket is placed into the etching tank to complete the second wet removal process. When using a dual-roller immersion etching tank, a roller conveyor belt can be used to transport the silicon substrate between the upper and lower rollers in the dual-roller immersion etching tank for the second wet removal process.
[0065] Removing the first oxide layer 12 and the tunneling layer 13 includes etching the silicon substrate using a second acidic solution and / or an ozone aqueous solution to remove the first oxide layer 12 and the tunneling layer 13. In practical applications, the silicon substrate can be etched using only the second acidic solution, or only the ozone aqueous solution, or sequentially using both the second acidic solution and the ozone aqueous solution. It should be understood that both the second acidic solution and the ozone aqueous solution are placed separately in immersion etching tanks. That is, the number of immersion etching tanks can be one or two.
[0066] The aforementioned second acidic solution contains HF. The ozone aqueous solution has an ozone concentration greater than 10 ppm and a pH value of 2-4; the ozone aqueous solution contains 0.1 wt% to 3 wt% HCl. For example, the ozone concentration of the ozone aqueous solution can be 10 ppm, 15 ppm, 20 ppm, 25 ppm, 30 ppm, 50 ppm, etc. The pH of the ozone aqueous solution can be 2, 2.5, 3, 3.5, 4, etc. The HCl content of the ozone aqueous solution can be 0.1 wt%, 0.5 wt%, 1 wt%, 1.2 wt%, 1.5 wt%, 2 wt%, 2.5 wt%, 3 wt%, etc. Both the second acidic solution and the ozone aqueous solution can effectively remove the first oxide layer 12 and the tunneling layer 13. When using the second acidic solution and the ozone aqueous solution to etch the silicon substrate, the removal efficiency of the first oxide layer 12 and the tunneling layer 13 can be improved, thus improving the quality of the silicon substrate.
[0067] It should be understood that while removing the first oxide layer 12 and the tunneling layer 13 using the second wet removal process, the second oxide layer 23 can also be removed simultaneously. In this case, an immersion etching tank can remove multiple layers of material, including the first oxide layer 12, the second oxide layer 23, and the tunneling layer 13, in a single process. This eliminates the need for multiple steps, thereby improving production efficiency.
[0068] After removing the first oxide layer 12 and the tunneling layer 13, the silicon substrate can be washed with water and then dried.
[0069] In summary, during the removal of the amorphous silicon layer 14 using the first wet removal process A, the removal of the first oxide layer 12 and the tunneling layer 13 using the second wet removal process, and between the first and second wet removal processes, the silicon substrate for which the amorphous silicon layer is being removed is kept constantly moist. At this time, the surface of the silicon substrate has a significant amount of moisture. After the amorphous silicon layer 14 is removed using the first wet removal process A, when the silicon substrate carries impurities and contaminants, these impurities and contaminants mix with the moisture on the silicon substrate surface and remain in a free state. This prevents the impurities and contaminants from drying and firmly adhering to the silicon substrate surface. In subsequent second wet removal processes or other cleaning processes, the free and moist impurities and contaminants can be easily washed away and cleaned. Therefore, keeping the silicon substrate for which the amorphous silicon layer is being removed constantly moist during the silicon substrate processing facilitates the cleaning of impurities and contaminants on the silicon substrate surface, thereby improving the cleanliness of the silicon substrate, the processing efficiency, and the quality of the silicon substrate.
[0070] Compared to existing technologies that involve HF cleaning, water washing, and drying between the first wet removal process A and the second wet removal process, the silicon substrate treatment method of the present invention, on the one hand, omits the HF cleaning, water washing, and drying steps, resulting in a simpler process and lower production costs. On the other hand, it avoids the situation where impurities and dirt dried during the drying process firmly adhere to the silicon substrate, making it easier to clean impurities and dirt from the silicon substrate surface.
[0071] This invention also provides a method for manufacturing a solar cell. The method for manufacturing a solar cell includes the above-described method for processing a silicon substrate. Of course, the method for manufacturing a solar cell may further include the following steps:
[0072] Step A: The amorphous silicon layer 221 on the second surface of the silicon substrate is processed to form a doped polycrystalline silicon layer 22. During this process, the amorphous silicon material is transformed into polycrystalline silicon. Furthermore, tunneling pinholes are formed in the tunneling layer 21, which facilitates better carrier transport while maintaining passivation.
[0073] When the amorphous silicon layer 221 is an intrinsic amorphous silicon layer, it is subjected to doping annealing to form a doped polycrystalline silicon layer 22. The conductivity type of the doped polycrystalline silicon is opposite to that of the doped layer 11. When the amorphous silicon layer 221 is a doped amorphous silicon layer, it is subjected to annealing to form a doped polycrystalline silicon layer 22.
[0074] In practical applications, in order to ensure that amorphous semiconductor materials are transformed into polycrystalline semiconductor materials, the annealing temperature can be 700℃-900℃.
[0075] Step B: Passivate the first positive surface of the silicon substrate to form a first passivation layer 16; form an anti-reflection layer 17 on the first passivation layer 16. Passivate the second surface of the silicon substrate to form a second passivation layer 24.
[0076] The materials of the first passivation layer 16 and the second passivation layer 24 can be selected from one or more of silicon nitride, silicon oxide, silicon oxynitride, aluminum oxide, silicon carbide, and amorphous silicon. The first passivation layer 16 and the second passivation layer 24 can be made of the same material or different materials.
[0077] The process for forming the first passivation layer 16 and the second passivation layer 24 can be one of enhanced plasma chemical vapor deposition, atomic layer deposition, spin coating, screen printing, or spray coating. In practical applications, the first passivation layer 16 and the antireflection layer 17 can be formed first, followed by the second passivation layer 24, or the second passivation layer 24 can be formed first, followed by the first passivation layer 16 and the antireflection layer 17.
[0078] Step C: A first electrode layer 18 is formed on a first surface of the silicon substrate, and the first electrode layer 18 is in electrical contact with the doped layer 11. A second electrode layer 25 is formed on a second surface of the silicon substrate, and the second electrode layer 25 is in electrical contact with the doped polycrystalline silicon layer 22. The materials of the first electrode layer 18 and the second electrode layer 25 can both be selected from one or more of silver, copper, aluminum, nickel, titanium, tungsten, and tin.
[0079] In practical applications, one or more of the following processes can be used to form the first electrode layer 18 and the second electrode layer 25: PVD, screen printing, electroplating, electroless plating, laser transfer, and spraying. Specifically, an opening can first be formed on the first passivation layer 16 and the second passivation layer 24 using a patterning process, and then the first electrode layer 18 and the second electrode layer 25 can be formed within the opening. This patterning process can be laser ablation, etchant etching, photolithography, etc.
[0080] For example, electrode paste can be coated onto the first passivation layer 16 and the second passivation layer 24 using screen printing and heat treatment (burn-through or laser sintering contact) to form the first electrode and the second electrode. During this process, the glass frit in the electrode paste melts and etches the first passivation layer 16 and the second passivation layer 24, naturally forming openings. Metallic silver in the silver electrode paste dissolves in the glass frit and diffuses through these openings. Upon cooling, the solubility of metallic silver in the melt decreases, and silver nanocrystals precipitate from the glass matrix.
[0081] This invention also provides a solar cell. This solar cell is manufactured using the aforementioned method for manufacturing solar cells. For example... Figure 3As shown, the solar cell includes a substrate 10, and a doped layer 11, a first passivation layer 16, an antireflection layer 17, and a first electrode layer 18 located on the front side of the substrate 10, and a tunneling layer 21, a doped polycrystalline silicon layer 22, a second passivation layer 24, and a second electrode layer 25 located on the back side of the substrate 10. The first electrode layer 18 is in electrical contact with the doped layer 11, and the second electrode layer 25 is in electrical contact with the doped polycrystalline silicon layer 22.
[0082] Although the invention has been described herein in conjunction with various embodiments, those skilled in the art will understand and implement other variations of the disclosed embodiments by reviewing the accompanying drawings, the disclosure, and the appended claims in carrying out the claimed invention. In the claims, the word "comprising" does not exclude other components or steps, and "a" or "an" does not exclude a plurality. While different dependent claims may recite certain measures, this does not mean that these measures cannot be combined to produce good results.
[0083] Although the invention has been described in conjunction with specific features and embodiments, it is obvious that various modifications and combinations can be made therein without departing from the spirit and scope of the invention. Accordingly, this specification and drawings are merely exemplary descriptions of the invention as defined by the appended claims, and are considered to cover any and all modifications, variations, combinations, or equivalents within the scope of the invention. Clearly, those skilled in the art can make various alterations and modifications to the invention without departing from its spirit and scope. Thus, if such modifications and modifications of the invention fall within the scope of the claims and their equivalents, the invention is also intended to include such modifications and modifications.
Claims
1. A method for processing a silicon substrate, characterized in that, Includes the following steps: A silicon substrate is provided, the silicon substrate having a first side and a second side opposite to each other; the first side has a first oxide layer, a tunneling layer formed by a coating process, and an amorphous silicon layer stacked together; The amorphous silicon layer around the silicon substrate is removed using a first wet removal process; The silicon substrate around which the amorphous silicon layer is removed is kept constantly wet, and the first oxide layer and the tunneling layer are removed using a second wet removal process. The method of keeping the silicon substrate from which the amorphous silicon layer has been removed always wet includes spraying water onto the silicon substrate.
2. The method for processing a silicon substrate according to claim 1, characterized in that, The equipment for the first wet removal process is a chain-type single-sided removal equipment, which is selected from roller-type single-sided etching equipment and track-type single-sided etching equipment. Alternatively, the equipment for the first wet removal process is an immersion etching tank.
3. The method for processing a silicon substrate according to claim 1, characterized in that, The etching agent in the first wet removal process is an alkaline solution, wherein the alkaline solution includes at least one of KOH, NaOH, or an organic base.
4. The method for processing a silicon substrate according to claim 1, characterized in that, After removing the amorphous silicon layer around the silicon substrate and before removing the first oxide layer and the tunneling layer around the silicon substrate, the silicon substrate treatment method further includes washing the silicon substrate with water.
5. The method for processing a silicon substrate according to claim 1, characterized in that, After removing the amorphous silicon layer around the silicon substrate and before removing the first oxide layer and the tunneling layer around the silicon substrate, the silicon substrate treatment method further includes: keeping the silicon substrate from which the amorphous silicon layer has been removed always in a wet state, cleaning the silicon substrate with a first acidic solution, and then washing the silicon substrate with water. The first acidic solution contains HCl, or the first acidic solution contains HCl and HF; the equipment for cleaning the silicon substrate is an immersion etching tank.
6. The method for processing a silicon substrate according to claim 1, characterized in that, The first surface also has an oxide layer, the material of which is silicon oxide, located on the surface of the amorphous silicon layer away from the tunneling layer; Before removing the amorphous silicon layer around the silicon substrate, the silicon substrate processing method further includes: removing the oxide layer around the silicon substrate using a chain-type single-sided removal device; wherein the etchant used to remove the oxide layer around the silicon substrate is an acidic solution containing HF.
7. The method for processing a silicon substrate according to any one of claims 1 to 6, characterized in that, The equipment for the second wet removal process is an immersion etching tank; And / or, Removing the first oxide layer and the tunneling layer includes: etching the silicon substrate with a second acidic solution and / or etching the silicon substrate with an ozone aqueous solution to remove the first oxide layer and the tunneling layer; wherein the second acidic solution contains HF; the ozone aqueous solution has an ozone concentration greater than 10 ppm and a pH value of 2-4; and the ozone aqueous solution contains 0.1 wt% to 3 wt% HCl.
8. The method for processing a silicon substrate according to any one of claims 1 to 6, characterized in that, The second surface has a second oxide layer. The second oxide layer is removed at the same time as the first oxide layer and the tunneling layer are removed by a second wet removal process.
9. The method for processing a silicon substrate according to any one of claims 1 to 6, characterized in that, The material of the tunneling layer is one or more of silicon oxide, silicon carbide, aluminum oxide, silicon oxynitride, or silicon oxynitride; the material of the amorphous silicon layer is intrinsic amorphous silicon or doped amorphous silicon; the material of the first oxide layer is borosilicate glass or phosphosilicate glass.
10. A method for manufacturing a solar cell, characterized in that, The method of processing the silicon substrate as described in any one of claims 1 to 9.
Citation Information
Patent Citations
CN104051564A
CN112349584A