Mask preparation method and application thereof

Abstract

The invention belongs to the field of solar cells, and provides a preparation method and application of a mask. The method comprises the following steps: providing a silicon-containing substrate; performing first laser processing on the surface of one side of the silicon-containing substrate to form a first patterned mask layer; performing first wet etching on the object obtained after the first laser processing so as to etch a non-patterned mask layer area; performing first removal treatment of a first patterned mask layer on an object obtained after the first wet etching; and carrying out second laser processing on the region in which the patterned mask layer is removed to obtain a second patterned mask layer. According to the method provided by the invention, large-depth etching of the silicon-containing substrate can be realized through two times of laser treatment, the process is simple, other processes are not needed, and the cost of the mask can be reduced.

Description

Technical Field

[0001] This application relates to the technical field of solar cells, and in particular, to a method for preparing a mask and its application. Background Art

[0002] In order to obtain a higher photoelectric conversion efficiency of solar cells, it is necessary to design solar cells with complex structures. For example, in the production process of crystalline silicon cells, a mask process is often used, that is, before a certain process, a mask layer needs to be prepared in a specific area (the area where this process is not required) for protection, and then the mask is removed.

[0003] However, the current mask layer has limited protection ability. After etching under certain conditions, the mask layer will be etched through and lose its protection ability. Therefore, there is an urgent need for a method to achieve etching with a greater depth.

[0004] It should be noted that the above content is not necessarily prior art and does not limit the patent protection scope of this application. Summary of the Invention

[0005] Embodiments of this application provide a method for preparing a mask and its application to solve or alleviate the technical problem that the protection ability of the oxide layer is limited, and the mask will be etched through and lose its protection ability after etching under certain conditions.

[0006] In the first aspect of the embodiments of this application, a method for preparing a mask is proposed, including the following steps: providing a silicon-containing substrate; Performing a first laser treatment on one surface of the silicon-containing substrate to form a first patterned mask layer; performing a first wet etching on the product obtained after the first laser treatment so that the area of the first patterned mask layer is etched; performing a first removal treatment on the product obtained after the first wet etching to remove the first patterned mask layer; performing a second laser treatment on the area where the first patterned mask layer is removed to obtain a second patterned mask layer.

[0007] The method of this application can achieve deep etching of specific areas on a silicon substrate through two laser treatments, thereby enabling the specific areas to have a stronger ability to resist etching. In addition, this process is simple to operate and does not require the assistance of other processes, reducing the cost of the mask.

[0008] Specifically, the first laser treatment can form a first patterned mask layer on the surface of the silicon-containing substrate. By performing wet etching on the non-first-patterned mask layer region, the deep etching of the first silicon-containing substrate is completed. After the first patterned mask layer is removed, the second laser treatment is used to irradiate the region where the first patterned mask layer is removed to form a second patterned mask layer in this region. The second patterned mask layer can provide secondary protection for some regions of the silicon-containing substrate, so that subsequent etching and other operations can be performed in the non-second-patterned mask layer region to obtain the required etching depth (the second deep etching). At the same time, the two laser treatments are carried out in an air atmosphere without additional oxygen-rich conditions, reducing the process conditions for forming the mask.

[0009] According to an embodiment of the present application, the method further includes: performing a second wet etching on the product obtained after the second laser treatment, so that the non-second-patterned mask layer region is etched.

[0010] According to an embodiment of the present application, a second removal treatment is performed on the product obtained after the second wet etching to remove the second patterned mask layer.

[0011] According to an embodiment of the present application, the conditions of the first laser treatment and the second laser treatment independently include: the frequency of the laser is 300 - 800 kHz; the power of the laser is 15 - 60 w.

[0012] According to an embodiment of the present application, the conditions of the first wet etching include: performing it in an alkali solution with a mass fraction of 5% - 30%.

[0013] According to an embodiment of the present application, the first removal treatment is performed in an acidic solution.

[0014] According to an embodiment of the present application, the acidic solution includes a hydrofluoric acid solution with a mass fraction of 3% - 15%.

[0015] According to an embodiment of the present application, the conditions of the second wet etching include: performing it in an alkali solution with a mass fraction of 5% - 30%.

[0016] According to an embodiment of the present application, the second removal treatment is performed in an acidic solution, and the acidic solution includes a hydrofluoric acid solution with a mass fraction of 3% - 15%.

[0017] In the second aspect of the embodiments of the present application, an application of the method for preparing the mask in the first aspect is provided. The application includes the application in the preparation of solar cells. By using the above-mentioned mask preparation method, a patterned mask in the production process of solar cells is prepared. By preparing the patterned mask (the first patterned mask and the second patterned mask) and combining wet etching in an atmospheric atmosphere, the required etching depth can be obtained, simplifying the process steps and process conditions.

[0018] According to the embodiments of the present application, the solar cell includes a tunnel oxide passivated contact solar cell, a heterojunction solar cell or a back contact solar cell.

[0019] According to the embodiments of the present application, the efficiency of the solar cell is increased by 0.05% - 0.15%. Description of the Drawings

[0020] In the drawings, unless otherwise specified, the same reference numerals throughout the several drawings denote the same or similar components or elements. These drawings are not necessarily drawn to scale. It should be understood that these drawings only depict some embodiments disclosed in the present application and should not be regarded as limiting the scope of the present application.

[0021] Figure 1 is a schematic structural diagram of a silicon-containing substrate after the first laser treatment in some embodiments; Figure 2 is a schematic structural diagram of a silicon-containing substrate after the first laser treatment in some other embodiments; Figure 3 is a schematic structural diagram of a silicon-containing substrate after the first wet etching in some embodiments; Figure 4 is a schematic structural diagram of a silicon-containing substrate after the first removal treatment in some embodiments; Figure 5 is a schematic structural diagram of a silicon-containing substrate after the second laser treatment in some embodiments; Figure 6 is a schematic structural diagram of a silicon-containing substrate after the second wet etching in some embodiments; Figure 7 is a schematic structural diagram of a silicon-containing substrate after the second removal treatment in some embodiments.

[0022] Reference Numerals: 1: First Region; 2: Second Region; 3: Third Region; 4: Silicon-containing Substrate; 5: Second Patterned Mask Layer. Detailed Embodiments

[0023] Embodiments of the present application will be described in detail below, and examples of the embodiments are shown in the accompanying drawings. In the drawings, for clarity, the dimensions of layers, regions, elements, and their relative dimensions may be exaggerated. Wherever the same or similar reference numerals are used throughout, they denote the same or similar elements or elements having the same or similar functions. The embodiments described below by reference to the accompanying drawings are exemplary and are only used to explain the present application and should not be construed as a limitation of the present application. It should be noted that, without conflict, the embodiments in the present application and the features in the embodiments may be combined with each other.

[0024] It should be understood that when an element or layer is referred to as being "on", "adjacent to", "connected to", or "coupled to" another element or layer, it can be directly on, adjacent to, connected to, or coupled to the other element or layer, or there may be intervening elements or layers. In contrast, when an element is referred to as being "directly on", "directly adjacent to", "directly connected to", or "directly coupled to" another element or layer, there are no intervening elements or layers. It should be understood that although the terms first, second, third, etc. may be used to describe various elements, components, regions, layers, and / or portions, these elements, components, regions, layers, and / or portions should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer, or portion from another element, component, region, layer, or portion. Thus, without departing from the teachings of the present application, the first element, component, region, layer, or portion discussed below may be referred to as the second element, component, region, layer, or portion. And when discussing the second element, component, region, layer, or portion, it does not necessarily mean that there is a first element, component, region, layer, or portion in the present application.

[0025] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application and the above accompanying drawings are used to distinguish similar objects and do not necessarily have to be used to describe a specific order or sequence. It should be understood that such terms can be interchanged under appropriate circumstances so that the embodiments of the present application described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or device that comprises a series of steps or units does not necessarily have to be limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products, or devices.

[0026] In the present application, when it comes to a numerical interval (i.e., a numerical range), unless otherwise specified, the distribution of the optional numerical values ​​in the numerical interval is considered to be continuous, and includes the two numerical endpoints (i.e., the minimum and maximum values) of the numerical interval, and each numerical value between the two numerical endpoints. Unless otherwise specified, when the numerical interval only refers to an integer in the numerical interval, it includes the two endpoint integers of the numerical range, and each integer between the two endpoints, which is equivalent to directly listing each integer. When multiple numerical ranges are provided to describe features or characteristics, these numerical ranges can be merged. In other words, unless otherwise specified, the numerical range disclosed in the present application should be understood to include any and all sub-ranges included therein. The "numerical value" in the numerical interval can be any quantitative value, such as a number, a percentage, a ratio, etc. "Numerical interval" allows for broadly including quantitative intervals such as percentage intervals, ratio intervals, and ratio intervals.

[0027] At present, solar cells with special structures are mostly prepared by laser processing, because laser has the advantages of fast speed and high precision. For example, by laser processing on a silicon substrate, a silicon dioxide mask layer is formed on the surface of the silicon substrate. The silicon dioxide mask layer can resist a certain degree of etching, thereby achieving the phenomenon that the non-laser area is alkali-etched while the laser-processed area is not etched, so as to complete the preparation of a special structure. However, the protective ability of this silicon dioxide mask layer is limited. After a certain period of alkali etching, it will be etched through and lose its protective ability.

[0028] Accordingly, in a first aspect of an embodiment of the present application, a method for preparing a mask is proposed, the method comprising the following steps: (1) providing a silicon-containing substrate; (2) performing a first laser treatment on a surface of one side of the silicon-containing substrate to form a first patterned mask layer; (3) performing a first wet etching on the product obtained after the first laser treatment to etch areas other than the first patterned mask layer; (4) performing a first removal treatment on the product obtained after the first wet etching to remove the first patterned mask layer; (5) performing a second laser treatment on the area where the first patterned mask layer is removed to obtain a second patterned mask layer.

[0029] The method of the present application can achieve deep etching of a specific area on a silicon substrate through two laser treatments, thereby making the specific area more resistant to etching. In addition, the process is simple to operate and does not require the use of other processes, thereby reducing the cost of the mask.

[0030] Specifically, the first laser treatment can form a first patterned mask layer on the surface of the silicon-containing substrate. By performing wet etching on the area other than the first patterned mask layer area, the deep etching of the first silicon substrate is completed. After that, after removing the first patterned mask layer, the second laser treatment is used to irradiate the area where the patterned mask layer is removed to form a second patterned mask layer in this area. The second patterned mask layer can provide secondary protection for some areas of the silicon-containing substrate, so as to perform operations such as etching on the area other than the second patterned mask layer area later to obtain the required etching depth. At the same time, the two laser treatments are carried out in an air atmosphere without additional oxygen-rich conditions, reducing the conditions for forming the mask.

[0031] According to an embodiment of the present application, in step (1), a silicon-containing substrate is provided.

[0032] In some embodiments, the silicon-containing substrate includes a silicon wafer or a half-cell during the production of a solar cell.

[0033] As an example, the half-cell during the production of the solar cell is a half-cell with a functional layer, and the functional layer is located on one surface of the silicon wafer. The functional layer includes the doping layer or the amorphous silicon layer.

[0034] According to an embodiment of the present application, in step (2), a first laser treatment is performed on one surface of the silicon-containing substrate to form a first patterned mask layer. In this step, through the first laser treatment, a first patterned mask layer is formed on the surface of the silicon-containing substrate.

[0035] In some embodiments, with reference to Figure 1 and 2 , the surface of the silicon-containing substrate 4 is processed using a laser. According to the radiation area of the laser, the surface of the silicon-containing substrate 4 is divided into three areas, namely the first area 1, the second area 2, and the third area 3. The first area 1 is the overlapping area of the laser spot, the second area 2 is the non-overlapping area of the spot, and the third area 3 is the non-laser area.

[0036] Furthermore, during the first laser treatment, the first patterned mask layer is formed in the first area. In this way, the overlapping of the laser spots can increase the thickness of the first patterned mask layer, so that the first patterned mask layer can better play the role of a mask.

[0037] In some embodiments, the first laser treatment process uses ultraviolet picosecond laser or ultraviolet femtosecond laser.

[0038] Generally, the power and frequency determine the energy density of the laser, and the energy density determines the formation of the oxide layer. When the laser energy density is low, the formed oxide layer is thin or no oxide layer can be formed. When the laser energy density is too high, no oxide layer can be formed, and the laser will directly remove the bottom silicon substrate.

[0039] Optionally, the power of the laser during the first laser treatment process is 15 - 60 w, such as 15 w, 20 w, 45 w, 60 w, etc.

[0040] Optionally, the frequency of the laser during the first laser treatment process is 300 - 800 kHz, such as 300 kHz, 500 kHz, 600 kHz, 800 kHz, etc.

[0041] According to the embodiments of the present application, the thickness of the first patterned mask layer can be adjusted according to the actual process requirements to obtain the process conditions of the first laser treatment.

[0042] As an example, the thickness of the first patterned mask layer is 5 - 30 nm.

[0043] According to the embodiments of the present application, in step (3), the product obtained after the first laser treatment is subjected to a first wet etching so that the regions other than the first patterned mask layer are etched. In this step, in combination with the wet treatment, a certain depth of etching can be obtained on the silicon-containing substrate.

[0044] In some embodiments, referring to Figure 3 , the first wet etching can etch the second region 2 and the third region 3 of the silicon-containing substrate, and the first region 1 (the first patterned mask layer) is retained. Optionally, the first wet etching is carried out using an alkali solution with a mass fraction of 5% - 30%.

[0045] Furthermore, the alkali solution is an aqueous solution of an alkali. The alkali includes at least one of sodium hydroxide and potassium hydroxide.

[0046] In some embodiments, during the first wet etching process, only the second region and the third region are etched, and the first region (the first patterned mask layer) is retained as a mask layer.

[0047] It can be understood that during the wet etching process, when the first patterned mask layer is damaged, the silicon-containing substrate (such as a silicon substrate) at the bottom of the first patterned mask layer will react with the alkali solution to generate bubbles. Therefore, the end point of the first wet etching is that the silicon-containing substrate under the first patterned mask layer region does not react with the alkali.

[0048] According to the embodiments of the present application, the etching depth can be controlled by adjusting the time of the first wet etching according to the actual process design.

[0049] As an example, the etching depth is 50 - 100 nm.

[0050] According to an embodiment of the present application, in step (4), the product obtained after the first wet etching is subjected to a first removal treatment to remove the first patterned mask layer. In this step, during the wet etching process, part of the first patterned mask layer is damaged. Removing the first patterned mask layer facilitates subsequent laser treatment to obtain a deeper etching depth.

[0051] In some embodiments, referring to Figure 4 , the product obtained after the first wet etching is subjected to a first removal treatment of the first patterned mask layer to remove the first patterned mask in the first region 1, such that the first region 1, the second region 2, and the third region 3 are all silicon-containing substrates, but there are height differences among the first region, the second region, and the third region.

[0052] In some embodiments, the first removal treatment is carried out in an acidic solution, and the acidic solution includes a hydrofluoric acid solution with a mass fraction of 3% - 15%.

[0053] According to an embodiment of the present application, in step (5), referring to Figure 5 , the region where the first patterned mask layer is removed is subjected to a second laser treatment to obtain a second patterned mask layer 5. In this step, the second laser treatment can obtain a second patterned mask layer and form it within the first region range of the silicon-containing substrate after the first laser treatment, which is beneficial for subsequent formation of a deeper etching depth on the silicon-containing substrate.

[0054] Optionally, in some embodiments, the second laser treatment process uses an ultraviolet picosecond laser or an ultraviolet femtosecond laser.

[0055] Optionally, during the second laser treatment process, the power of the laser is 15 - 60 w, such as 15 w, 20 w, 45 w, 60 w, etc.

[0056] Optionally, during the second laser treatment process, the frequency of the laser is 300 - 800 kHz, such as 300 kHz, 500 kHz, 600 kHz, 800 kHz, etc.

[0057] According to an embodiment of the present application, the thickness of the second patterned mask layer can be adjusted according to the actual process requirements by adjusting the process conditions of the first laser treatment.

[0058] As an example, the thickness of the second patterned mask layer is 5 - 30 nm.

[0059] In some embodiments, it further includes step (6), referring to Figure 6, the obtained product after the second laser treatment is subjected to a second wet etching to etch the non-second patterned mask layer region. In this step, the second region 2 and the third region 3 formed by the first laser treatment are wet-etched, and the presence of the second patterned mask layer formed in the first region 1 is protected, thereby obtaining a deeper etching depth.

[0060] In some embodiments, the second wet etching can etch the second region and the third region of the silicon-containing substrate, and the first region (the second patterned mask layer) is retained. Optionally, the first wet etching is carried out using an alkali solution with a mass fraction of 5%-30%.

[0061] Furthermore, the alkali solution is an aqueous solution of an alkali. The alkali includes at least one of sodium hydroxide and potassium hydroxide.

[0062] In some embodiments, during the second wet etching process, only the second region and the third region are etched, and the first region (the first patterned mask layer) is retained as a mask layer.

[0063] It can be understood that during the wet etching process, when the second patterned mask layer is damaged, the silicon-containing substrate (such as a silicon substrate) at the bottom of the second patterned mask layer will react with the alkali solution to generate bubbles. Therefore, the end point of the second wet etching is that the silicon-containing substrate under the second patterned mask layer region does not react with the alkali.

[0064] According to the embodiments of the present application, the etching depth can be controlled by controlling the second wet etching time according to the actual process design.

[0065] As an example, the etching depth is 50-100 nm.

[0066] In some embodiments, it further includes step (7) of performing a second removal treatment on the obtained product after the second wet etching for the second patterned mask layer.

[0067] In some embodiments, referring to Figure 7 , a second removal treatment is performed on the obtained product after the second wet etching to remove the second patterned mask layer existing in the first region 1, so that the first region 1, the second region 2, and the third region 3 are all silicon-containing substrates, and there are height differences among the first region, the second region, and the third region.

[0068] In some embodiments, the second removal treatment is carried out in an acidic solution, and the acidic solution includes a hydrofluoric acid solution with a mass fraction of 3%-15%.

[0069] In some embodiments, after the first removal treatment and the second removal treatment, it further includes cleaning and drying the obtained product.

[0070] Optionally, the cleaning is carried out with deionized water. The silicon-containing substrate after cleaning is dried, and the drying temperature is 50 - 150 °C.

[0071] In the second aspect of the embodiments of the present application, there is provided an application of the method for preparing a mask in the first aspect, and the application includes an application in the preparation of a solar cell. By using the above-mentioned mask preparation method, a patterned mask in the production process of a solar cell is prepared. By preparing the patterned mask (the first patterned mask and the second patterned mask) and combining wet etching in an atmospheric atmosphere, the required etching depth can be obtained, simplifying the process steps and process conditions.

[0072] In some embodiments, the solar cell includes a TOPcon cell (tunnel oxide passivated contact solar cell), a heterojunction solar cell, or a back contact solar cell.

[0073] As an example, taking the TOPCon cell as an example: S1: Provide a silicon wafer Texturing and cleaning are performed on an N-type silicon wafer (silicon substrate) with a thickness of 80 - 140 μm, and a uniform "positive pyramid" textured surface with a height of 1 - 3 μm is formed on the opposite two surfaces of the silicon wafer.

[0074] S2: Perform boron doping, edge plating etching, and removal of BSG on the front side of the N-type silicon wafer A boron-doped layer with a thickness of 30 - 150 nm is diffused on the front side of the silicon wafer after texturing and cleaning.

[0075] The boron-doped substrate is subjected to chain pickling with a 5 wt% HF solution.

[0076] The back side of the substrate is etched with a 5 wt% sodium hydroxide solution.

[0077] S3: Form a silicon dioxide tunneling layer on the back side A tunneling oxide layer with a thickness of 1 - 3 nm is formed on the back side of the silicon wafer.

[0078] S4: Phosphorus-doped polysilicon layer A phosphorus-doped polysilicon layer with a thickness of 80 - 400 nm is formed on the side of the tunneling oxide layer away from the silicon wafer.

[0079] S5: Use a 3 - 15% hydrofluoric acid solution to remove the PSG on the back side and perform a first laser treatment on the back side (the power of the laser is 15 - 60 w and the frequency is 300 - 800 kHz) to form a first patterned mask layer (silicon dioxide mask layer) with a thickness of 5 - 20 nm on the surface of the phosphorus-doped polysilicon layer.

[0080] S6: First wet etching treatment The non-first patterned mask layer region is etched using an alkali solution with a mass fraction of 5% - 30%. The etching depth is 50 - 100 nm.

[0081] S7: Pickling A hydrofluoric acid solution with a mass fraction of 3% - 15% is used to remove the first patterned mask layer and simultaneously remove the front curvature.

[0082] S8: Second laser treatment The region of the first patterned mask layer obtained after the first laser treatment is subjected to a second laser treatment to obtain a second patterned mask layer.

[0083] S9: Second wet etching treatment The non-second patterned mask layer region is etched using an alkali solution with a mass fraction of 5% - 30%. The etching depth is 50 - 100 nm.

[0084] S10: Pickling A hydrofluoric acid solution with a mass fraction of 3% - 15% is used to remove the second patterned mask layer.

[0085] S11: Deposit a passivation layer on the front side, and deposit an antireflection layer on both the front and back sides.

[0086] S12: Prepare a first grid electrode in the region where the second patterned mask layer is removed, prepare a second grid electrode on the front side, and perform photo-injection to obtain a TOPcon solar cell.

[0087] In this cell, the first grid electrode is located in the region of the second patterned mask layer. In this way, the thickness of the phosphorus-doped layer at the first grid is relatively thick, and the thickness of the phosphorus-doped layer at non-first grid is relatively thin. This is beneficial for reducing parasitic absorption, increasing the short-circuit current, and thus beneficial for improving the photoelectric conversion efficiency of the solar cell.

[0088] In some embodiments, the photoelectric conversion efficiency of the solar cell is increased by 0.05% - 0.15%.

[0089] Next, exemplary embodiments according to the present application will be described in more detail with reference to the accompanying drawings. It should be noted that these exemplary embodiments can be implemented in many different forms and should not be construed as being limited only to the embodiments described herein.

[0090] Example 1 S1: Provide a silicon wafer The N-type silicon wafer with a thickness of 130 μm is subjected to texturing cleaning to form a uniform "positive pyramid" texture on the opposite two surfaces of the silicon wafer, and the height of the texture is 3 μm.

[0091] S2: Perform boron doping, curvature etching, and removal of BSG on the front side of the N-type silicon wafer Diffuse a boron-doped layer with a thickness of 50 nm on the front side of the silicon wafer after texturing and cleaning.

[0092] Perform chain pickling on the boron-doped substrate with an HF solution having a concentration of 1-10 wt%.

[0093] Etch the back side of the substrate with a sodium hydroxide solution having a concentration of 1-10 wt%.

[0094] S3: Form a silicon dioxide tunneling layer on the back side Form a tunneling oxide layer with a thickness of 1 nm on the back side of the silicon wafer.

[0095] S4: Phosphorus-doped polysilicon layer Form a phosphorus-doped polysilicon layer with a thickness of 300 nm on the side of the tunneling oxide layer away from the silicon wafer.

[0096] S5: Remove the PSG on the back side with a 3-15% hydrofluoric acid solution, and perform a first laser treatment on the back side (laser power: 50 w, frequency: 400 kHz) to form a first patterned mask layer (silicon dioxide mask layer) with a thickness of 20 nm on the surface of the phosphorus-doped polysilicon layer.

[0097] S6: First wet etching treatment Etch the area without the first patterned mask layer with an alkali solution having a mass fraction of 30%. The etching depth is 80 nm.

[0098] S7: Pickling Use a hydrofluoric acid solution with a mass fraction of 15% to remove the first patterned mask layer and simultaneously remove the warp on the front side.

[0099] S8: Second laser treatment Perform a second laser treatment (laser power: 50 w, frequency: 400 kHz) on the area with the first patterned mask layer obtained after the first laser treatment to obtain a second patterned mask layer.

[0100] S9: Second wet etching treatment Etch the area without the second patterned mask layer with an alkali solution having a mass fraction of 20%. The etching depth is 80 nm.

[0101] S10: Pickling Use a hydrofluoric acid solution with a mass fraction of 15% to remove the second patterned mask layer.

[0102] S11: Deposit a passivation layer on the front side, and deposit an antireflection layer on both the front and back sides.

[0103] S12: Prepare a first grid line electrode in the area where the second patterned mask layer is removed, prepare a second grid line electrode on the front side, and perform optical injection to obtain a TOPcon solar cell.

[0104] Comparative Example 1 S1: Provide a silicon wafer Texturing and cleaning of an N-type silicon wafer with a thickness of 130 μm to form a uniform "positive pyramid" textured surface on opposite surfaces of the silicon wafer, and the height of the textured surface is 3 μm.

[0105] S2: Boron doping, warp etching, and removal of BSG on the front side of the N-type silicon wafer Diffuse a boron doping layer with a thickness of 50 nm on the front side of the silicon wafer after texturing and cleaning.

[0106] Use a 5 wt% HF solution to perform chain pickling on the boron-doped substrate.

[0107] Use a 5 wt% sodium hydroxide solution to etch the back side of the substrate.

[0108] S3: Form a silicon dioxide tunneling layer on the back side Form a 1-nm tunneling oxide layer on the back side of the silicon wafer.

[0109] S4: Phosphorus-doped polysilicon layer Form a phosphorus-doped polysilicon layer with a thickness of 300 nm on the side of the tunneling oxide layer away from the silicon wafer.

[0110] S5: Deposit a passivation layer on the front side, and deposit antireflection layers on both the front and back sides.

[0111] S6: Prepare a first grid line electrode on the back side, prepare a second grid line electrode on the front side, and perform light injection to obtain a TOPcon solar cell.

[0112] Test the optoelectronic performance of the above TOPcon solar cell.

[0113] Test of photoelectric conversion efficiency, short-circuit current, open-circuit voltage, and fill factor: The specific test method is to place the cell under simulated sunlight with a light source of 100 mW / cm 2 AM 1.5G at 25 °C and obtain the test results by connecting to a source meter using the four-wire method. It should be noted that the values in the following table are relative values compared with Comparative Example 1.

[0114] Table 1

[0115] As can be obtained from the above table, by adopting the solution of the above embodiment in the present application to prepare the solar cell mask, a patterned mask can be prepared in an air atmosphere, such that the first grid electrode is located in the area of the second patterned mask layer, and the thickness of the phosphorus doping layer at the first grid electrode is relatively thick, while the thickness of the phosphorus doping layer at non-first grid areas is relatively thin. This is beneficial for reducing parasitic absorption and increasing the short-circuit current, and thus is beneficial for improving the photoelectric conversion efficiency of the solar cell.

[0116] It should also be noted that in the present application, "some embodiments", "other embodiments", "embodiments", etc. refer to the specific features, structures or characteristics described in connection with the embodiment being included in at least one embodiment generally described in the present application. The same expression appearing in multiple places in the specification does not necessarily refer to the same embodiment. Further, when describing a specific feature, structure or characteristic in connection with any one embodiment, it is intended that the implementation of such feature, structure or characteristic in combination with other embodiments also falls within the scope of the present application.

[0117] In the above embodiments, the descriptions of the respective embodiments have their own emphases. For parts not detailed in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0118] It should also be noted that the above are only the preferred embodiments of the present application, and do not limit the patent protection scope of the present application accordingly. Any equivalent structure or equivalent process transformation made by using the content of the specification and drawings of the present application, or directly or indirectly applied in other related technical fields, is similarly included in the patent protection scope of the present application.

Claims

1. A method for preparing a mask, characterized in that: The following steps are involved: providing a silicon-containing substrate; Performing a first laser treatment on a surface of one side of the silicon-containing substrate to form a first patterned mask layer; Performing a first wet etching on the product obtained after the first laser treatment, so that the area other than the first patterned mask layer is etched; Performing a first removal treatment on the product obtained by the first wet etching to remove the first patterned mask layer; A second laser treatment is performed on the area where the first patterned mask layer is removed to obtain a second patterned mask layer.

2. The method according to claim 1, characterized in that Also includes: The product obtained after the second laser treatment is subjected to a second wet etching process, so that a region other than the second patterned mask layer is etched.

3. The method according to claim 2, characterized in that Also includes: A second removal process is performed on the product obtained by the second wet etching to remove the second patterned mask layer.

4. The method according to any one of claims 1 to 3, characterized in that: The conditions of the first laser treatment and the second laser treatment respectively and independently include: The frequency is 300-800kHz; the power is 15-60w.

5. The method according to any one of claims 1 to 3, characterized in that: The conditions of the first wet etching include: It is carried out in an alkaline solution with a mass fraction of 5%-30%.

6. The method according to any one of claims 1 to 3, characterized in that: The first removal treatment is carried out in an acidic solution, The acidic solution includes a hydrofluoric acid solution with a mass fraction of 3%-15%.

7. The method according to claim 2, characterized in that The conditions of the second wet etching include: It is carried out in an alkaline solution with a mass fraction of 5%-30%.

8. The method according to claim 3, characterized in that The second removal treatment is carried out in an acidic solution, The acidic solution includes a hydrofluoric acid solution with a mass fraction of 3%-15%.

9. An application of the method according to any one of claims 1 to 8, characterized in that: The applications include applications in the preparation of solar cells.

10. The method according to claim 9, characterized in that The solar cell includes a tunneling oxide passivation contact solar cell, a heterojunction solar cell or a back contact solar cell.

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