Substrate preparation method and photovoltaic cell

Abstract

The application provides a substrate preparation method and a photovoltaic cell, and is used for preparing a substrate including a pyramid structure. The preparation method comprises the following steps: providing a substrate, the substrate having two opposite sides; forming a first adjustment layer on at least one side of the substrate; forming a second adjustment layer with a preset thickness on the side of the first adjustment layer away from the substrate; the second adjustment layer has a plurality of through holes penetrating through the second adjustment layer in the thickness direction; performing a first type etching on the first adjustment layer with the second adjustment layer as a mask, removing the part of the first adjustment layer exposed by the through holes and forming an opening pattern with a preset width value; performing a second type etching on the second adjustment layer and the part of the substrate exposed by the opening pattern, so as to obtain the pyramid structure on the substrate; and removing the remaining first adjustment layer, the remaining substrate and the pyramid structure, which together constitute the substrate. By using the method, the process difficulty is effectively simplified, the preparation cost is reduced, and the higher control precision of the pyramid structure topography parameters is obtained.

Description

TECHNICAL FIELD

[0001] The present application relates to a semiconductor substrate preparation method, in particular to a substrate preparation method and a photovoltaic cell. BACKGROUND

[0002] Forming a texture on the surface of a silicon substrate is an extremely important step in the preparation process of a photovoltaic cell. It mainly prepares a pyramid structure on the surface of the silicon substrate to reduce the reflectivity of the incident light and thus improve the utilization rate of the incident light. It can be understood that the topographic parameters of the aforementioned pyramid structure (such as the formation width, the formation height, etc.) play a crucial role in ensuring and improving the conversion efficiency of the photovoltaic cell.

[0003] In related technologies, a metal copper assisted chemical etching process, a double-beam interference process, and a plasma etching process are usually used to obtain a pyramid structure by removing part of the material in a specific area of the surface of the silicon substrate. However, in related processes, there is a lack of technical means to accurately control the topographic parameters of the pyramid structure, often relying on the personal experience of the technician or the past experimental data to roughly control the topographic parameters of the pyramid structure by adjusting some process parameters; or by preparing a high-precision etching mask, combined with multiple etching to gradually control the topographic parameters of the pyramid structure. Obviously, this not only cannot meet the increasingly stringent performance requirements for the conversion efficiency of the photovoltaic cell, but also is not conducive to improving the production efficiency and reducing the preparation cost.

[0004] Therefore, it is urgent to improve the related process to improve the control accuracy of the topographic parameters of the pyramid structure, so as to ensure and improve the conversion efficiency of the photovoltaic cell, and further reduce the preparation cost. SUMMARY

[0005] In view of the above defects, the present application provides a substrate preparation method for preparing a substrate including a pyramid structure. Through the improvement of the related process, the method effectively simplifies the process difficulty and reduces the preparation cost while obtaining a higher control accuracy of the topographic parameters of the pyramid structure.

[0006] In one aspect, the present application provides a substrate preparation method for preparing a substrate including a pyramid structure, which comprises the following steps:

[0007] providing a substrate, the substrate having two opposite sides;

[0008] forming a first adjustment layer on at least one side of the substrate; the first adjustment layer and the substrate are different in etching selectivity;

[0009] forming a second adjustment layer with a preset thickness value on a side of the first adjustment layer away from the substrate; the second adjustment layer has the same etching selectivity as the substrate; and the second adjustment layer has a plurality of through holes penetrating the second adjustment layer in a thickness direction of the second adjustment layer; the through holes are used to define a number of the pyramid structures to be formed;

[0010] performing a first type of etching on the first adjustment layer using the second adjustment layer as a mask to remove the first adjustment layer exposed by the through holes and form an opening pattern with a preset width value; the opening pattern is used to define a side length of a bottom of the pyramid structure;

[0011] synchronously performing a second type of etching on the second adjustment layer and the substrate exposed by the opening pattern to obtain the pyramid structure on the substrate; wherein the thickness of the second adjustment layer is used to define a height of the pyramid structure to be formed;

[0012] removing the remaining first adjustment layer; and the remaining substrate and the pyramid structure together constitute the substrate.

[0013] The preparation method as described above, wherein the step of forming the second adjustment layer on a side of the first adjustment layer away from the substrate comprises:

[0014] forming the silicon-based thin film by deposition while incorporating oxygen atoms to obtain an oxygen-containing crystalline silicon film with a plurality of through holes; the oxygen-containing crystalline silicon film is used as the second adjustment layer; wherein,

[0015] The porosity of the oxygen-containing crystalline silicon film comprises 60-97%; and the average diameter of the through holes comprises 2 nm-1000 nm.

[0016] The preparation method as described above, wherein the first adjustment layer comprises a SiOx layer, a SiNy layer, a PSG layer or a BSG layer; wherein x and y are positive numbers.

[0017] The second adjustment layer comprises an N-type doped oxygen-containing microcrystalline layer, a P-type doped oxygen-containing microcrystalline layer or an oxygen-containing polycrystalline silicon layer.

[0018] The preparation method as described above, wherein,

[0019] The first type of etching comprises etching the first adjustment layer using an HF solution with a mass percentage content of 0.1wt%-10wt% at a reaction temperature of 25°C-35°C for 0.2min-10min.

[0020] The preparation method as described above, wherein,

[0021] The second type of etching includes: using a mixed solution including 0.1wt%-10wt% of lye and 0.1wt%-10wt% of a texturing additive in mass percentage at a reaction temperature of 50°C-85°C to etch the second adjustment layer and the exposed part of the substrate for the opening pattern for 200s-1000s.

[0022] The preparation method as described above, wherein,

[0023] The thickness of the first adjustment layer includes: 10nm-300nm; the thickness of the second adjustment layer includes: 5nm-300nm; the bottom side length of the pyramid structure includes: 10nm-100nm; the forming height of the pyramid structure includes: 2nm-200nm.

[0024] The preparation method as described above,

[0025] forming a first adjustment layer on at least one side of the substrate, including:

[0026] forming a first adjustment layer on only one side of the substrate;

[0027] correspondingly, the method includes:

[0028] forming a second adjustment layer with a preset thickness value on the side of the first adjustment layer away from the substrate; the second adjustment layer has a plurality of through holes in the thickness direction through itself;

[0029] performing a first type of etching on the first adjustment layer with the second adjustment layer as a mask to form an opening pattern with a preset width value;

[0030] synchronously performing a second type of etching on the second adjustment layer and the exposed part of the substrate for the opening pattern to obtain a pyramid structure on the substrate;

[0031] removing the remaining first adjustment layer; the remaining substrate and the pyramid structure together constitute the substrate.

[0032] The preparation method as described above,

[0033] forming a first adjustment layer on at least one side of the substrate, including:

[0034] forming a first adjustment layer on only one side of the substrate;

[0035] correspondingly, the method includes:

[0036] forming a second adjustment layer with a preset thickness value on the side of the first adjustment layer away from the substrate; the second adjustment layer has a plurality of through holes in the thickness direction through itself;

[0037] performing first-type etching on the first adjustment layer with the second adjustment layer as a mask to form an opening pattern with a preset width value;

[0038] forming a protective layer on the side of the substrate away from the first adjustment layer;

[0039] synchronously performing second-type etching on the second adjustment layer and the exposed part of the substrate to obtain a pyramid structure on the side of the substrate;

[0040] removing the remaining first adjustment layer and the protective layer, and the remaining substrate and the pyramid structure together constitute the substrate.

[0041] The preparation method as described above forms a first adjustment layer on at least one side of the substrate, comprising:

[0042] forming a first adjustment layer on both sides of the substrate;

[0043] Correspondingly, the method comprises:

[0044] forming a second adjustment layer with a preset thickness value on the side of each first adjustment layer away from the substrate; each second adjustment layer has a plurality of through holes in the thickness direction;

[0045] respectively performing first-type etching on the corresponding first adjustment layer with each second adjustment layer as a mask to form an opening pattern penetrating each first adjustment layer;

[0046] synchronously performing second-type etching on each second adjustment layer and the exposed part of the substrate to obtain a pyramid structure on both sides of the substrate;

[0047] removing the remaining first adjustment layer; and the remaining substrate and the pyramid structure together constitute the substrate.

[0048] In another aspect, the application provides a photovoltaic cell, which comprises a substrate prepared by the preparation method as described above, a first functional layer, a second functional layer and an electrode structure; wherein the substrate has opposite two sides; the first functional layer is located on one side of the substrate; the first functional layer is configured to form a PN junction with the substrate; the second functional layer is located on the side of the substrate away from the first functional layer; the second functional layer is configured to constitute a back surface field of the substrate; and the electrode structure is located on the side of the first functional layer and / or the second functional layer away from the substrate.

[0049] The substrate preparation method and the photovoltaic cell provided by the embodiments of the present application form a first adjustment layer on at least one side of the substrate, and form a second adjustment layer with a preset thickness value on the side of the first adjustment layer away from the substrate, the second adjustment layer has a plurality of through holes penetrating through the second adjustment layer in the thickness direction. The etching selectivity of the first adjustment layer is different from that of the substrate, and the etching selectivity of the second adjustment layer is the same as that of the substrate.

[0050] Based on this, the first adjustment layer is etched by taking the second adjustment layer as a mask to selectively remove the exposed part of the first adjustment layer to form an opening pattern, and the opening pattern with a preset width value can be conveniently and accurately controlled by adjusting the etching time and other parameters of the first etching. Then, the second adjustment layer and the exposed part of the substrate are synchronously etched by the second etching to obtain a pyramid structure on the substrate. In this way, the length of the bottom edge of the pyramid structure is conveniently and accurately controlled by means of the opening pattern, and the formation height of the pyramid structure is conveniently and accurately controlled by means of the thickness of the second adjustment layer.

[0051] In this way, the embodiments of the present application effectively improve the control accuracy of the pyramid structure morphology parameters, reduce the reflectivity of the obtained pyramid structure to incident light, and further ensure and improve the conversion efficiency of the photovoltaic cell. Moreover, the process difficulty is effectively simplified and the preparation cost is reduced. BRIEF DESCRIPTION OF DRAWINGS

[0052] Figure 1 A flowchart of a substrate preparation method provided in some embodiments of the present application;

[0053] Figure 2 A flowchart of another substrate preparation method provided in some embodiments of the present application;

[0054] Figure 3 A flowchart of another substrate preparation method provided in some embodiments of the present application;

[0055] Figure 4 A flowchart of another substrate preparation method provided in some embodiments of the present application;

[0056] Figure 5 A structure diagram of a structure obtained after step S10 is performed in some embodiments of the present application;

[0057] Figure 6 A structure diagram of a structure obtained after step S20 is performed, and a structure diagram of a structure obtained after step S20'' is performed in some embodiments of the present application;

[0058] Figure 7 This is a schematic diagram of the structure obtained after executing step S30 and the structure obtained after executing step S30'', provided in some embodiments of this application;

[0059] Figure 8 This is a schematic diagram of the structure obtained after executing step S40 and the structure obtained after executing step S40'', provided in some embodiments of this application.

[0060] Figure 9 for Figure 8 Enlarged view of region A in the middle;

[0061] Figure 10 This is a schematic diagram of the structure obtained after executing step S50 and the structure obtained after executing step S50'', provided in some embodiments of this application.

[0062] Figure 11 This is a schematic diagram of the structure obtained after executing step S60 and the structure obtained after executing step S60', provided in some embodiments of this application.

[0063] Figure 12 This is a schematic diagram of the structure obtained after performing step S20' in some embodiments of this application;

[0064] Figure 13 This is a schematic diagram of the structure obtained after performing step S30' in some embodiments of this application;

[0065] Figure 14 This is a schematic diagram of the structure obtained after performing step S40' in some embodiments of this application;

[0066] Figure 15 This is a schematic diagram of the structure obtained after performing step S50' in some embodiments of this application;

[0067] Figure 16 This is a schematic diagram of the structure obtained after performing step S60' in some embodiments of this application;

[0068] Figure 17 This is a schematic diagram of the structure obtained after performing step S45 in some embodiments of this application;

[0069] Figure 18 This is a schematic diagram of the structure obtained after performing step S50'' in some embodiments of this application;

[0070] Figure 19 This is a schematic diagram of the structure obtained after performing step S60'' in some embodiments of this application;

[0071] Figure 20 A schematic diagram of a structure of a photovoltaic cell provided in some embodiments of the present application.

[0072] Explanation of reference signs:

[0073] 10 - substrate; 20 - first adjustment layer; 30 - second adjustment layer; 40 - protective layer; 50 - first functional layer; 60 - second functional layer; 70 - electrode structure;

[0074] H1 - via hole; H2 - opening pattern; G0 - pyramid structure; G1 - first type of pyramid structure; G2 - second type of pyramid structure. DETAILED DESCRIPTION

[0075] In order to make the objectives, technical solutions and advantages of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below in conjunction with the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the scope of protection of the present application.

[0076] As shown in Figure 1 , the present application provides a substrate preparation method for preparing a substrate including a pyramid structure, comprising the following steps:

[0077] S10, providing a substrate, the substrate having two opposite sides.

[0078] S20, forming a first adjustment layer on at least one side of the substrate; the first adjustment layer and the substrate have different etching selectivities.

[0079] S30, forming a second adjustment layer with a preset thickness value on the side of the first adjustment layer away from the substrate; the second adjustment layer and the substrate have the same etching selectivity; and the second adjustment layer has a plurality of via holes penetrating through itself in the thickness direction of the second adjustment layer; the via holes are used to define the number of pyramid structures to be formed.

[0080] S40, performing a first type of etching on the first adjustment layer with the second adjustment layer as a mask, removing the part of the first adjustment layer exposed by the via holes and forming an opening pattern with a preset width value; the opening pattern is used to define the length of the bottom side of the pyramid structure.

[0081] S50, synchronously performing a second type of etching on the second adjustment layer and the part of the substrate exposed by the opening pattern, to obtain the pyramid structure on the substrate; wherein the thickness of the second adjustment layer is used to define the formation height of the pyramid structure.

[0082] S60, removing the remaining first adjustment layer; the remaining substrate and the pyramid structure together constitute a substrate.

[0083] In the present application, a first adjustment layer is formed on at least one side of the substrate; and a second adjustment layer with a preset thickness value is formed on the side of the first adjustment layer away from the substrate, the second adjustment layer has a plurality of through holes penetrating itself in the thickness direction. Wherein, the first adjustment layer and the substrate are set to have different etching selectivities; and the second adjustment layer and the substrate have the same etching selectivity.

[0084] Based on this, the first adjustment layer is etched by taking the second adjustment layer as a mask to selectively remove the exposed part of the first adjustment layer to form an opening pattern, and the etching time of the first etching is adjusted to accurately control the opening pattern to have a preset width value; then, the second adjustment layer and the exposed part of the substrate are synchronously etched by the second etching to obtain a pyramid structure on the substrate. In this way, the length of the bottom edge of the pyramid structure is conveniently and accurately controlled by means of the opening pattern; and the formation height of the pyramid structure is conveniently and accurately controlled by means of the thickness setting of the second adjustment layer, so that the etching of the substrate is stopped synchronously when the etching of the second adjustment layer is completed. In this way, the present application effectively improves the control precision of the pyramid structure morphology parameters, reduces the reflectivity of the obtained pyramid structure to incident light, and further ensures and improves the conversion efficiency of the photovoltaic cell. Moreover, the process difficulty is effectively simplified and the preparation cost is reduced.

[0085] Please refer to S10 in Figure 1 and Figure 5 In step S10, a substrate 10 is provided, which has opposite two sides. The present application does not make special limitation on the type of the substrate 10, for example, the substrate 10 can include a single crystal silicon substrate, a polycrystalline silicon substrate, a silicon epitaxial substrate, etc.

[0086] The present application also does not make special limitation on the shape, size and thickness of the substrate 10, which can be selected according to actual needs.

[0087] Please refer to S20 in Figure 1 and Figure 6 In step S20, a first adjustment layer 20 is formed on at least one side of the substrate 10; the first adjustment layer 20 and the substrate 10 have different etching selectivities.

[0088] Here, the first adjustment layer 20 and the substrate 10 can be set to have different acid and alkali corrosion selectivities. For example, the first adjustment layer 20 is set to be resistant to acid but not to alkali, and the substrate 10 is set to be resistant to alkali but not to acid; or the first adjustment layer 20 can also be set to be resistant to alkali but not to acid, and the substrate 10 is set to be resistant to acid but not to alkali. The present application does not make limitation on the specific acid and alkali corrosion selectivities of the first adjustment layer 20 and the substrate 10.

[0089] In one specific embodiment, the first regulating layer 20 includes SiO2. x Layer, SiN y The first regulating layer 20 can be prepared using at least one of the above-mentioned materials, such as a SiO2 layer, a PSG layer, and a BSG layer, wherein both x and y are positive numbers. For example, this application may use one of the above-mentioned materials to prepare the first regulating layer 20, or it may use two or more of the above-mentioned materials to prepare the first regulating layer 20. x Including at least one of silicon dioxide (SiO2) and silicon tetroxide (Si3O4); SiN y Including silicon nitride (Si3N4).

[0090] This application does not limit the method of preparing the first conditioning layer 20; any method can be selected according to the actual situation. For example, physical vapor deposition (PVD) or chemical vapor deposition (CVD) can be used to prepare the first conditioning layer 20. By using the above-mentioned material as the first conditioning layer 20, this application can enable it to act as a "mask" in subsequent etching processes.

[0091] Please see Figure 1 S30 and Figure 7 In step S30, a second adjustment layer 30 with a preset thickness value is formed on the side of the first adjustment layer 20 away from the substrate 10; the second adjustment layer 30 has the same etching selectivity as the substrate 10; and the second adjustment layer 30 has a plurality of through holes H1 penetrating itself in its thickness direction; the through holes H1 are used to define the number of pyramid structures formed.

[0092] Here, the obtained vias H1 are used in subsequent steps to pattern the relevant film layers through vias H1 to prepare the pyramid structure. Therefore, based on the adjustment of the formation density (i.e., porosity) of vias H1 in this step, the number of pyramid structures formed in subsequent steps can be defined.

[0093] In one specific embodiment, the step of forming the second adjustment layer 30 on the side of the first adjustment layer 20 facing away from the substrate 10 includes:

[0094] Oxygen atoms are doped into silicon-based thin films during deposition processes to obtain oxygen-containing crystalline silicon films with multiple through-holes H1; the oxygen-containing crystalline silicon film serves as a second conditioning layer; the porosity of the oxygen-containing crystalline silicon film ranges from 60% to 97%; the average diameter of the through-holes H1 ranges from 2 nm to 1000 nm.

[0095] This application does not impose any special limitations on the deposition process, as long as it can be used to form an oxygen-containing crystalline silicon film. For example, chemical vapor deposition, physical vapor deposition, and other methods can be used to prepare an oxygen-containing crystalline silicon film.

[0096] The inventors have found that the silicon-based thin film obtained by using the deposition process has a pinhole characteristic, and by adjusting the relevant process parameters, the formation density (i.e. porosity) of the pinholes can be controlled. Furthermore, by incorporating oxygen atoms while depositing the silicon-based thin film using the deposition process, the average diameter of the pores in the oxygen-containing crystalline silicon film can be further controlled to ensure that the relevant etching solution can pass through the pores. In this way, the present application uses the aforementioned oxygen-containing crystalline silicon film as the second adjustment layer 30, and by adjusting the porosity of the second adjustment layer 30 and the average diameter of the through holes H1, the etching process in the subsequent steps can be conveniently and accurately controlled, thereby controlling the number of pyramid structures formed.

[0097] In some embodiments, the porosity of the oxygen-containing crystalline silicon film includes 60-97%, for example, the porosity of the oxygen-containing crystalline silicon film includes but is not limited to 60%, 70%, 80%, 90%, 97%, or a range formed by any two of them.

[0098] In some embodiments, the average diameter of the through holes H1 includes 2nm-1000nm, for example, the average diameter of the through holes includes but is not limited to 2nm, 10nm, 50nm, 100nm, 200nm, 400nm, 600nm, 800nm, 1000nm, or a range formed by any two of them. By further limiting the porosity of the oxygen-containing crystalline silicon film and the average diameter of the through holes H1, it is beneficial to prepare a substrate with lower reflectivity.

[0099] Please refer to Figure 1 S40 and Figure 8 In step S40, the first adjustment layer 20 is etched with the second adjustment layer 30 as a mask to remove the part of the first adjustment layer 20 exposed by the through holes H1 and form an opening pattern H2 with a preset width value; the opening pattern H2 is used to define the side length of the base of the pyramid structure.

[0100] It can be understood that based on the same etching selectivity of the second adjustment layer 30 and the substrate 10 and the different etching selectivity of the first adjustment layer 20 and the substrate 10, the second adjustment layer 30 can be used as a mask to selectively etch (e.g. first type etching) the first adjustment layer 20 to obtain an opening pattern H2 corresponding to the formation density (i.e. porosity) of the through holes H1.

[0101] Please refer to Figure 9Here, the opening width w2 of the opening pattern H2 is not the same as the opening width w1 of the through hole H1. For example, the opening width w2 of the opening pattern H2 can be conveniently and accurately controlled to a preset width value by adjusting process parameters such as the first type etching time. Then, the subsequent step can be based on the opening pattern H2 related film layer to prepare a pyramid structure by patterning etching, so that the opening width w2 of the opening pattern H2 can define the side length of the pyramid structure in the subsequent step.

[0102] Specifically, the first type etching is to soak the acid etching solution in the first type etching solution, such as Figure 7 As shown: a structure including a first adjustment layer 20 and a second adjustment layer 30. During etching, the acid etching solution can penetrate through the through hole H1 in the second adjustment layer 30 and react with the first adjustment layer 20 exposed by the through hole H1, so that the part of the first adjustment layer 20 exposed by the through hole H1 is corroded by the acid etching solution and dissolved, thereby forming an opening pattern H2 through the first adjustment layer 20, providing a position for etching in the subsequent step to form an inverted pyramid pit. And by adjusting the etching time and other process parameters, the etching continues in the direction perpendicular to the thickness of the first adjustment layer 20, ensuring that the opening width w2 of the opening pattern H2 reaches its preset width value.

[0103] Further, the thickness of the first adjustment layer 20 includes: 10nm~300nm; Correspondingly, the first type etching includes: using a solution with a mass percentage of 0.1~10wt% HF to etch the first adjustment layer 20 at a reaction temperature of 25~35℃ for 0.2min~10min.

[0104] For example, the thickness of the first adjustment layer 20 includes but is not limited to 10nm, 20nm, 100nm, 150nm, 200nm, 250nm, 300nm or a range consisting of any two of them; the temperature of the first type etching at 25~35℃ includes but is not limited to 25℃, 26℃, 29℃, 32℃, 35℃ or a range consisting of any two of them; the time of the first type etching is 0.2~10min, and the above time includes but is not limited to 0.2min, 1min, 3min, 5min, 7min, 9min, 10min or a range consisting of any two of them.

[0105] By using the above concentration range of HF for the first type etching, the first adjustment layer 20 can be selectively etched without etching the second adjustment layer 30, which is beneficial to the preparation of the substrate with pyramid structure in the subsequent step. By limiting the reaction temperature, time and thickness of the first adjustment layer of the first type etching in the above range, the pyramid structure with suitable morphology can be prepared, which is beneficial to reduce the reflectivity of the substrate.

[0106] Please refer to Figure 1 S50 and Figure 10 In step S50, the second type of etching is performed synchronously on the second adjustment layer 30 and the part of the substrate 10 exposed by the opening pattern H2 to obtain the pyramid structure G0 on the substrate 10; wherein the thickness of the second adjustment layer 30 is used to define the formation height of the pyramid structure G0.

[0107] Here, based on the same etching selectivity of the second adjustment layer 30 and the substrate 10, the second adjustment layer 30 can be used as a reference for etching the substrate 10, that is, the second type of etching is performed synchronously on the second adjustment layer 30 and the part of the substrate 10 exposed by the opening pattern H2, and the first adjustment layer 20 with different etching selectivity is used as an etching stop layer to end the second type of etching when the second adjustment layer 30 is consumed. In this way, by adjusting the thickness of the second adjustment layer 30 in step S30, the formation height of the pyramid structure G0 can be conveniently and accurately controlled.

[0108] Specifically, the second type of etching is to use a mixed solution including an alkali solution and a texturing additive to soak the structure including the first adjustment layer 20 and the second adjustment layer 30 as shown in Figure 8 . As shown in Figure 10 , during the etching process, the second adjustment layer 30 and the substrate 10 are alkali-resistant but not acid-resistant, so the mixed solution including the alkali solution and the texturing additive corrodes and removes the second adjustment layer 30, and the mixed solution also etches the substrate 10 via the opening pattern H2 to form the pyramid structure G0, while the first adjustment layer 20 with different etching selectivity is retained as a "mask", and the part under the mask is corroded by the mixed solution including the alkali solution and the texturing additive to become the platform part in the pyramid structure G0. In addition, by setting the thickness of the second adjustment layer 30 and the etching parameters of the second type of etching, the second type of etching is stopped after the second adjustment layer 30 is etched, and thus the height of the obtained pyramid structure G0 can be controlled.

[0109] In addition, the thickness of the second adjustment layer 30 includes: 5~300nm; correspondingly, the second type of etching includes: using a mixed solution with a mass percentage content including 0.1~10wt% of an alkali solution and 0.1~10wt% of a texturing additive to etch the second adjustment layer 30 and the part of the substrate 10 exposed by the opening pattern H2 for 200s~1000s at a reaction temperature of 50℃~85℃.

[0110] The alkali in the alkali solution includes at least one of sodium hydroxide, potassium hydroxide, calcium hydroxide, ammonia, sodium carbonate, and potassium carbonate. For example, the mass percentage content of the alkali solution includes but is not limited to 0.1wt%, 1wt%, 3wt%, 5wt%, 7wt%, 9wt%, 10wt%, or a range composed of any two of them.

[0111] The texturing additive includes at least one of an inhibitor, a surfactant, a buffer, a metal particle, a fluoride, a complexing agent, and a chelating agent. The inhibitor includes at least one of ethanol, isopropyl alcohol, ethylenediamine, and triethanolamine; the surfactant includes at least one of sodium dodecyl sulfate, polyethylene glycol, and polyvinyl alcohol; the buffer includes at least one of sodium carbonate and sodium phosphate; the metal particle includes at least one of tin ions and zinc ions; the fluoride includes at least one of hydrofluoric acid and sodium fluoride; the complexing agent includes at least one of citric acid and EDTA; and the chelating agent can be tartaric acid. For example, the mass percentage content of the texturing additive includes, but is not limited to, 0.1 wt%, 1 wt%, 3 wt%, 5 wt%, 7 wt%, 9 wt%, 10 wt%, or a range composed of any two of them.

[0112] For example, the thickness of the second adjustment layer 30 includes, but is not limited to, 5 nm, 10 nm, 20 nm, 100 nm, 150 nm, 200 nm, 250 nm, 300 nm, or a range composed of any two of them; the reaction temperature of the second type etching includes, but is not limited to, 50°C, 60°C, 70°C, 80°C, 85°C, or a range composed of any two of them at 50-85°C; and the reaction time of the second type etching is 200-1000 s, and the above-mentioned time includes, but is not limited to, 200 s, 300 s, 400 s, 500 s, 600 s, 700 s, 800 s, 900 s, 1000 s, or a range composed of any two of them.

[0113] The application can selectively etch the second adjustment layer without etching the first adjustment layer by using the above-mentioned mixed solution including the lye and the texturing additive for the second type etching, which is conducive to preparing a substrate including a pyramid structure. By limiting the reaction temperature, time of the second type etching, and the thickness of the second adjustment layer in the above-mentioned ranges, a pyramid structure with a suitable height can be prepared, which is conducive to reducing the reflectivity of the substrate.

[0114] The application can prepare a pyramid structure G0 with a forming width of 10-100 nm and a forming height of 2-200 nm by the above-mentioned preparation method. For example, the forming width includes, but is not limited to, 10 nm, 50 nm, 100 nm, or a range composed of any two of them; and the thickness of the second adjustment layer includes, but is not limited to, 2 nm, 10 nm, 20 nm, 100 nm, 150 nm, 200 nm, or a range composed of any two of them. The above-mentioned forming width and forming height are caused by controlling the opening width w2 of the opening pattern H2 and the thickness of the second adjustment layer 30. The pyramid structure G0 with the above-mentioned forming width and forming height can make the substrate have good light trapping efficiency.

[0115] Please refer toFigure 1 S60 and Figure 11 In step S60, the remaining first adjustment layer 20 is removed; the remaining substrate 10 and the pyramid structure G0 together constitute a substrate.

[0116] For example, a first type of etching (for example, acid etching) is performed on the structure obtained after step S50 to remove the remaining first adjustment layer 20 to sufficiently expose the pyramid structure G0.

[0117] The acid solution is not particularly limited in the present application, as long as it can remove the first adjustment layer 20. For example, a 0.1-10wt% HF solution can be used for treatment at 25-35°C for 0.2-10min. By using the above acid solution for pickling, it is beneficial to remove the residual acid etching medium layer (i.e. the first adjustment layer 20) and reduce the damage to the substrate with a pyramid structure.

[0118] In the above embodiments, the first adjustment layer 20 and the second adjustment layer 30 are used to prepare a pyramid structure on at least one side of the substrate 10, with different sensitivities to acid and base. This method does not introduce any metal particles, avoiding environmental pollution by heavy metals. Compared with the related art, which requires multiple preparation of an initial mask layer, and then preparation of a high-precision photomask to expose, develop and other operations on the initial mask layer to obtain a mask layer, and etching the substrate with the mask layer to obtain a pyramid structure, the method provided in the embodiments of the present application can prepare a substrate with a pyramid structure by using simple acid etching and alkaline etching, which is simple in steps and easy to mass-produce in industry.

[0119] In addition, in some embodiments of the present application, the formation positions of the first adjustment layer 20 and the second adjustment layer 30 are flexibly adjusted to correspondingly adjust the formation positions of the pyramid structure. For example, after the two surfaces of the substrate 10 are treated by the above preparation method, a substrate with double-sided pyramid structure can be obtained; or only one surface of the substrate 10 is treated by the above method to form a pyramid structure on the surface; or the two surfaces of the substrate 10 are treated by different process parameters respectively to obtain pyramid structures with different topographic characteristics. The following will be described in detail with reference to the accompanying drawings.

[0120] Please refer to Figure 2 In one embodiment, the first adjustment layer 20 is formed on at least one side of the substrate, comprising:

[0121] S20', forming the first adjustment layer only on one side of the substrate.

[0122] S30', forming a second adjustment layer with a preset thickness value on the side of the first adjustment layer away from the substrate; the second adjustment layer has a plurality of through holes penetrating through itself in the thickness direction.

[0123] S40', performing first-type etching on the first adjustment layer 20 to form an opening pattern H2 with a preset width value, taking the second adjustment layer 30 as a mask.

[0124] S50', performing second-type etching on the second adjustment layer 30 and the part of the substrate 10 exposed by the opening pattern H2 to obtain a pyramid structure on the substrate 10.

[0125] S60', removing the remaining first adjustment layer 20, and the remaining substrate 10 and the pyramid structure together constitute a substrate.

[0126] In the embodiment, since the first adjustment layer 20 and the second adjustment layer 30 are only prepared on one side of the substrate 10, when etching is performed using a mixed solution including an alkali solution and a texturing additive in the second-type etching, the pyramid structures formed on both sides of the substrate 10 will have different morphological characteristics, for example, the side with the first adjustment layer 20 and the second adjustment layer 30 is formed into a first-type pyramid structure (inverted pyramid); the side without the first adjustment layer 20 and the second adjustment layer 30 is formed into a second-type pyramid structure (normal pyramid), which meets the morphological requirements of different cells for the pyramid structure.

[0127] Referring to Figure 12 In step S20', the first adjustment layer 20 is only formed on one side of the substrate 10.

[0128] For example, the forming method of the first adjustment layer 20 can be performed by referring to the aforementioned step S20.

[0129] Referring to Figure 13 In step S30', the second adjustment layer 30 with a preset thickness value is formed on the side of the first adjustment layer 20 away from the substrate 10; the second adjustment layer 30 has a plurality of through holes H1 penetrating through itself in the thickness direction.

[0130] For example, the forming method of the second adjustment layer 30 can be performed by referring to the aforementioned step S30.

[0131] Referring to Figure 14 In step S40', the first-type etching is performed on the first adjustment layer 20 to form the opening pattern H2 with the preset width value, taking the second adjustment layer 30 as a mask.

[0132] For example, the forming method of the opening pattern H2 can be performed by referring to the aforementioned step S40.

[0133] Referring to Figure 15 In step S50', the second-type etching is performed on the second adjustment layer 30 and the part of the substrate 10 exposed by the opening pattern H2 to obtain the pyramid structure on the substrate 10.

[0134] For example, the second type of etching can be performed according to the aforementioned step S50. Here, based on the difference of the etching environment of the second type of etching, for example, on the side of the substrate 10 where the first adjustment layer 20 and the second adjustment layer 30 are formed, the etching solution needs to penetrate, pass through the through holes H1 and the opening patterns H2 to perform the etching on the defined area of the substrate 10; while on the side of the substrate 10 where the first adjustment layer 20 and the second adjustment layer 30 are not formed, the etching solution can perform the etching on the entire surface. In this way, the pyramid structures obtained based on the etching characteristics (for example, anisotropy) of the etching solution have different topographic features. For example, including: the first type of pyramid structure G1 (inverted pyramid) and the second type of pyramid structure G2 (normal pyramid).

[0135] Referring to Figure 16 In step S60', the remaining first adjustment layer 20 is removed, and the remaining substrate 10 and the pyramid structure together constitute a substrate.

[0136] For example, the removal step of the first adjustment layer 20 can be performed according to the aforementioned step S60.

[0137] Referring to Figure 3 In another embodiment, the first adjustment layer 20 is formed on at least one side of the substrate, including:

[0138] S20', only forming the first adjustment layer with a preset thickness value on one side of the substrate.

[0139] S30', forming a second adjustment layer with a preset thickness value on the side of the first adjustment layer away from the substrate; the second adjustment layer has a plurality of through holes penetrating through itself in the thickness direction.

[0140] S40', performing the first type of etching on the first adjustment layer with the second adjustment layer as a mask to form an opening pattern with a preset width value.

[0141] S45, forming a protective layer on the side of the substrate away from the first adjustment layer.

[0142] S50', synchronously performing the second type of etching on the second adjustment layer and the part of the substrate exposed by the opening pattern to obtain a pyramid structure on one side of the substrate.

[0143] S60'', removing the remaining first adjustment layer and the protective layer, and the remaining substrate and the pyramid structure together constitute a substrate.

[0144] In this embodiment, a substrate with only one side as a pyramid structure G0, i.e. a single-sided pyramid structure substrate, can be prepared to meet the topographic requirements of different batteries for pyramid structures.

[0145] Referring to Figures 12 to 14, sequentially performing steps S20', S30' and S40' to obtain a structure including the first adjustment layer 20, the second adjustment layer 30, the through hole H1 and the opening pattern H2.

[0146] For example, the above steps can be performed with reference to the aforementioned steps S20, S30 and S40.

[0147] Referring to Figure 17 In step S45, the protective layer 40 is formed on the side of the substrate 10 away from the first adjustment layer 20.

[0148] In one embodiment, the protective layer 40 includes at least one of a SiO x layer, a SiN y layer, a PSG layer, a BSG layer, wherein x and y are positive numbers. For example, the protective layer 40 can be prepared using one of the above materials, or can be prepared using two or more of the above materials. The SiO x includes at least one of silicon dioxide (SiO2) and silicon trioxide (Si3O4); the SiN y includes silicon nitride (Si3N4).

[0149] The application does not limit the way of preparing the protective layer 40, which can be selected according to actual conditions. For example, the protective layer 40 can be prepared using physical vapor deposition (PVD) or chemical vapor deposition (CVD). By using the above materials as the protective layer 40, the protective layer 40 can play a "protective layer" role in subsequent etching processes.

[0150] The application does not specially limit the thickness of the protective layer 40, as long as it can cover and fill the surface and pores of the second adjustment layer 30, so that the surface of the substrate 10 is not corroded by the mixed solution including the lye and the texturing additive. For example, the protective layer 40 can be set to 200-500 nm on the non-side.

[0151] Referring to Figure 18 In step S50', the second adjustment layer 30 and the portion of the substrate 10 exposed for the opening pattern H2 are subjected to a second type of etching to obtain a pyramid structure G0 on the side of the substrate 10.

[0152] For example, the step of performing the second type of etching can be performed with reference to the aforementioned step S50.

[0153] Referring to Figure 19 In step S60'', the remaining first adjustment layer 20 and the protective layer 40 are removed, and the remaining substrate 10 and the pyramid structure G0 together constitute a substrate.

[0154] For example, the removing step of the first adjustment layer 20 and the protection layer 40 can be performed with reference to the aforementioned step S60.

[0155] In the aforementioned preparation method, because the first adjustment layer 20 and the second adjustment layer 30 are sequentially arranged on one side of the substrate 10, the first-type etching only occurs on the side with the first adjustment layer 20 and the second adjustment layer 30, without affecting the other side. When the first-type etching is completed, a protection layer 40 is arranged on the other side to protect the other side from corrosion in the second-type etching, so that the other side can be used as the back surface of the photovoltaic cell to maintain a high reflectivity of the surface and realize secondary use of the incident light spectrum, thereby further improving the conversion efficiency of the photovoltaic cell.

[0156] Referring to Figure 4 In yet another embodiment, the first adjustment layer 20 is formed on at least one side of the substrate 10, including:

[0157] S20'', the first adjustment layer is formed on both sides of the substrate.

[0158] S30'', the second adjustment layer with a preset thickness value is formed on the side of each first adjustment layer 20 away from the substrate; each second adjustment layer has a plurality of through holes penetrating itself in the thickness direction.

[0159] S40'', the first-type etching is performed on the corresponding first adjustment layer with each second adjustment layer as a mask to form an opening pattern penetrating each first adjustment layer.

[0160] S50'', the second-type etching is synchronously performed on each second adjustment layer and the part of the substrate exposed by each opening pattern to obtain a pyramid structure on both sides of the substrate.

[0161] S60', the remaining first adjustment layer is removed; the remaining substrate and the pyramid structure together constitute a substrate.

[0162] In this embodiment, a substrate with a double-sided pyramid structure G0, i.e., a double-sided pyramid structure substrate, can be prepared to meet the morphological requirements of different cells for the pyramid structure.

[0163] Referring to Figure 6 In step S20'', the first adjustment layer 20 is formed on both sides of the substrate 10.

[0164] For example, this step can be performed with reference to the aforementioned step S20.

[0165] Referring to Figure 7In step S30'', the second adjustment layer 30 with a preset thickness is formed on the side of each first adjustment layer 20 away from the substrate 10; each second adjustment layer 30 has a plurality of through holes H1 in the thickness direction.

[0166] For example, this step can be performed with reference to the aforementioned step S30.

[0167] For example, this step can be performed with reference to the aforementioned step S40. Figures 8 to 9 In step S40'', the first type etching is performed on the corresponding first adjustment layer 20 with each second adjustment layer 30 as a mask, so as to form an opening pattern penetrating each first adjustment layer 20.

[0168] For example, this step can be performed with reference to the aforementioned step S40.

[0169] For example, this step can be performed with reference to the aforementioned step S50. Figure 10 For example, this step can be performed with reference to the aforementioned step S50.

[0170] For example, this step can be performed with reference to the aforementioned step S60.

[0171] Figure 11 For example, this step can be performed with reference to the aforementioned step S60, and the pyramid structure G0 obtained in this step is a first type pyramid structure (inverted pyramid structure).

[0172] For example, this step can be performed with reference to the aforementioned step S60, and the pyramid structure G0 obtained in this step is a first type pyramid structure (inverted pyramid structure).

[0173] In some embodiments, the above preparation method can be used to prepare a substrate with a double-inverted pyramid structure, so as to meet the requirements of different batteries for the morphology of the pyramid structure of the substrate.

[0174] In addition, the substrate preparation method of the present application further comprises:

[0175] Before forming the first adjustment layer, the substrate is subjected to a first type cleaning treatment; and

[0176] After obtaining the pyramid structure, the substrate is subjected to a second type cleaning treatment.

[0177] In the present application, the first type cleaning treatment is not particularly limited, for example, a NaOH or KOH solution with a mass percentage of 0.5-5wt% can be used for cleaning at 80-85℃ for 2-15min. After the cleaning treatment, the substrate can be subjected to a drying treatment.

[0178] ​The first cleaning treatment is used to clean the substrate, remove impurities on the surface of the substrate and remove damage on the surface of the substrate, so that a clean substrate is obtained, which is conducive to the deposition of the first adjustment layer 20 and the second adjustment layer 30, and further conducive to the preparation of the inverted pyramid structure.

[0179] The second cleaning treatment is not specially limited in the present application, and can be selected according to actual needs. For example, it can be a standard RCA cleaning process.

[0180] The second cleaning treatment is used to clean the substrate, remove impurities on the surface of the substrate and remove damage on the surface of the substrate, so that a clean substrate is obtained, which is conducive to the deposition of the first adjustment layer 20 and the second adjustment layer 30, and further conducive to the preparation of the inverted pyramid structure.

[0181] Please refer to Figure 20 The second aspect of the present application provides a photovoltaic cell for the practical application of the substrate preparation method provided in some embodiments. The photovoltaic cell comprises:

[0182] A substrate 10 obtained by the above substrate preparation method; the substrate 10 has two opposite sides;

[0183] A first functional layer 50 located on one side of the substrate 10; the first functional layer 50 is configured to form a PN junction with the substrate 10;

[0184] A second functional layer 60 located on the side of the substrate 10 away from the first functional layer 50; the second functional layer 60 is configured to form a back surface field of the substrate 10;

[0185] An electrode structure 70 located on the side of the first functional layer 60 and the second functional layer 70 away from the substrate 10.

[0186] For example, the first functional layer 50 comprises a first intrinsic semiconductor layer, a first doped semiconductor layer and a first transparent conductive layer stacked in sequence.

[0187] For example, the second functional layer 60 comprises a second intrinsic semiconductor layer, a second doped semiconductor layer and a second transparent conductive layer stacked in sequence.

[0188] For example, the first transparent conductive layer and / or the second transparent conductive layer comprises at least one of indium tin oxide (ITO), fluorine-doped tin oxide (FTO), aluminum zinc oxide (AZO).

[0189] For example, the first doped semiconductor layer and / or the second doped semiconductor layer comprises at least one of single crystal silicon, polycrystalline silicon, amorphous silicon, cadmium telluride, organic semiconductor material, copper indium gallium selenide, nanoporous titanium dioxide.

[0190] For example, the electrode structure 70 comprises at least one of silver (Ag), copper (Cu) and aluminum (Al).

[0191] In another embodiment, the electrode structure 70 is located on the side of the first functional layer 60 or the second functional layer 70 facing away from the substrate.

[0192] The application will be further described in detail below through specific examples.

[0193] Example 1

[0194] The method for preparing a substrate with a pyramid structure provided by the present embodiment comprises the following steps:

[0195] 1) The substrate is subjected to a first type of cleaning and drying, the reagent used for the first type of cleaning is a mixed solution of 5wt% alkali and 5wt% hydrogen peroxide, the cleaning is performed at a temperature of 70°C for a duration of 180s, and the oil stains and the like on the surface of the substrate are removed, and then the substrate is cleaned with a 5wt% alkali solution at a temperature of 83°C for 180s, and the mechanical damage layer of the substrate is removed; subsequently, RCA cleaning is performed and drying is performed; the alkali solution comprises a potassium hydroxide solution;

[0196] 2) A first adjustment layer and a second adjustment layer are respectively arranged on both sides of the substrate, the second adjustment layer has a plurality of through holes penetrating through the second adjustment layer in the thickness direction; wherein,

[0197] The first adjustment layer is a SiNx layer with a thickness of 300nm;

[0198] The second adjustment layer is a doped microcrystalline P layer with a thickness of 20nm, the maximum size of the pores of the through holes of the layer is 500nm, and the porosity is 80%.

[0199] 3) A first type of etching is performed on one side of the above-mentioned first intermediate substrate layer by using an acidic etching solution, and the first adjustment layer exposed by the above-mentioned through holes is removed;

[0200] The acidic etching solution is HF with a mass percentage of 2%;

[0201] The temperature of the first type of etching is 25°C, and the time is 2min.

[0202] 4) A second type of etching treatment is performed on both sides of the structure obtained after step 3 is performed by using a mixed solution comprising an alkali solution and a texturing additive;

[0203] The mixed solution comprising an alkali solution and a texturing additive comprises 1wt% of an alkali solution and 0.5wt% of a texturing additive, the alkali solution is potassium hydroxide, and the texturing additive is a conventional texturing additive;

[0204] The temperature of the second type of etching treatment is 80°C, and the time is 420s.

[0205] 5) The structure obtained after step 4 is performed is subjected to an acid washing treatment, and the residual first adjustment layer is removed, and a substrate with a pyramid structure is obtained.

[0206] The pickling process involved treating the sample with 5 wt% HF at 25°C for 2 minutes.

[0207] 6) Perform an RCA cleaning procedure on the substrates, including those with pyramidal structures.

[0208] The substrate with a pyramid structure prepared in this embodiment is as follows: Figure 11 As shown.

[0209] Example 2

[0210] The substrate preparation method with a pyramid structure provided in this embodiment is basically the same as that in Embodiment 1, except that the first adjustment layer and the second adjustment layer are sequentially provided only on one side of the substrate.

[0211] The subsequent preparation steps are the same as in Example 1.

[0212] Step 2) also includes providing a protective layer with a thickness of 300 nm on the other side of the substrate.

[0213] The substrate prepared in this embodiment has a pyramidal structure on one side, as shown below. Figure 19 As shown, by Figure 19 As can be seen, the substrate prepared by the method of this embodiment has a pyramid structure on one side and no pyramid structure on the other side surface.

[0214] Example 3

[0215] The substrate preparation method with a pyramid structure provided in this embodiment is basically the same as that in Embodiment 1, except that in step 2), the first adjustment layer and the second adjustment layer are not deposited on one side of the substrate, and the subsequent processing conditions are the same as those in Embodiment 1.

[0216] The subsequent preparation steps are the same as in Example 1.

[0217] The substrate of the first type pyramid structure (i.e., inverted pyramid structure) and the second type pyramid structure (i.e., upright pyramid structure) prepared in this embodiment is as follows: Figure 16 As shown.

[0218] Example 4

[0219] The substrate fabrication method with a pyramid structure provided in this embodiment is basically the same as that in Embodiment 1, except that in step 2):

[0220] The first adjustment layer is a 300nm thick BSG layer;

[0221] The second regulating layer is a 30nm thick microcrystalline N layer with a maximum pore size of 200nm and a porosity of 85%.

[0222] In step 3) :

[0223] The acidic etching solution is HF with a mass percentage of 5%;

[0224] The temperature of the first type of etching is 25°C, and the time is 3 min.

[0225] In step 4) :

[0226] The mixed solution including the lye and the texturing additive includes 1wt% of the lye and 0.5wt% of the texturing additive, the lye is potassium hydroxide, and the texturing additive is a conventional texturing additive;

[0227] The temperature of the second type of etching is 80°C, and the time is 300 s.

[0228] In step 5) :

[0229] It is treated with HF with a mass percentage of 5wt% at 30°C for 2-4 min.

[0230] Example 5

[0231] The substrate preparation method provided in the embodiment is basically the same as that in Example 1, and the difference lies in that in step 2) :

[0232] The first adjustment layer is a SiOx layer with a thickness of 200 nm;

[0233] The second adjustment layer is an intrinsic amorphous silicon layer with a thickness of 60 nm, the maximum size of the pores of the through holes of the layer is 400 nm, and the porosity is 65%.

[0234] In step 3) :

[0235] The acidic etching solution is HF with a mass percentage of 3%;

[0236] The temperature of the first type of etching is 30°C, and the time is 1 min.

[0237] In step 4) :

[0238] The mixed solution including the lye and the texturing additive includes 1wt% of the lye and 1wt% of the texturing additive, the lye is potassium hydroxide, and the texturing additive is a conventional texturing additive;

[0239] The temperature of the second type of etching is 85°C, and the time is 500 s.

[0240] In step 5) :

[0241] It is treated with HF with a mass percentage of 5wt% at 30°C for 4 min.

[0242] Example 6

[0243] The preparation method of the substrate with the pyramid structure provided in this embodiment is basically the same as that in Embodiment 1, except that the maximum size of the pores of the second adjustment layer via hole is 500 nm and the porosity is 90% in this embodiment.

[0244] Comparative Example 1

[0245] This comparative example is to use the substrate with the pyramid structure prepared in the invention patent CN107611226B. The preparation method includes the following steps:

[0246] 1) providing a substrate, and performing metal-assisted chemical etching on the substrate to form a napping point.

[0247] The metal-assisted chemical etching specifically includes the following steps:

[0248] HF / HNO3 / DIW (deionized water) solution is used for cleaning, the solution ratio is 1:4-6:1-6, the cleaning temperature is 0°C-8°C, the cleaning time is 10s-120s, deionized water is used for cleaning at room temperature for 60s-180s, metal-assisted chemical etching is performed using HF / H2O2 / DIW / additive, wherein the additive can be nitrate of Ag, Cu, Au and the like, the solution ratio is 1:1-7:1-7 (additive 100-1000mL), the etching temperature is 15°C-65°C, the etching time is 20s-240s, then deionized water is used for cleaning again for 60s-180s, HNO3 with a concentration of 69% is used for etching at room temperature for 60s-180s to sufficiently remove metal ions, deionized water is used for cleaning at room temperature for 60s-180s, HF with a concentration of 1%-20% is used for etching at room temperature for 60s-180s, deionized water is used for cleaning at room temperature for 60s-180s, KOH with a concentration of 0.1%-10% is used for etching at room temperature for 60s-180s, deionized water is used for cleaning at room temperature for 60s-180s, HCL / H2O2 / DIW is used for etching, wherein the solution ratio is 1:1-10:1-10, the etching temperature is 25°C-75°C, the etching time is 60s-180s, deionized water is used for cleaning at room temperature for 60s-180s, HF / HCl / DIW is used for etching, wherein the solution ratio is 1:1-10:1-10, the etching temperature is room temperature, the etching time is 60s-180s, deionized water is used for cleaning at room temperature for 60s-180s, then hot water with a temperature of 60°C-90°C is used for cleaning, and then drying for 300s-600s.

[0249] 2) dry ion etching is performed on the substrate after the metal-assisted chemical etching to obtain an inverted pyramid structure.

[0250] The dry ion etching comprises the following steps: the etching time is 120s-300s; the reaction chamber pressure is 24Pa-100Pa; the chlorine gas flow is 400sccm-4000sccm; the oxygen gas flow is 1000sccm-3000sccm; the SF6 gas flow is 700sccm-3000sccm; the chlorine gas flow is 700sccm-4000sccm; the oxygen gas flow is 1800sccm-5000sccm; the SF6 gas flow is 650sccm-4000sccm; the radio frequency power is 24000W-100000W to carry out the reactive ion etching to obtain the inverted pyramid structure.

[0251] 3) The RCA cleaning process is carried out on the substrate after the dry ion etching.

[0252] Test example

[0253] The surface reflectivity of the substrates with the pyramid structure prepared in examples 1-6 and comparative example 1 is measured by the reflectivity testing equipment, and the results are shown in Table 1.

[0254] Table 1-reflectivity measurement results

[0255] Reflectance on one side / % Reflectance on the other side / % Example 1 3.87% 3.87% Example 2 3.87% 35.77% Example 3 3.87% 10.62% Example 4 4.5% 4.5% Example 5 4.5% 4.5% Example 6 3.03% 3.03% Comparative Example 1 3％～8％ 3％～8％

[0256] According to Table 1, the surface reflectivity of the substrate with the pyramid structure prepared by the metal-assisted chemical etching process in comparative example 1 is 3-8%. And based on the process characteristics, metal particle impurities are introduced, which inevitably causes environmental pollution. In addition, in the preparation process, the gas flow, radio frequency power, etching liquid concentration, component ratio and other process parameters need to be accurately adjusted, which significantly increases the preparation difficulty.

[0257] However, in examples 1-6 of the present application, the substrate with the pyramid structure is prepared by a relatively simple process, and the reflectivity is only 3-5.12%, which has good light trapping performance. In addition, compared with the method provided in comparative example 1, examples 1-6 do not introduce metal particle impurities, which is more friendly to the environment.

[0258] Finally, it should be pointed out that: the above examples are only used to illustrate the technical solutions of the present application, but not to limit them; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing examples, or make equivalent replacement for part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A substrate manufacturing method for manufacturing a substrate including a pyramid structure; characterized by, The method comprises the following steps: providing a substrate having opposite two sides; forming a first adjustment layer on at least one side of the substrate; the first adjustment layer and the substrate have different etching selectivity; forming a second adjustment layer with a preset thickness on the side of the first adjustment layer away from the substrate; the second adjustment layer and the substrate have the same etching selectivity; and the second adjustment layer has a plurality of through holes penetrating through itself in the thickness direction; the through holes are used to define the number of pyramid structures formed; performing a first type of etching on the first adjustment layer with the second adjustment layer as a mask, removing the first adjustment layer exposed by the through holes and forming an opening pattern with a preset width; the opening pattern is used to define the side length of the base of the pyramid structure; synchronously performing a second type of etching on the second adjustment layer and the substrate exposed by the opening pattern to obtain a pyramid structure on the substrate; wherein the thickness of the second adjustment layer is used to define the formation height of the pyramid structure; specifically, by setting the thickness of the second adjustment layer, the etching of the substrate is stopped synchronously when the etching of the second adjustment layer is completed, so as to realize the regulation of the formation height of the pyramid structure; remove the remaining first adjustment layer; the remaining substrate and the pyramid structure together constitute the substrate.

2. The substrate preparation method according to claim 1, wherein the step of forming a second adjustment layer on the side of the first adjustment layer away from the substrate comprises: forming a silicon-based thin film by deposition process while incorporating oxygen atoms to obtain an oxygen-containing crystalline silicon film with a plurality of through holes; the oxygen-containing crystalline silicon film as the second adjustment layer; wherein the porosity of the oxygen-containing crystalline silicon film comprises 60-97%; and the average diameter of the through holes comprises 2nm-1000nm.

3. The substrate preparation method according to claim 1, wherein the first adjustment layer comprises a SiOx layer, a SiNy layer, a PSG layer or a BSG layer, wherein x and y are positive numbers; the second adjustment layer comprises an N-type doped oxygen-containing microcrystalline layer, a P-type doped oxygen-containing microcrystalline layer or an oxygen-containing polycrystalline silicon layer.

4. The substrate preparation method according to claim 1, wherein the first type of etching comprises etching the first adjustment layer with a HF solution with a mass percentage content of 0.1-10wt% at a reaction temperature of 25-35℃ for 0.2-10min.

5. The substrate preparation method according to claim 1, wherein the second type of etching comprises synchronously etching the second adjustment layer and the substrate exposed by the opening pattern with a mixed solution of an alkali solution with a mass percentage content of 0.1wt%-10wt% and a texturing additive with a mass percentage content of 0.1wt%-10wt% at a reaction temperature of 50-85℃ for 200s-1000s.

6. The substrate preparation method according to any one of claims 1-5, wherein the thickness of the first adjustment layer comprises 10-300nm. ​ ​ ​ ​ ​ The thickness of the second adjustment layer comprises 5nm-300nm; The bottom side length of the pyramid structure comprises 10nm-100nm; The forming height of the pyramid structure comprises 2nm-200nm.

7. The substrate preparation method according to any one of claims 1-5, wherein, forming a first adjustment layer on at least one side of the substrate comprises: forming a first adjustment layer on only one side of the substrate; correspondingly, the method comprises: forming a second adjustment layer with a preset thickness value on the side of the first adjustment layer away from the substrate; the second adjustment layer has a plurality of through holes in the thickness direction; performing a first type of etching on the first adjustment layer with the second adjustment layer as a mask to form an opening pattern with a preset width value; synchronously performing a second type of etching on the second adjustment layer and the part of the substrate exposed to the opening pattern to obtain a pyramid structure on the substrate; removing the remaining first adjustment layer; the remaining substrate and the pyramid structure together constitute the substrate.

8. The substrate preparation method according to any one of claims 1-5, wherein, forming a first adjustment layer on at least one side of the substrate comprises: forming a first adjustment layer on only one side of the substrate; correspondingly, the method comprises: forming a second adjustment layer with a preset thickness value on the side of the first adjustment layer away from the substrate; the second adjustment layer has a plurality of through holes in the thickness direction; performing a first type of etching on the first adjustment layer with the second adjustment layer as a mask to form an opening pattern with a preset width value; forming a protective layer on the side of the substrate away from the first adjustment layer; synchronously performing a second type of etching on the second adjustment layer and the part of the substrate exposed to the opening pattern to obtain a pyramid structure on the side of the substrate; removing the remaining first adjustment layer and the protective layer; the remaining substrate and the pyramid structure together constitute the substrate.

9. The substrate preparation method according to any one of claims 1-5, wherein, forming a first adjustment layer on at least one side of the substrate comprises: forming a first adjustment layer on both sides of the substrate; correspondingly, the method comprises: forming a second adjustment layer with a preset thickness value on the side of each first adjustment layer away from the substrate; each second adjustment layer has a plurality of through holes in the thickness direction; performing a first type of etching on the corresponding first adjustment layer with the corresponding second adjustment layer as a mask to form an opening pattern penetrating the first adjustment layer; synchronously performing a second type of etching on each second adjustment layer and the part of the substrate exposed to each opening pattern to obtain a pyramid structure on both sides of the substrate; removing the remaining first adjustment layer; the remaining substrate and the pyramid structure together constitute the substrate.

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