Silicon wafer cleaning method, silicon wafer, heterojunction battery and electric equipment

Abstract

The invention provides a silicon wafer cleaning method, a silicon wafer, a heterojunction battery and electric equipment. The silicon wafer cleaning method comprises the following steps: sequentially carrying out the following treatments on a silicon wafer: carrying out primary saponification treatment by adopting a primary saponification treatment solution, carrying out secondary saponification treatment by adopting a secondary saponification treatment solution, carrying out oxidation treatment and carrying out passivation treatment to obtain a cleaned silicon wafer, the primary saponification treatment liquid comprises hydrogen peroxide; the secondary saponification treatment liquid comprises hydrogen peroxide; the mass percentage content of hydrogen peroxide in the primary saponification treatment liquid is greater than that of hydrogen peroxide in the secondary saponification treatment liquid. According to the method, the silicon wafer with a clean surface can be prepared, and the preparation of a heterojunction cell with high photoelectric conversion efficiency is facilitated.

Description

Technical Field

[0001] The present invention relates to the field of crystalline silicon processing, and in particular to a silicon wafer cleaning method, a silicon wafer, a heterojunction battery, and an electrical device. Background Art

[0002] Heterojunction cells have shown great potential in the photovoltaic field due to their high efficiency, low temperature coefficient, bifacial power generation capability, and low light-induced degradation. These cells achieve high photoelectric conversion efficiency by combining N-type monocrystalline silicon wafers and amorphous silicon thin films, and show better performance stability in high-temperature environments. In addition, low-temperature processing and simplified production processes also make heterojunction cells more energy-efficient and economical in the manufacturing process. However, despite their many advantages, heterojunction cells still face some challenges, especially the problem of silicon wafer quality. In the preparation process of high-efficiency heterojunction cells, in order to achieve high photoelectric conversion efficiency, silicon wafers with clean surfaces are necessary.

[0003] Dense pitting on silicon wafers can significantly impact the performance of heterojunction cells. These pitting, often caused by impurities, defects, or improper processing during wafer fabrication, can lead to surface unevenness in the cell, impacting its electrical performance. Specifically, dense pitting creates localized areas of high resistance, making it difficult for current to efficiently flow through these areas, thereby reducing the cell's overall current density and conversion efficiency. Furthermore, these pitting increases the cell's surface recombination rate, further reducing carrier lifetime and leading to a decrease in photoelectric conversion efficiency.

[0004] Therefore, solving the problem of dense pitting on silicon wafers is crucial to improving the performance of heterojunction batteries. Summary of the Invention

[0005] The present invention provides a silicon wafer cleaning method, which can solve the problem of dense pitting on silicon wafers and obtain silicon wafers with relatively clean surfaces, which is beneficial to improving the efficiency of heterojunction batteries.

[0006] The present invention also provides a silicon wafer produced by the above-mentioned cleaning method, which has high surface cleanliness and can improve the photoelectric conversion efficiency of the heterojunction battery.

[0007] The present invention also provides a heterojunction battery, comprising the silicon wafer as described above. The heterojunction battery has high photoelectric conversion efficiency and provides continuous and stable power output, which is beneficial to the stability of the battery in long-term operation.

[0008] The present invention also provides an electrical device comprising the heterojunction battery as described above. The electrical device operates relatively stably and has high overall efficiency.

[0009] In a first aspect, the present invention provides a silicon wafer cleaning method, comprising the following steps: sequentially subjecting a silicon wafer to the following treatments: a primary saponification treatment using a primary saponification treatment solution, a secondary saponification treatment using a secondary saponification treatment solution, an oxidation treatment, and a passivation treatment to obtain a cleaned silicon wafer;

[0010] The primary saponification treatment liquid includes hydrogen peroxide;

[0011] The secondary saponification treatment solution includes hydrogen peroxide;

[0012] The mass percentage of hydrogen peroxide in the primary saponification treatment liquid is greater than the mass percentage of hydrogen peroxide in the secondary saponification treatment liquid.

[0013] In the silicon wafer cleaning method described above, the ratio of the mass percentage of hydrogen peroxide in the primary saponification treatment solution to the mass percentage of hydrogen peroxide in the secondary saponification treatment solution is (1.4-1.9):1; and / or,

[0014] The mass percentage of hydrogen peroxide in the primary saponification treatment liquid is 15.5wt% to 21wt%; and / or,

[0015] The mass percentage of hydrogen peroxide in the secondary saponification treatment liquid is 8.3wt% to 15wt%; and / or,

[0016] The primary saponification treatment liquid further comprises alkali, and the mass percentage of alkali in the primary saponification treatment liquid is 0.3wt% to 0.9wt%; and / or,

[0017] The secondary saponification treatment liquid further comprises alkali, and the mass percentage of the alkali in the secondary saponification treatment liquid is 0.2 wt % to 0.7 wt %.

[0018] The silicon wafer cleaning method as described above,

[0019] The silicon wafer cleaning method further comprises: performing a degumming treatment and at least one first water washing treatment on the silicon wafer in sequence, and then performing the saponification treatment; and / or,

[0020] After the primary saponification treatment, the silicon wafer is subjected to at least one second water washing treatment, and then subjected to the secondary saponification treatment; and / or,

[0021] After the secondary saponification treatment, the silicon wafer is subjected to at least one third water washing treatment, and then subjected to the oxidation treatment; and / or,

[0022] After the oxidation treatment, the silicon wafer is subjected to at least one fourth water washing treatment, and then the passivation treatment is performed; and / or,

[0023] The silicon wafer cleaning method further includes: after the passivation treatment, performing a texturing treatment on the silicon wafer to obtain the cleaned silicon wafer.

[0024] The silicon wafer cleaning method as described above,

[0025] After the passivation treatment, the silicon wafer is subjected to texturing treatment to obtain the cleaned silicon wafer, which specifically includes: after the passivation treatment, the silicon wafer is subjected to slow pulling treatment and drying treatment in sequence, and then subjected to texturing treatment to obtain the cleaned silicon wafer.

[0026] In the silicon wafer cleaning method described above, the oxidation treatment process includes:

[0027] Providing N portions of hydrochloric acid solution, where N is an integer greater than or equal to 2;

[0028] placing the silicon wafer after the secondary saponification treatment in one portion of the hydrochloric acid solution to obtain a hydrochloric acid solution containing the silicon wafer, and adding the remaining portions of the hydrochloric acid solution to the hydrochloric acid solution containing the silicon wafer in batches at intervals of 100s to 200s;

[0029] Wherein, during the oxidation treatment, ozone is introduced into the hydrochloric acid solution containing the silicon wafer, and the oxidation treatment is performed in the presence of the ozone;

[0030] N=W1 / W2, W1 is the percentage of the total mass of the hydrochloric acid in the N parts of hydrochloric acid solution to the total mass of the oxidizing liquid used in the oxidation treatment, W2 is the percentage of the mass of the hydrochloric acid in one part of the hydrochloric acid solution in the oxidation treatment to the total mass of the oxidizing liquid used in the oxidation treatment, 0.16wt%≤W1≤0.21wt%, 0.0133wt%≤W2≤0.0175wt%; and / or,

[0031] The concentration of ozone in the oxidation treatment liquid is 50ppm to 60ppm.

[0032] The silicon wafer cleaning method as described above uses a passivation treatment solution for the passivation treatment, wherein the passivation treatment solution includes hydrofluoric acid, a water absorption-proof passivation additive, and water;

[0033] The mass percentage of the hydrofluoric acid and the anti-water absorption passivation additive in the passivation treatment solution is (3.3-9.6): (2.2-6.4).

[0034] The silicon wafer cleaning method as described above, wherein the anti-water absorption passivation additive includes a chelating agent, a surfactant, a penetrant, and an acidity regulator;

[0035] The chelating agent is aminocarboxylic acid, and the mass percentage of the chelating agent in the passivation treatment solution is 0.8wt% to 1.7wt%; and / or,

[0036] The surfactant comprises at least one of isomeric alcohol polyoxyethylene ether and glutaric acid, and the mass percentage of the surfactant in the passivation treatment solution is 0.5wt% to 1.6wt%; and / or,

[0037] The penetrant includes at least one of fatty alcohol polyoxyethylene ether and long-chain alkyl chlorosilane, and the mass percentage of the penetrant in the passivation treatment solution is 0.4-1.1wt%; and / or,

[0038] The acidity regulator comprises at least one of acetic acid and citric acid, and the mass percentage of the acidity regulator in the passivation treatment solution is 0.5wt% to 2wt%; and / or,

[0039] The treatment temperature of the primary saponification treatment is 55° C. to 70° C., and the treatment time is 200s to 350s; and / or,

[0040] The treatment temperature of the secondary saponification treatment is 55° C. to 70° C., and the treatment time is 200s to 280s; and / or,

[0041] The oxidation treatment temperature is 23° C. to 26° C., and the treatment time is 170s to 280s; and / or,

[0042] The passivation treatment has a treatment temperature of 23° C. to 26° C. and a treatment time of 180s to 290s; and / or,

[0043] The drying process has a treatment temperature of 65° C. to 85° C. and a treatment time of 600s to 1000s.

[0044] A second aspect of the present invention provides a silicon wafer, which is obtained by processing the silicon wafer cleaning method as described above.

[0045] A third aspect of the present invention provides a heterojunction battery, comprising:

[0046] A silicon wafer obtained by the silicon wafer cleaning method described above or a silicon wafer described above is used as a substrate; the substrate has two opposite sides;

[0047] A 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;

[0048] a second functional layer located on a side of the substrate facing away from the first functional layer; the second functional layer is configured to: constitute a back surface field of the substrate;

[0049] The electrode structure is located on a side of the first functional layer and / or the second functional layer facing away from the substrate.

[0050] A fourth aspect of the present invention provides an electrical device comprising the heterojunction battery described above. The silicon wafer cleaning method provided herein addresses the problem of dense pitting on silicon wafers by using high-concentration hydrogen peroxide and low-concentration hydrogen peroxide to clean the silicon wafers and adding a water-absorption-resistant passivation additive during the passivation treatment. This method produces clean silicon wafers, which is beneficial for further improving the performance of heterojunction batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0052] Figure 1 This is a schematic diagram of the process flow of the silicon wafer cleaning method provided by the present invention.

[0053] The above drawings illustrate specific embodiments of the present invention, which will be described in more detail below. These drawings and the accompanying description are not intended to limit the scope of the present invention in any way, but rather to illustrate the concept of the present invention to those skilled in the art by reference to specific embodiments. DETAILED DESCRIPTION

[0054] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0055] The cleanliness of the silicon wafer surface significantly impacts the overall current density and conversion efficiency of heterojunction cells. Currently, silicon wafers are processed using multi-wire saws, which use steel wires to drive silicon carbide abrasives to cut the wafers. This can cause organic and metal ion contamination on the wafer surface. These impurities, particularly metal particle contaminants such as Cu, Fe, and Na, can easily diffuse from the wafer surface into the interior, forming deep-level recombination centers. This can affect the non-equilibrium minority carrier lifetime and reduce the photovoltaic conversion efficiency.

[0056] If these organic pollutants are not completely removed, the problem of dense pitting on the silicon wafer will occur. These pits will increase the surface roughness of the silicon wafer and destroy the continuity and integrity of the surface passivation layer, resulting in increased light scattering and reflection, reduced effective light absorption, thereby reducing the short-circuit current and causing a significant decrease in the photoelectric conversion efficiency of the heterojunction battery.

[0057] Currently, research has used a combination of hydrogen peroxide and alkaline solution to clean silicon wafers, and hydrofluoric acid to improve their hydrophobicity. However, these methods have limited efficiency in removing contaminants from silicon wafers, and the interface differences between hydrofluoric acid and silicon wafers limit their effectiveness in improving the hydrophobicity of silicon wafers. Even after using these methods to treat silicon wafers, it is still difficult to completely resolve the problem of dense pitting defects on silicon wafers.

[0058] Therefore, how to clean silicon wafers more thoroughly is the key to completely solving the problem of dense pitting on silicon wafers and improving the efficiency of heterojunction batteries.

[0059] Based on this, the first aspect of the present invention provides a silicon wafer cleaning method, comprising the following steps: sequentially performing the following treatments on the silicon wafer: a primary saponification treatment using a primary saponification treatment solution, a secondary saponification treatment using a secondary saponification treatment solution, an oxidation treatment, and a passivation treatment to obtain a cleaned silicon wafer;

[0060] The primary saponification treatment solution includes hydrogen peroxide;

[0061] The secondary saponification treatment solution includes hydrogen peroxide;

[0062] The mass percentage of hydrogen peroxide in the first saponification treatment liquid is greater than the mass percentage of hydrogen peroxide in the second saponification treatment liquid.

[0063] In the primary saponification treatment of the present invention, a large amount of organic impurities on the surface of the silicon wafer undergo a saponification reaction in the presence of hydrogen peroxide, generating substances with good water solubility, which can be dissolved in water and removed.

[0064] Then, the secondary saponification treatment is performed again using a secondary saponification treatment solution including hydrogen peroxide to further treat the organic impurities remaining on the surface of the silicon wafer. At this time, the surface of the silicon wafer is already relatively clean.

[0065] Through oxidation treatment, the clean surface of the silicon wafer can be polished to obtain a silicon wafer with a relatively smooth surface. At the same time, the inorganic pollutants including metal particles remaining on the surface of the silicon wafer can be washed away to avoid the impact of these inorganic pollutants on the cleanliness of the silicon wafer surface. The silicon dioxide layer generated after oxidation treatment can be used as a protective layer for the silicon wafer to prevent the silicon wafer surface from being contaminated or damaged in subsequent processes.

[0066] Finally, the present invention cleans the oxide layer on the surface of the silicon wafer through passivation treatment, and significantly improves the hydrophobicity of the silicon wafer surface, thereby obtaining a clean silicon wafer with a clean surface.

[0067] It should be clarified that the mass percentage of hydrogen peroxide in the primary saponification solution of the present invention is greater than the mass percentage of hydrogen peroxide in the secondary saponification solution. Specifically, a primary saponification treatment is first performed using a primary saponification solution containing a high concentration of hydrogen peroxide, followed by a secondary saponification treatment using a secondary saponification solution containing a low concentration of hydrogen peroxide. The inventors have discovered that high concentrations of hydrogen peroxide can decompose complex organic macromolecules, making them more soluble in water and facilitating subsequent rinsing and removal. Therefore, to thoroughly remove organic contaminants from the surface of silicon wafers, a higher concentration of hydrogen peroxide is required to accelerate the oxidation and decomposition of the organic matter, thereby improving the efficiency of the entire saponification reaction. Furthermore, after a primary saponification treatment using a primary saponification solution containing a high concentration of hydrogen peroxide, a secondary saponification treatment can achieve a thorough cleaning effect using only a small amount of hydrogen peroxide. This saves reagents and improves industrial economics compared to methods using two cleaning treatments containing high concentrations of hydrogen peroxide.

[0068] The present invention uses a primary saponification treatment solution to perform a primary saponification treatment, uses a secondary saponification treatment solution to perform a secondary saponification treatment, an oxidation treatment, and a passivation treatment to clean the silicon wafer, and controls the mass percentage of hydrogen peroxide in the primary saponification treatment solution to be greater than the mass percentage of hydrogen peroxide in the secondary saponification treatment solution. Silicon wafers with a high surface cleanliness can be obtained, which is conducive to the preparation of heterojunction batteries with high efficiency.

[0069] As described above, the ratio of the mass percentage of hydrogen peroxide in the primary saponification solution to the mass percentage of hydrogen peroxide in the secondary saponification solution of the present invention is (1.4-1.9):1. For example, the ratio of the mass percentage of hydrogen peroxide in the primary saponification solution to the mass percentage of hydrogen peroxide in the secondary saponification solution includes, but is not limited to, 1.4:1, 1.5:1, 1.6:1, 1.7:1, 1.8:1, 1.9:1, or any combination thereof. By limiting the above ratio, both the thorough cleaning of organic contaminants on the silicon wafer surface and industrial cost savings are facilitated.

[0070] In another specific embodiment, the mass percentage of hydrogen peroxide in the primary saponification treatment solution is 15.5 wt % to 21 wt %. When the primary saponification treatment solution including the above hydrogen peroxide concentration is used to clean the silicon wafer, a large amount of organic pollutants on the surface of the silicon wafer can be better removed.

[0071] In another specific embodiment, the mass percentage of hydrogen peroxide in the secondary saponification treatment solution is 8.3 wt % to 15 wt %. When the secondary saponification treatment solution containing the above hydrogen peroxide concentration is used to clean the silicon wafer, a small amount of residual organic pollutants on the surface of the silicon wafer can be better removed.

[0072] In another embodiment, the primary saponification solution further comprises an alkali, wherein the alkali content in the primary saponification solution is 0.3 wt% to 0.9 wt%. The addition of the alkali to the primary saponification solution further improves the efficiency of the primary saponification process and can synergize with hydrogen peroxide to more efficiently remove organic pollutants.

[0073] In another embodiment, the secondary saponification solution further comprises an alkali, and the alkali content in the secondary saponification solution is 0.2 wt % to 0.7 wt %. The addition of the alkali to the secondary saponification solution is more conducive to further and thoroughly removing organic contaminants on the surface of the silicon wafer in synergistically with the hydrogen peroxide.

[0074] The inventors speculate that the addition of alkali may improve the efficiency of both the primary and secondary saponification processes because the decomposition of hydrogen peroxide produces highly oxidizing free radicals, such as hydroxyl radicals (OH). Hydrogen peroxide has an oxidation potential of 1.8 V, which is not very oxidizing. Adding alkali allows the alkali to decompose in the hydrogen peroxide system to produce OH radicals, raising the oxidation potential to 2.8 V. This gives the system a stronger oxidizing ability, enabling better decomposition of organic contaminants on the silicon wafer surface, resulting in cleaner silicon wafers. Furthermore, the addition of hydrogen peroxide and a small amount of alkali allows for a more effective initial polishing of the silicon wafer surface. During this process, hydrogen peroxide first oxidizes uneven surfaces on the silicon wafer, generating silicon dioxide. The silicon dioxide then reacts with the alkali to form silicates, removing these uneven surfaces and improving the reflectivity of the silicon wafer surface.

[0075] The present invention does not impose any particular limitation on the type of base, and the base may be selected according to actual needs. For example, the base may be at least one of sodium hydroxide, potassium hydroxide, and calcium hydroxide.

[0076] In addition, the above silicon wafer cleaning method further includes: performing a degumming treatment and at least one first water washing treatment on the silicon wafer in sequence, and then performing a saponification treatment.

[0077] The present invention does not impose any particular restrictions on the debonding process, as long as it can remove residual adhesive from the silicon wafer. For example, the debonding process can be performed using a debonding agent to clean the silicon wafer. The debonding agent includes polyether, surfactant, complexing agent, alkali, etc. The debonding process can initially decompose and remove organic matter such as residual adhesive from the adhesive wafer.

[0078] After the degumming treatment, the method further includes performing at least one first water washing treatment and then a saponification treatment on the degumming silicon wafer to remove the degumming agent remaining on the surface of the silicon wafer after the degumming treatment.

[0079] In order to improve the efficiency of silicon wafer cleaning, the above silicon wafer cleaning method further includes performing at least one second water washing treatment on the silicon wafer after the first saponification treatment, and then performing a second saponification treatment.

[0080] In another embodiment, after the secondary saponification treatment, the silicon wafer is subjected to at least one third water washing treatment and then subjected to oxidation treatment.

[0081] In another specific embodiment, after the oxidation treatment, the silicon wafer is subjected to at least one fourth water washing treatment and then to a passivation treatment.

[0082] The present invention provides at least one third water washing treatment between the secondary saponification treatment and the oxidation treatment, and provides at least one fourth water washing treatment between the oxidation treatment and the passivation treatment. On the one hand, it can reduce the influence of the secondary saponification treatment liquid remaining on the surface of the silicon wafer on the oxidation treatment, and on the other hand, it can also improve the efficiency of silicon wafer cleaning.

[0083] The present invention does not impose any particular restrictions on the treatment temperature, treatment method, or treatment time for the first, second, third, and fourth water washing processes, as long as the residual reagents on the silicon wafer surface can be removed. For example, the silicon wafer can be ultrasonically washed with deionized water at a temperature of 20°C to 30°C, with an ultrasonic current of 4A to 6A to ensure ultrasonic cavitation. The ultrasonic treatment time can be 150s to 250s to achieve optimal cleaning results.

[0084] In another specific embodiment, the silicon wafer cleaning method further includes: performing texturing treatment on the silicon wafer after the passivation treatment to obtain a cleaned silicon wafer.

[0085] As mentioned above, after the passivation treatment, the silicon wafer is subjected to a texturing treatment to obtain a cleaned silicon wafer, specifically: after the passivation treatment, the silicon wafer is subjected to a slow pulling treatment and a drying treatment in sequence, and then subjected to a texturing treatment to obtain a cleaned silicon wafer. Among them, the present invention does not specifically limit the slow pulling treatment and the drying treatment, as long as a dry and clean silicon wafer can be obtained. For example, the slow pulling treatment can be performed at a temperature of 23°C to 26°C, first bubbling and cleaning for 130s to 140s, and then slowly pulling and lifting. By slowly lifting the flower basket from the water, the amount of liquid adsorbed on the surface of the cell is reduced, and the cleaned cell is slowly dehydrated. The above-mentioned slow pulling operation can make the silicon wafer clean and will not leave water marks. The drying treatment is to put the silicon wafer after the slow pulling treatment into a drying tank for drying, and use the drying and drainage properties of nitrogen for drying. The drying temperature is set to 65°C to 85°C, which can further improve the drying efficiency, reduce liquid residue, and reduce the defective ratio after texturing. In addition, after the slow pulling and drying processes, the silicon wafer is also subjected to texturing. By texturing the silicon wafer, the reflectivity of the silicon wafer surface can be better reduced, and the light collection efficiency of the heterojunction battery can be better improved.

[0086] In detail, the oxidation process includes:

[0087] Providing N portions of hydrochloric acid solution, where N is an integer greater than or equal to 2;

[0088] The silicon wafer after the secondary saponification treatment is placed in a portion of the hydrochloric acid solution to obtain a hydrochloric acid solution containing the silicon wafer, and the remaining portions of the hydrochloric acid solution are added to the hydrochloric acid solution containing the silicon wafer in batches at intervals of 100s to 200s;

[0089] In the oxidation process, ozone is introduced into the hydrochloric acid solution containing the silicon wafer, and the oxidation treatment is carried out in the presence of ozone;

[0090] N=W1 / W2, W1 is the percentage of the total mass of hydrochloric acid in N parts of hydrochloric acid solution to the total mass of the oxidizing liquid used in the oxidation treatment, W2 is the percentage of the mass of hydrochloric acid in one part of hydrochloric acid solution in the oxidation treatment to the total mass of the oxidizing liquid used in the oxidation treatment, 0.16wt%≤W1≤0.21wt%, 0.0133wt%≤W2≤0.0175wt%; and / or,

[0091] The concentration of ozone in the oxidation treatment liquid is 50 ppm to 60 ppm.

[0092] Specifically, the present invention utilizes ozone in combination with hydrochloric acid to further clean the silicon wafer surface and simultaneously remove metal ions from the surface. Specifically, due to ozone's strong oxidizing properties, ozone reacts first with more active areas of the silicon wafer surface, such as rougher areas. In the presence of hydrochloric acid, ozone immediately corrodes the oxide layer. Furthermore, hydrochloric acid effectively controls the pH of the solution, stabilizing the ozone concentration. Adjusting the ozone concentration allows for control of the reaction rate.

[0093] After research, the inventors found that by adding hydrochloric acid solution in batches during the oxidation treatment process, it is beneficial to better control the pH of the oxidation treatment solution, and is more conducive to increasing the solubility of ozone in the oxidation treatment solution, thereby better improving the efficiency of the oxidation treatment.

[0094] Therefore, the present invention further limits the concentration of ozone in the oxidation treatment liquid to 50ppm to 60ppm, and limits the total mass of hydrochloric acid in N parts of hydrochloric acid solution, that is, the total mass of hydrochloric acid added during the oxidation treatment as a percentage W1 of the total mass of the oxidation treatment liquid used in the oxidation treatment, to 0.16-0.21wt%. A portion of hydrochloric acid solution is added every 100s to 200s, and the mass of hydrochloric acid in one portion of hydrochloric acid solution as a percentage W2 of the total mass of the oxidation treatment liquid used in the oxidation treatment is 0.0133-0.0175wt%. The above-mentioned portion of hydrochloric acid is added a total of N times during the oxidation treatment, where N is an integer greater than or equal to 2. Through the above-mentioned oxidation treatment, organic contamination and metal ion contamination on the surface of the silicon wafer can be decomposed more quickly, and the above-mentioned oxidation treatment has lower energy consumption and no pollutant emissions. In addition, the oxidation treatment process can also provide a 50ppm to 100nm oxide film on the silicon wafer, better protecting the silicon wafer from secondary contamination in subsequent processes.

[0095] In the passivation treatment, the present invention uses a passivation treatment liquid to perform the above-mentioned passivation treatment to remove the oxide layer, so that the silicon wafer does not absorb water and does not stick to the wafer, and at the same time makes the silicon wafer hydrophobic. Furthermore, the passivation treatment liquid includes hydrofluoric acid, an anti-water absorption passivation additive and water, and the mass ratio of hydrofluoric acid to the anti-water absorption passivation additive in the passivation treatment liquid is (3.3 to 9.6): (2.2 to 6.4). For example, the mass ratio of hydrofluoric acid to the anti-water absorption passivation additive in the passivation treatment liquid includes but is not limited to 3.3:2.2, 5:3, 7:4, 9:5, 9.6:6.4 or a range consisting of any two of them. By using a passivation treatment liquid with the above-mentioned ratio for passivation treatment, the oxide layer on the surface of the silicon wafer can be more effectively removed to obtain a clean silicon wafer, which is beneficial to the subsequent preparation of heterojunction batteries.

[0096] Furthermore, the anti-water absorption passivation additive includes a chelating agent, a surfactant, a penetrant, and an acidity regulator.

[0097] Wherein, the solvent of the anti-water absorption passivation additive is deionized water.

[0098] To further improve the cleaning efficiency of silicon wafers, the present invention incorporates a chelating agent into the anti-water absorption passivation additive. During the passivation process, the chelating agent not only chelates metals, effectively removing metals from the silicon wafer surface, reducing the total metal content to less than 20 ppb, but also catalyzes the reaction between hydrofluoric acid and the silicon dioxide generated by oxidation on the silicon wafer surface during the passivation process, accelerating the removal of the silicon dioxide. Specifically, the chelating agent of the present invention comprises at least one of a polyphosphate and an aminocarboxylic acid, with the mass percentage of the chelating agent in the passivation solution ranging from 0.8 wt% to 1.7 wt%. Using this chelating agent in the above ratio for passivation can significantly improve the efficiency of the passivation process.

[0099] The present invention also incorporates a surfactant into the anti-water absorption passivation additive. The surfactant significantly reduces the surface tension of water and other cleaning fluids, making it easier to wet the silicon wafer surface. This helps the cleaning fluid more effectively penetrate into these fine structures, particularly those with micropores and cracks, thereby improving the cleaning effect. The surfactant comprises at least one of an isomeric alcohol polyoxyethylene ether and glutaric acid, and the surfactant is present in the passivation treatment solution in an amount of 0.5 to 1.6 weight percent. Using this surfactant in the passivation treatment improves the cleanliness of the silicon wafer surface.

[0100] The present invention also incorporates a penetrant into the anti-water absorption passivation additive to further reduce the surface tension of the passivation solution. Specifically, the penetrant comprises at least one of a fatty alcohol polyoxyethylene ether and a long-chain alkyl chlorosilane, with the penetrant content in the passivation solution ranging from 0.4 to 1.1 weight percent. Using this penetrant in this ratio for passivation treatment facilitates thorough cleaning of the silicon wafer surface.

[0101] Furthermore, considering the limited ionization degree of hydrofluoric acid in water, the present invention also incorporates a hydrofluoric acid ionization additive, also known as an acidity regulator, into the anti-water absorption passivation additive. This acidity regulator contains a substance that can efficiently ionize fluoride ions, far exceeding the ionization degree of hydrofluoric acid in aqueous solution, thereby further promoting the reaction between hydrofluoric acid and silicon wafers. The acidity regulator comprises at least one of acetic acid and citric acid, and the acidity regulator is present in the passivation solution at a concentration of 0.5 to 2 weight percent. Using this surfactant in the passivation treatment improves the reaction efficiency between hydrofluoric acid and the silicon wafer surface, resulting in a clean silicon wafer.

[0102] Furthermore, the present invention controls the treatment temperature of the primary saponification treatment to be 55° C. to 70° C., and the treatment time to be 200s to 350s.

[0103] In another specific embodiment, the treatment temperature of the secondary saponification treatment is 55° C. to 70° C., and the treatment time is 200 s to 280 s.

[0104] The present invention limits the treatment temperature and treatment time of the primary saponification treatment and the secondary saponification treatment, thereby better improving the efficiency of the primary saponification treatment and the secondary saponification treatment, and is more conducive to removing organic impurities from the silicon wafer.

[0105] In the oxidation treatment, the present invention further limits the treatment temperature of the oxidation treatment to 23° C. to 26° C. and the treatment time to 170s to 280s, which is more conducive to the oxidation treatment and further more conducive to improving the efficiency of silicon wafer cleaning.

[0106] In the passivation treatment, the present invention further limits the treatment temperature of the passivation treatment to 23° C. to 26° C. and the treatment time to 180s to 290s, which is more conducive to the synergistic effect of the components in the passivation treatment solution and is more conducive to improving the effect of the passivation treatment.

[0107] In addition, in order to obtain dry silicon wafers, the present invention further performs a drying process on the silicon wafers, and further limits the drying process to a processing temperature of 65° C. to 85° C. and a processing time of 600 s to 1000 s.

[0108] A second aspect of the present invention provides a silicon wafer, which is processed using the above-mentioned silicon wafer cleaning method, and the surface of the silicon wafer has a high degree of cleanliness.

[0109] A third aspect of the present invention provides a heterojunction battery, which uses the above-mentioned silicon wafer or the silicon wafer obtained by the above-mentioned silicon wafer cleaning method as a substrate. The heterojunction battery also includes a first functional layer, which is located on one side of the substrate and forms a PN junction with the substrate. It also includes a second functional layer located on the side of the substrate away from the first functional layer, and the second functional layer constitutes the back surface field of the substrate. It also includes an electrode structure located on the side of the first functional layer and the second functional layer away from the substrate.

[0110] In another specific embodiment, the heterojunction battery further includes an electrode structure located on a side of the first functional layer or the second functional layer facing away from the substrate.

[0111] The present invention does not specifically limit the first functional layer and the second functional layer. For example, the first functional layer includes: a first intrinsic semiconductor layer, a first doped semiconductor layer, and a first transparent conductive layer stacked in sequence.

[0112] Specifically, the second functional layer includes: a second intrinsic semiconductor layer, a second doped semiconductor layer and a second transparent conductive layer stacked in sequence.

[0113] The first transparent conductive layer includes at least one of indium tin oxide (ITO), fluorine-doped tin oxide (FTO), and aluminum zinc oxide (AZO).

[0114] The second transparent conductive layer includes at least one of indium tin oxide (ITO), fluorine-doped tin oxide (FTO), and aluminum zinc oxide (AZO).

[0115] Furthermore, the first doped semiconductor layer includes at least one of single crystal silicon, polycrystalline silicon, amorphous silicon, cadmium telluride, an organic semiconductor material, copper indium gallium selenide, and nanoporous titanium dioxide.

[0116] The second doped semiconductor layer includes at least one of single crystal silicon, polycrystalline silicon, amorphous silicon, cadmium telluride, an organic semiconductor material, copper indium gallium selenide, and nanoporous titanium dioxide.

[0117] The electrode structure includes at least one of silver (Ag), copper (Cu), and aluminum (Al).

[0118] The heterojunction battery provided by the present invention has high photoelectric conversion efficiency and can provide a stable power supply.

[0119] The present invention also provides an electrical device comprising the heterojunction battery. By using the heterojunction battery, the electrical device can operate stably and have a long service life.

[0120] The technical solution of the present invention is further described below with reference to specific embodiments.

[0121] Example 1

[0122] The reagents used in this example are as follows:

[0123] Glue remover: NY-126, Wuhan Yitian;

[0124] Chelating agent: aminocarboxylic acid CHN2O8;

[0125] Surfactant: Isomeric alcohol polyoxyethylene ether, C 13 H 27 O(CH2CH2O)5H;

[0126] Penetrant: Fatty alcohol polyoxyethylene ether C 13 O(CH2CH2O)6H.

[0127] like Figure 1 As shown, the silicon wafer cleaning method of this embodiment includes the following steps:

[0128] 1) The silicon wafer was ultrasonically washed at 25° C. for 200 s, and then debonded with a debonding agent at 25° C. for 155 s. After the debonding, the silicon wafer was first washed with water at 25° C. for 200 s.

[0129] 2) The silicon wafer after the first water washing treatment is placed in a primary saponification treatment solution including 16% by mass hydrogen peroxide and 0.5% by mass sodium hydroxide at 60° C. for a primary saponification treatment for 220 seconds. After the primary saponification treatment, a second water washing treatment is performed at 26° C. for 240 seconds.

[0130] 3) The silicon wafer after the second water washing treatment is placed in a secondary saponification treatment solution including 8.5% by mass hydrogen peroxide and 0.3% by mass sodium hydroxide at 65° C. for a secondary saponification treatment for 225 seconds. After the secondary saponification treatment, a third water washing treatment is performed at 26° C. for 240 seconds.

[0131] 4) A hydrochloric acid solution having a mass percentage of 0.186 wt % was divided into 12 portions, where the mass of the hydrochloric acid in each portion of the hydrochloric acid solution accounted for 0.0155 wt % of the total mass of the oxidation solution used in the oxidation treatment. The silicon wafer after the third water washing treatment was placed in one portion of the hydrochloric acid solution, and then 58 ppm of ozone was introduced to obtain an oxidation solution. The oxidation treatment was carried out in the oxidation solution at 23° C. for 180 s, and then the remaining hydrochloric acid was added to the oxidation solution in batches at intervals of 120 s. After the oxidation treatment, a third water washing treatment was carried out at 23° C. for 180 s.

[0132] 5) The silicon wafer after the fourth water washing treatment is passivated at 24° C. for 210 seconds using a passivation treatment solution, wherein the passivation treatment solution comprises 3.5% by mass of hydrofluoric acid, 0.8% by mass of a chelating agent, 0.6% by mass of a surfactant, 0.5% by mass of a fatty alcohol polyoxyethylene ether, and 0.7% by mass of an acidity regulator, acetic acid; and the silicon wafer after the passivation treatment is ultrasonically washed at 23° C. for 225 seconds.

[0133] 6) The silicon wafer after ultrasonic water washing was subjected to a slow pulling treatment at 23° C., and then dried at 70° C. for 730 s to obtain a cleaned silicon wafer.

[0134] 7) The cleaned silicon wafers are packaged and transported to a battery production base for texturing.

[0135] Example 2

[0136] This embodiment is substantially the same as embodiment 1, except that the primary saponification treatment solution in this embodiment includes 18% by weight of hydrogen peroxide and 0.6% by weight of sodium hydroxide.

[0137] Example 3

[0138] This embodiment is substantially the same as embodiment 1, except that the secondary saponification treatment solution in this embodiment includes 10% by weight of hydrogen peroxide and 0.3% by weight of sodium hydroxide.

[0139] Example 4

[0140] This embodiment is basically the same as Example 1, except that, in this embodiment, the mass percentage of the anti-water absorption passivation additive is 2.9%, the mass percentage of the chelating agent polyphosphate in the passivation treatment solution is 0.8%, the mass percentage of the surfactant isomeric alcohol polyoxyethylene ether in the passivation treatment solution is 1.0%; the mass percentage of the penetrant fatty alcohol polyoxyethylene ether in the passivation treatment solution is 0.5%; and the mass percentage of the acidity regulator citric acid in the passivation treatment solution is 0.6%.

[0141] Example 5

[0142] This embodiment is substantially the same as embodiment 1, except that the primary saponification treatment solution in this embodiment includes 12% by weight of hydrogen peroxide and 0.2% by weight of sodium hydroxide.

[0143] Example 6

[0144] This embodiment is substantially the same as embodiment 1, except that the secondary saponification treatment solution in this embodiment includes 7.5% by weight of hydrogen peroxide and 0.1% by weight of sodium hydroxide.

[0145] Example 7

[0146] This embodiment is substantially the same as embodiment 1, except that the anti-water absorption passivation additive in this embodiment does not include an acidic regulator.

[0147] Example 8

[0148] This embodiment is substantially the same as embodiment 1, except that the anti-water absorption passivation additive in this embodiment does not include a chelating agent.

[0149] Comparative Example 1

[0150] This comparative example is basically the same as Example 1, except that the mass percentage of hydrogen peroxide in the primary saponification treatment liquid used in the primary saponification treatment of this comparative example is the same as that used in the secondary saponification treatment, and the mass percentage concentration is 16%.

[0151] Comparative Example 2

[0152] This comparative example is substantially the same as Example 1, except that this comparative example does not include a secondary saponification treatment.

[0153] Test example

[0154] The surface reflectivity of the cleaned silicon wafers in Examples 1-8 and Comparative Examples 1-2 was tested using a standard 8-degree (D8) reflectivity tester. The test results are shown in Table 1.

[0155] The silicon wafers in Examples 1-8 and Comparative Examples 1-2 were tested for dense pitting defects using photoluminescence (PL). The PL test system, which uses light irradiation to detect cracks, voids, microcrystallization, impurities, and other hard spots, was used. The PL instrument, manufacturer and model: Kairuida BTI-W3, was used. The test results are shown in Table 1 (Dense Pitting Defect Incidence).

[0156] Table 1

[0157]

[0158]

[0159] It can be seen from the above table that compared with comparative examples 1-2, the silicon wafers in Examples 1-8 have better cleaning effects, so that the silicon wafers after texturing have lower surface reflectivity and lower incidence of dense pitting defects. Therefore, the silicon wafer cleaning method of the present invention can obtain silicon wafers with higher cleanliness, which is conducive to the preparation of heterojunction batteries with higher efficiency.

[0160] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A silicon wafer cleaning method, characterized in that: The following steps are involved: The silicon wafer is sequentially subjected to the following treatments: a primary saponification treatment using a primary saponification treatment solution, a secondary saponification treatment using a secondary saponification treatment solution, an oxidation treatment, and a passivation treatment to obtain a cleaned silicon wafer; The primary saponification treatment liquid includes hydrogen peroxide; The secondary saponification treatment solution includes hydrogen peroxide; The mass percentage of hydrogen peroxide in the primary saponification treatment liquid is greater than the mass percentage of hydrogen peroxide in the secondary saponification treatment liquid.

2. The silicon wafer cleaning method according to claim 1, wherein: The ratio of the mass percentage of hydrogen peroxide in the first saponification treatment liquid to the mass percentage of hydrogen peroxide in the second saponification treatment liquid is (1.4-1.9):1; and / or, The mass percentage of hydrogen peroxide in the primary saponification treatment liquid is 15.5wt% to 21wt%; and / or, The mass percentage of hydrogen peroxide in the secondary saponification treatment liquid is 8.3wt% to 15wt%; and / or, The primary saponification treatment liquid further comprises alkali, and the mass percentage of alkali in the primary saponification treatment liquid is 0.3wt% to 0.9wt%; and / or, The secondary saponification treatment liquid further comprises alkali, and the mass percentage of the alkali in the secondary saponification treatment liquid is 0.2 wt % to 0.7 wt %.

3. The silicon wafer cleaning method according to claim 2, wherein: The silicon wafer cleaning method further comprises: performing a degumming treatment and at least one first water washing treatment on the silicon wafer in sequence, and then performing the saponification treatment; and / or, After the primary saponification treatment, the silicon wafer is subjected to at least one second water washing treatment, and then subjected to the secondary saponification treatment; and / or, After the secondary saponification treatment, the silicon wafer is subjected to at least one third water washing treatment, and then subjected to the oxidation treatment; and / or, After the oxidation treatment, the silicon wafer is subjected to at least one fourth water washing treatment, and then the passivation treatment is performed; and / or, The silicon wafer cleaning method further includes: after the passivation treatment, performing a texturing treatment on the silicon wafer to obtain the cleaned silicon wafer.

4. The silicon wafer cleaning method according to any one of claims 1 to 3, characterized in that: After the passivation treatment, the silicon wafer is subjected to texturing treatment to obtain the cleaned silicon wafer, which specifically includes: after the passivation treatment, the silicon wafer is subjected to slow pulling treatment and drying treatment in sequence, and then subjected to texturing treatment to obtain the cleaned silicon wafer.

5. The silicon wafer cleaning method according to claim 4, wherein: The oxidation treatment process includes: Providing N portions of hydrochloric acid solution, where N is an integer greater than or equal to 2; placing the silicon wafer after the secondary saponification treatment in one portion of the hydrochloric acid solution to obtain a hydrochloric acid solution containing the silicon wafer, and adding the remaining portions of the hydrochloric acid solution to the hydrochloric acid solution containing the silicon wafer in batches at intervals of 100s to 200s; Wherein, during the oxidation treatment, ozone is introduced into the hydrochloric acid solution containing the silicon wafer, and the oxidation treatment is performed in the presence of the ozone; N=W1 / W2, W1 is the percentage of the total mass of the hydrochloric acid in the N parts of hydrochloric acid solution to the total mass of the oxidizing liquid used in the oxidation treatment, W2 is the percentage of the mass of the hydrochloric acid in one part of the hydrochloric acid solution in the oxidation treatment to the total mass of the oxidizing liquid used in the oxidation treatment, 0.16wt%≤W1≤0.21wt%, 0.0133wt%≤W2≤0.0175wt%; and / or, The concentration of ozone in the oxidation treatment liquid is 50ppm to 60ppm.

6. The silicon wafer cleaning method according to claim 5, characterized in that: The passivation treatment is performed using a passivation treatment solution, wherein the passivation treatment solution includes hydrofluoric acid, an anti-water absorption passivation additive, and water; The mass percentage of the hydrofluoric acid and the anti-water absorption passivation additive in the passivation treatment solution is (3.3-9.6): (2.2-6.4).

7. The silicon wafer cleaning method according to claim 6, wherein: The anti-water absorption passivation additives include chelating agents, surfactants, penetrants, and acidity regulators; The chelating agent comprises at least one of polyphosphate and aminocarboxylic acid, and the mass percentage of the chelating agent in the passivation treatment solution is 0.8wt% to 1.7wt%; and / or, The surfactant comprises at least one of isomeric alcohol polyoxyethylene ether and glutaric acid, and the mass percentage of the surfactant in the passivation treatment solution is 0.5wt% to 1.6wt%; and / or, The penetrant includes at least one of fatty alcohol polyoxyethylene ether and long-chain alkyl chlorosilane, and the mass percentage of the penetrant in the passivation treatment solution is 0.4wt% to 1.1wt%; and / or, The acidity regulator comprises at least one of acetic acid and citric acid, and the mass percentage of the acidity regulator in the passivation treatment solution is 0.5wt% to 2wt%; and / or, The treatment temperature of the primary saponification treatment is 55° C. to 70° C., and the treatment time is 200s to 350s; and / or, The treatment temperature of the secondary saponification treatment is 55° C. to 70° C., and the treatment time is 200s to 280s; and / or, The oxidation treatment temperature is 23° C. to 26° C., and the treatment time is 170s to 280s; and / or, The passivation treatment has a treatment temperature of 23° C. to 26° C. and a treatment time of 180s to 290s; and / or, The drying process has a treatment temperature of 65° C. to 85° C. and a treatment time of 600s to 1000s.

8. A silicon wafer, characterized in that: The silicon wafer is obtained by processing the silicon wafer cleaning method according to any one of claims 1 to 7.

9. A heterojunction battery, characterized in that: include: A silicon wafer obtained by the silicon wafer cleaning method according to any one of claims 4 to 7 or a silicon wafer according to claim 8 is used as a substrate; the substrate has two opposite sides; A 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; a second functional layer located on a side of the substrate facing away from the first functional layer; the second functional layer is configured to: constitute a back surface field of the substrate; The electrode structure is located on a side of the first functional layer and / or the second functional layer facing away from the substrate.

10. An electrical device, characterized in that: The electrical device includes the heterojunction battery according to claim 9.

Images