A texturing additive composition for silicon wafers and a texturing solution

Abstract

A texturing additive composition for silicon wafer and a texturing solution, the texturing additive composition comprises the following components: nucleating agent 0.01-7.5 wt%; etching control agent 0.05-5.5 wt%; dispersing agent 0.0001-3.5 wt%; surfactant 0.0-2.0 wt%; pH regulator 0.0-5.0 wt%; water. The texturing additive composition and the texturing solution can match the special thin film deposition requirement of heterojunction solar cells, and the synergistic effect of the components in the texturing additive composition can realize the optimization of the structure combination of the textured surface on the basis of ensuring the full coverage rate of the textured surface, so that the pyramid distribution of the textured surface is uniform and the apparent reflectivity of the silicon wafer surface is lower. The structure combination of the textured surface is beneficial to the deposition of amorphous silicon thin film in the next process of the heterojunction solar cell, and has excellent light trapping property.

Description

Technical Field

[0001] The present application relates to the technical field of solar cell production and application, in particular to a texturing additive composition and a texturing solution for silicon wafers. Background Art

[0002] Heterojunction solar cells are a new type of high-efficiency solar cell developed by Sanyo Corporation of Japan by introducing thin-film deposition technology into crystalline silicon solar cells. Combined with IBC (Interdigitated Back Contact) technology, heterojunction solar cells have become one of the most efficient crystalline silicon cells currently available and hold broad development prospects. Thin-film deposition technology is key to ensuring the photoelectric conversion efficiency and stability of heterojunction solar cells. Due to the requirements of thin-film deposition technology, heterojunction solar cells have more stringent requirements for the textured surface of the single-crystalline silicon substrate than traditional solar cells. Single-crystalline silicon is the primary material for solar cell manufacturing. Textured surface treatment not only reduces surface reflectivity but also obliquely inclines light entering the cell, increasing the optical path, thereby effectively improving the cell's photoelectric conversion efficiency.

[0003] Texturing is a process that uses an alkaline solution to anisotropically etch the different crystal planes of single-crystalline silicon, thereby forming a pyramid texture on the surface of the silicon wafer. The uniformity and size of the texture pyramids on the surface of crystalline silicon have a significant impact on the subsequent amorphous silicon thin film deposition process. It is difficult for amorphous silicon thin film to be uniformly deposited at the base of pyramids that are too small; and due to the effect of stress, microcracks are easily generated, resulting in a poor passivation effect. Therefore, increasing the size of the pyramids can effectively improve the open-circuit voltage of silicon heterojunction solar cells. At the same time, good pyramid uniformity can improve light trapping, thereby increasing the short-circuit current of the solar cell, thereby improving the photoelectric conversion efficiency of the silicon heterojunction solar cell. In addition, because the coating processes used by different solar cell manufacturers are somewhat different, in order to achieve the best results, the texture pyramid sizes corresponding to different coating processes vary greatly.

[0004] Existing texturing solutions struggle to simultaneously achieve both uniformity of the textured surface and controllable pyramid sizes. Therefore, developing novel texturing additive compositions that can achieve both adjustable pyramid size and excellent texture uniformity is crucial for the development of silicon heterojunction solar cells. Summary of the Invention

[0005] The present application provides a texturing additive composition for silicon wafers, comprising the following components:

[0006] Nucleating agent 0.01-7.5 wt%;

[0007] Etching control agent 0.05-5.5 wt%;

[0008] Dispersant 0.0001-3.5 wt%;

[0009] Surfactant 0.0-2.0 wt%;

[0010] pH adjuster 0.0-5.0 wt%;

[0011] water;

[0012] Wherein, the sum of the weight percentages of the components of the texturing additive composition is 100 wt%;

[0013] The nucleating agent is a polysaccharide compound, the molecular weight distribution range of the polysaccharide compound is D1 to D2, and the polydispersity index is 1.00-1.90; wherein D2 and D1 are both within the range of 1×10 2 -1×10 7 Daltons, and D2:D1 is (5-50):1, preferably (5-20):1.

[0014] In one embodiment, the molecular weight distribution range of the polysaccharide compound is 1×10 3 -1×10 4 Dalton; or

[0015] The molecular weight distribution range of the polysaccharide compound is 1×10 4 -1×10 5 Dalton; or

[0016] The molecular weight distribution range of the polysaccharide compound is 1×10 5 -1×10 6 Dalton; or

[0017] The molecular weight distribution range of the polysaccharide compound is 1×10 6 -1×10 7 Dalton.

[0018] In one embodiment, the polysaccharide compound is selected from one or more of carboxymethyl cellulose, hydroxyethyl cellulose, sodium carboxymethyl starch, water-soluble starch, xanthan gum, carrageenan, locust bean gum, sesbania gum and carrageenan;

[0019] Preferably, the polysaccharide compound is selected from one or more of sodium carboxymethyl starch, carrageenan, locust bean gum and xanthan gum.

[0020] In one embodiment, the polysaccharide compound is prepared as follows:

[0021] The polysaccharide raw material is hydrolyzed under acidic conditions, and then the molecular weight distribution range of the hydrolyzed polysaccharide raw material is narrowed to obtain the polysaccharide compound.

[0022] In one embodiment, the molecular weight distribution range is narrowed by dialysis, and the dialysis comprises:

[0023] The first dialysis was performed using a first dialysis bag with a molecular weight cut-off of D3, and the second dialysis was performed using a second dialysis bag with a molecular weight cut-off of D4.

[0024] In one embodiment, D3 is located at 1×10 2 -1×10 5 Between Dalton, D4 is located at 1×10 3 -1×10 6 Dalton between.

[0025] In one embodiment, the texturing additive composition further comprises an auxiliary nucleating agent in an amount of 0.00001-3.5 wt %, based on the total weight of the texturing additive composition.

[0026] In one embodiment, the auxiliary nucleating agent is selected from one or more of sodium silicate, sodium chloride, potassium chloride, sodium carbonate, potassium carbonate, lignin and its derivatives, hematoxylin and its derivatives, and humic acid and its extracts.

[0027] In one embodiment, the etching control agent is selected from polyethylene glycol, polypropylene glycol, polyethylene glycol monomethyl ether, polyethylene glycol dimethyl ether, polyethylene imine, polyvinyl alcohol, cyclohexanediol, 3-methyl-1,5-pentanediol, N - one or more of methyl pyrrolidone, polyvinyl pyrrolidone, chitosan, chitosan oligosaccharide and sorbitol; preferably, the etching control agent is selected from one or more of polyethylene glycol monomethyl ether, 3-methyl-1,5-pentanediol, polyethyleneimine and chitosan oligosaccharide.

[0028] In one embodiment, the dispersant is selected from one or more of sodium lactate, sodium benzoate, sodium tripolyphosphate, sodium hexametaphosphate, sodium 5-nitroguaiacol, sodium citrate, sodium gluconate, sodium methylene bisnaphthalene sulfonate, sodium carbonate, sodium acetate and sodium tartrate; preferably, the dispersant is selected from one or more of sodium hexametaphosphate, sodium citrate and sodium benzoate.

[0029] In one embodiment, the surfactant is selected from one or more of disodium lauryl sulfosuccinate, fatty alcohol polyoxyethylene ether, fatty acid methyl ester ethoxylate, fatty acid methyl ester ethoxylate sulfonate, disodium coconut oil monoethanolamide sulfosuccinate, sodium lauryl sulfate, sodium dodecylbenzenesulfonate and sodium oleate; preferably, the surfactant is selected from one or more of fatty alcohol polyoxyethylene ether, sodium lauryl sulfate and sodium dodecylbenzenesulfonate.

[0030] In one embodiment, the pH adjuster is selected from one or more of sodium hydroxide, potassium hydroxide, propionic acid, acetic acid, formic acid, maleic acid, maleic anhydride, lauryl ether phosphate, cocoyl monoethanolamide, cocamidopropyl betaine and cocamidopropyl hydroxysulfonate; preferably, the pH adjuster is selected from one or more of sodium hydroxide, acetic acid and lauryl ether phosphate.

[0031] The present application also provides a texturing solution comprising an alkali, the texturing additive composition of the present application and water.

[0032] In one embodiment, the base is an inorganic base and / or an organic base; preferably, the inorganic base is KOH and / or NaOH, and the organic base is tetramethylguanidine and / or tetraethylammonium hydroxide.

[0033] In one embodiment, the amount of the texturing additive composition is 0.05-1.5 wt %, based on the total weight of the texturing solution;

[0034] The amount of the alkali is 0.5-5.5 wt %, based on the total weight of the texturing solution.

[0035] The texturing additive composition and texturing solution described in this application can meet the specific thin-film deposition requirements of heterojunction solar cells. The synergistic effect of the various components in the texturing additive composition optimizes the texture structure while ensuring the full coverage of the texture surface. This results in an even distribution of texture pyramids, good texture uniformity, and lower apparent reflectivity on the silicon wafer surface. This texture structure combination facilitates the deposition of amorphous silicon thin films in the next step of the heterojunction solar cell process, while also exhibiting excellent light trapping properties, thereby achieving a stable and reliable heterojunction solar cell. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 The SEM image of the textured surface of the silicon wafer obtained in Example 1 is shown;

[0037] Figure 2 The SEM image of the textured surface of the silicon wafer obtained in Example 2 is shown;

[0038] Figure 3 The SEM image of the textured surface of the silicon wafer obtained in Example 3 is shown;

[0039] Figure 4 The SEM image of the textured surface of the silicon wafer obtained in Example 4 is shown;

[0040] Figure 5 The SEM image of the textured surface of the silicon wafer obtained in Comparative Example 1 is shown;

[0041] Figure 6 The SEM image of the textured surface of the silicon wafer obtained in Comparative Example 2 is shown;

[0042] Figure 7 The SEM image of the textured surface of the silicon wafer obtained in Example 5 is shown;

[0043] Figure 8 The SEM image of the textured surface of the silicon wafer obtained in Example 6 is shown;

[0044] Figure 9 The SEM image of the textured surface of the silicon wafer obtained in Example 7 is shown;

[0045] Figure 10 The molecular weight distribution curve of the xanthan gum in Comparative Example 1 is shown;

[0046] Figure 11 The molecular weight distribution curve of xanthan gum obtained by preliminary hydrolysis in Comparative Example 2 is shown;

[0047] Figure 12 The molecular weight distribution curve of the xanthan gum obtained in Example 1 is shown. DETAILED DESCRIPTION

[0048] The present application will be further described in detail below through the accompanying drawings and examples, through which the features and advantages of the present application will become more clear and distinct.

[0049] The word "exemplary" is used exclusively herein to mean "serving as an example, example, or illustration." Any embodiment described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments. Although various aspects of the embodiments are shown in the drawings, the drawings are not necessarily drawn to scale unless otherwise indicated.

[0050] In addition, the technical features involved in different embodiments of the present application described below can be combined with each other as long as they do not conflict with each other.

[0051] The present application provides a texturing additive composition for silicon wafers, comprising the following components:

[0052] Nucleating agent 0.01-7.5 wt%;

[0053] Etching control agent 0.05-5.5 wt%;

[0054] Dispersant 0.0001-3.5 wt%;

[0055] Surfactant 0.0-2.0 wt%;

[0056] pH adjuster 0.0-5.0 wt%;

[0057] water;

[0058] Wherein, the sum of the weight percentages of the components of the texturing additive composition is 100 wt%;

[0059] The nucleating agent is a polysaccharide compound, the molecular weight distribution range of the polysaccharide compound is D1 to D2, and the polydispersity index is 1.00-1.90; wherein D2 and D1 are both within the range of 1×10 2 -1×10 7 Daltons, and D2:D1 is (5-50):1, preferably (5-20):1.

[0060] In this application, "molecular weight distribution range D1 to D2" means that in the molecular weight distribution curve of the polysaccharide compound, the total mass percentage of molecules with a molecular weight lower than D1 is less than 10%, even less than 5%, or even less than 1% of the total molecules; and the total mass percentage of molecules with a molecular weight higher than D2 is also less than 10%, even less than 5%, or even less than 1%. In other words, the total mass percentage of molecules with a molecular weight between D1 and D2 accounts for more than 85%, even more than 90%, or even more than 95% of the total molecules.

[0061] The polysaccharide compound used as the nucleating agent of the present application has a narrow molecular weight distribution (polydispersity index) and a relatively small molecular weight distribution range. The inventors of the present application unexpectedly discovered that when a polysaccharide compound with a narrow molecular weight distribution range is used as a nucleating agent for texturing a single crystal silicon wafer, a pyramid velvet with very good velvet uniformity can be obtained. Moreover, by adjusting the values ​​of D1 and D2 in the molecular weight distribution range, the size of the pyramid velvet can also be adjusted, that is: when D1 and D2 are larger, a smaller-sized pyramid velvet is obtained; when D1 and D2 are smaller, a larger-sized pyramid velvet can be obtained. Therefore, the upper and lower limits of the appropriate molecular weight distribution range can be selected according to different needs.

[0062] In one embodiment, the molecular weight distribution range of the polysaccharide compound is 1×10 3 -1×10 4 Alternatively, the molecular weight distribution range of the polysaccharide compound is 1×10 4 -1×10 5 Alternatively, the molecular weight distribution range of the polysaccharide compound is 1×10 5 -1×10 6 Alternatively, the molecular weight distribution range of the polysaccharide compound is 1×10 6 -1×10 7 Within this molecular weight distribution range, the polysaccharide compound has a unimodal molecular weight distribution curve, and a relatively narrow polydispersity index (PDI) of 1.00-1.90, such as 1.05-1.70, such as 1.10-1.60.

[0063] The nucleating agent is a polysaccharide compound with a specific molecular weight distribution range and molecular weight distribution. The structural characteristics of this type of compound are high molecular weight compounds with multiple hydroxyl groups. During the texturing process, the hydroxyl groups are adsorbed on the surface of the silicon wafer, which can hinder the OH in the alkaline solution from - The ions react with the silicon wafer, forming fuzzy spots at the adsorption sites.

[0064] In one embodiment, the polysaccharide compound is selected from one or more of carboxymethyl cellulose, hydroxyethyl cellulose, sodium carboxymethyl starch, water-soluble starch, xanthan gum, carrageenan, locust bean gum, sesbania gum and carrageenan.

[0065] Preferably, the polysaccharide compound is selected from one or more of sodium carboxymethyl starch, carrageenan, locust bean gum and xanthan gum.

[0066] In one embodiment, the polysaccharide compound used in the present application can be prepared as follows:

[0067] The polysaccharide raw material is hydrolyzed under acidic conditions, and then the molecular weight distribution range of the hydrolyzed polysaccharide raw material is narrowed to obtain the polysaccharide compound.

[0068] The polysaccharide raw materials used in this application are all commercially available USP grade or ACS grade. After the applicant purchased the polysaccharide raw materials, the molecular weight distribution was measured. The molecular weight distribution range of the polysaccharide raw materials met the upper limit of not less than 1×10 7 Dalton, it can be ensured that the polysaccharide compound can be prepared by the above method.

[0069] The preliminary hydrolysis process can be carried out as follows: the nucleating agent raw material (polysaccharide compound raw material) is completely dissolved in an inorganic strong acid, such as an inorganic strong acid with a concentration of 0.01-1.0 mol / L (such as hydrochloric acid, sulfuric acid, etc.), and heated at a certain temperature (such as 50-80°C) for a period of time (such as 1-24 hours) to perform preliminary hydrolysis. After hydrolysis, the solution is adjusted to a neutral pH with an alkali such as NaOH solution or KOH solution.

[0070] After the initial hydrolysis, the molecular weight distribution range is narrowed to obtain the polysaccharide compound used as a nucleating agent in the present application. The molecular weight distribution range can be narrowed by separation methods such as extraction, column chromatography, electrophoresis, centrifugation, and recrystallization. Dialysis can be performed using a single dialysis process, and the polysaccharide compound retained in the dialysis bag after dialysis is the polysaccharide compound used as a nucleating agent in the present application.

[0071] Alternatively, the first dialysis bag with a molecular weight cut-off of D3 may be used to perform the first dialysis, and the second dialysis bag with a molecular weight cut-off of D4 may be used to perform the second dialysis. Alternatively, the first dialysis bag with a molecular weight cut-off of D3 may be used to perform the first dialysis, and the second dialysis bag with a molecular weight cut-off of D4 may be used to perform the second dialysis. Alternatively, the second dialysis bag with a molecular weight cut-off of D4 may be used to perform the second dialysis, and the solution in the first dialysis bag may be transferred to the second dialysis bag with a molecular weight cut-off of D4 and then dialyzed.

[0072] In one embodiment, D3 is located at 1×10 2 -1×10 5 Between Dalton, D4 is located at 1×10 3 -1×10 6 Dalton between.

[0073] In the texturing additive composition of the present application, the amount of the nucleating agent is 0.01-7.5 wt %, such as 0.1-5.0 wt %, such as 0.2-4.0 wt %, based on the total weight of the texturing additive composition.

[0074] In one embodiment, the texturing additive composition further includes an auxiliary nucleating agent in an amount of 0.00001-3.5 wt %, for example, 0.05-3 wt %, for example, 0.1-2 wt %, based on the total weight of the texturing additive composition. The auxiliary nucleating agent is selected from one or more of sodium silicate, sodium chloride, potassium chloride, sodium carbonate, potassium carbonate, lignin and its derivatives, hematoxylin and its derivatives, and humic acid and its extracts. The auxiliary nucleating agent helps the nucleating agent to be more evenly distributed on the surface of the silicon wafer, thereby improving the nucleation rate.

[0075] In one embodiment, the etching control agent is selected from polyethylene glycol, polypropylene glycol, polyethylene glycol monomethyl ether, polyethylene glycol dimethyl ether, polyethylene imine, polyvinyl alcohol, cyclohexanediol, 3-methyl-1,5-pentanediol, N-One or more of methyl pyrrolidone, polyvinyl pyrrolidone, chitosan, chitosan oligosaccharide and sorbitol; preferably, the etching control agent is selected from one or more of polyethylene glycol monomethyl ether, 3-methyl-1,5-pentanediol, polyethyleneimine and chitosan oligosaccharide. The function of the etching control agent is to regulate the corrosion rate of the alkaline solution on the silicon wafer, which helps to anisotropically etch the single crystal silicon wafer to obtain a velvet pyramid structure. In the texturing additive composition of the present application, the amount of the etching control agent is 0.05-5.5 wt%, such as 0.1-5.0 wt%, such as 0.2-2.0 wt%, based on the total weight of the texturing additive composition.

[0076] In one embodiment, the dispersant is selected from one or more of sodium lactate, sodium benzoate, sodium tripolyphosphate, sodium hexametaphosphate, sodium 5-nitroguaiacol, sodium citrate, sodium gluconate, sodium methylene bisnaphthalene sulfonate, sodium carbonate, sodium acetate, and sodium tartrate; preferably, the dispersant is selected from one or more of sodium hexametaphosphate, sodium citrate, and sodium benzoate. In the texturing additive composition of the present application, the amount of the dispersant is 0.0001-3.5 wt%, for example, 0.05-3.0 wt%, for example, 0.1-2.5 wt%, for example, 0.2-2.0 wt%, based on the total weight of the texturing additive composition.

[0077] In one embodiment, the texturing additive composition of the present application may further contain a surfactant. The surfactant is selected from one or more of lauryl sulfosuccinate, fatty alcohol polyoxyethylene ether, fatty acid methyl ester ethoxylate, fatty acid methyl ester ethoxylate sulfonate, coconut oil monoethanolamide sulfosuccinate, sodium lauryl sulfate, sodium dodecylbenzenesulfonate and sodium oleate; preferably, the surfactant is selected from one or more of fatty alcohol polyoxyethylene ether, sodium lauryl sulfate and sodium dodecylbenzenesulfonate. In the texturing additive composition of the present application, the amount of the surfactant is 0.0-2.0 wt%, for example, 0.01-1.5 wt%, or 0.02-1.0 wt%, based on the total weight of the texturing additive composition.

[0078] In one embodiment, the texturing additive composition of the present application may further contain a pH regulator. The pH regulator is selected from one or more of sodium hydroxide, potassium hydroxide, propionic acid, acetic acid, formic acid, maleic acid, maleic anhydride, lauryl ether phosphate, cocoyl monoethanolamide, cocamidopropyl betaine and cocamidopropyl hydroxysulfonyl betaine; preferably, the pH regulator is selected from one or more of sodium hydroxide, acetic acid and lauryl ether phosphate. In the texturing additive composition of the present application, the amount of the pH regulator is 0.0-5.0 wt%, for example, 0.005-4.0 wt%, 0.01-3.0 wt%, 0.02-1.0 wt%, based on the total weight of the texturing additive composition.

[0079] As previously mentioned, existing texturing technologies are inadequate for the cleaning and texturing of heterojunction solar cells. Specifically, texturing solutions containing conventional silicon wafer texturing additive compositions produce small pyramid sizes and poor pyramid uniformity (typically ranging from 0.8 to 2 µm, with an average size of less than 1.5 µm). This hinders the deposition of amorphous silicon thin films, thereby impacting the photovoltaic conversion efficiency and stability of heterojunction solar cells. Furthermore, it is difficult to simultaneously achieve both uniformity and control of pyramid sizes. Second, existing texturing processes have long etching times. For example, patent CN102330155A has a texturing time exceeding 750 seconds, hindering production efficiency and failing to meet the demands of silicon heterojunction solar cell production and development. Third, texturing solutions containing conventional texturing additive compositions have strong adsorption properties on the silicon wafer surface, resulting in a high TOC (Total Organic Carbon) value on the wafer surface after texturing. This reduces the photovoltaic conversion efficiency of the solar cell and affects its stability and reliability.

[0080] The texturing additive composition and texturing solution described in this application can meet the specific thin-film deposition requirements of heterojunction solar cells. The synergistic effect of the various components of the texturing additive composition optimizes the texture structure while ensuring the full coverage of the texture surface. This results in an even distribution of pyramids, good texture uniformity, and lower apparent reflectivity on the silicon wafer surface. This texture structure combination facilitates the deposition of amorphous silicon thin films in the next step of the heterojunction solar cell process, while also exhibiting excellent light trapping properties, thereby achieving a stable and reliable heterojunction solar cell.

[0081] By adjusting the molecular weight distribution range of the nucleating agent, the pyramid size of the velvet surface can be controlled during texturing, resulting in small, medium, and large pyramid sizes. The average size of the small pyramids is approximately 1.4 µm, the average size of the medium pyramids is approximately 2.3 µm, and the average size of the large pyramids is 3.2 µm. Different pyramid surface sizes can be matched to different solar cell coating processes, expanding the applicability of the texturing additive composition.

[0082] The components of the texturing additive composition of the present application are highly water-soluble and have low adsorption effects on the surface of silicon wafers, making the components of the additive composition easy to clean and reducing the TOC value of the silicon wafer surface after cleaning.

[0083] When a texturing solution containing the texturing additive composition of this application is used for texturing, the required texturing time is less than 500 seconds at 75-82°C, and can be as short as 400 seconds. This compares to the average texturing time of over 500 seconds required by existing heterojunction solar cell texturing solutions. The use of this texturing additive composition can reduce texturing time, improve production efficiency, and further reduce the manufacturing cost of heterojunction solar cells.

[0084] The present application also provides a texturing solution comprising an alkali, the texturing additive composition of the present application and water.

[0085] In one embodiment, the base is an inorganic base and / or an organic base; preferably, the inorganic base is KOH and / or NaOH, and the organic base is tetramethylguanidine and / or tetraethylammonium hydroxide.

[0086] In one embodiment, the amount of the texturing additive composition is 0.05-1.5 wt %, based on the total weight of the texturing solution;

[0087] The amount of the alkali is 0.5-5.5 wt %, based on the total weight of the texturing solution.

[0088] The texturing liquid can be prepared as follows: in a texturing tank, a certain mass of inorganic alkali / organic alkali is dissolved in ultrapure water to prepare an alkali solution with a mass concentration of 0.5-5.5 wt%; then the texturing additive composition of the present application is added to the prepared alkali solution, the content of the texturing additive composition is 0.15-1.5 wt% (based on the total weight of the texturing liquid), and stirred evenly to obtain the texturing liquid.

[0089] In the present application, the above-mentioned silicon wafer can be N-type single crystal silicon or P-type single crystal silicon, etc.

[0090] Comparative Example 1

[0091] The following process steps are taken to texturing single crystal silicon wafers:

[0092] 1) Preparation of texturing additive composition: 1.5 parts of xanthan gum raw material (USP grade, purchased and tested with a molecular weight distribution range of 1×10 4 -1×10 7 , molecular weight less than 10 4 The molecules account for 1% of the total molecular mass and have a molecular weight higher than 10 7 The molecules account for 0.1% of the total molecular mass. The molecular weight distribution curve is shown in Figure 10 ; number average molecular weight is 162395; polydispersity index is 3.00; no additional treatment is performed), 0.1 parts of humic acid, 1.0 parts of polyethylene glycol monomethyl ether, 0.3 parts of 5-nitroguaiacol sodium, 0.2 parts of sodium lauryl sulfate, 0.05 parts of sodium hydroxide, 96.85 parts of ultrapure water are added to obtain a texturing additive composition.

[0093] 2) Preparation of texturing solution: dissolving 100 parts of KOH in 6900 parts of ultrapure water to obtain an alkaline solution; adding 28 parts of the texturing additive composition prepared in step 1) to the alkaline solution to obtain a texturing solution.

[0094] 3) Silicon wafer texturing: Place the clean silicon wafer in the texturing solution prepared in step 2) heated to 82°C and etch for 480 seconds.

[0095] 4) Silicon wafer cleaning: The silicon wafer after texturing in step 3) is cleaned with deionized water, and the deionized water on the surface of the silicon wafer is blown dry with high-purity nitrogen gas.

[0096] Figure 5 The SEM picture of the textured surface of the silicon wafer obtained in Comparative Example 1 is shown. The textured surface is not fully covered and cannot be completely textured.

[0097] Comparative Example 2

[0098] The difference between this comparative example and comparative example 1 lies in step 1), which is specifically:

[0099] The xanthan gum raw material in Comparative Example 1 was pretreated, that is, the xanthan gum was completely dissolved in 0.05 mol / L HCl solution, heated at 80°C for 6 h for preliminary hydrolysis, and after the hydrolysis was completed, NaOH was added to adjust the solution to neutrality to obtain a preliminary hydrolyzed xanthan gum solution, which was then concentrated, washed, and dried to obtain a preliminary hydrolyzed xanthan gum (the molecular weight distribution range of the test was 1×10 3 -1×10 7 , molecular weight less than 10 3 The molecules account for 3% of the total molecular mass and have a molecular weight higher than 10 7 The molecules account for 0.1% of the total molecular mass. The molecular weight distribution curve is shown in Figure 11 ; polydispersity index 4.05).

[0100] Prepare a texturing additive composition: add 96.85 parts of ultrapure water to 1.5 parts of preliminarily hydrolyzed xanthan gum, 0.1 part of humic acid, 1.0 part of polyethylene glycol monomethyl ether, 0.3 part of sodium 5-nitroguaiacol, 0.2 part of sodium lauryl sulfate, and 0.05 part of sodium hydroxide to obtain a texturing additive composition.

[0101] Figure 6 The SEM picture of the textured surface of the silicon wafer obtained in Comparative Example 2 is shown, showing that the pyramid sizes are unevenly distributed and the texture surface uniformity is extremely poor.

[0102] Example 1

[0103] The difference between Example 1 and Comparative Example 2 lies in step 1), which is specifically:

[0104] The xanthan gum solution that was initially hydrolyzed in Comparative Example 2 was dialyzed, that is, the xanthan gum solution that was initially hydrolyzed was placed on a 1×10 5 The first dialysis bag of Dalton was placed in a beaker with 1.5 L ultrapure water for dialysis separation. After the dialysis was completed, the solution in the first dialysis bag was transferred to a beaker with a molecular weight cut-off of 1×10 6 The second dialysis bag of Dalton was placed in a beaker with 1.5 L of ultrapure water for secondary dialysis separation. After the completion of the dialysis, the xanthan gum used as a nucleating agent in this embodiment was obtained after concentration, washing and drying (the molecular weight distribution range of the test was 1×10 5 -1×10 6 , molecular weight less than 10 5 The molecules account for 1% of the total molecular mass and have a molecular weight higher than 10 6 The molecules account for 3% of the total molecular mass. For the molecular weight distribution curve, see Figure 12 ; polydispersity index PDI is 1.31).

[0105] Prepare a texturing additive composition: add 96.85 parts of ultrapure water to 1.5 parts of xanthan gum obtained as above, 0.1 part of humic acid, 1.0 part of polyethylene glycol monomethyl ether, 0.3 parts of sodium 5-nitroguaiacol, 0.2 parts of sodium lauryl sulfate, and 0.05 parts of sodium hydroxide to obtain a texturing additive composition.

[0106] Figure 1 The SEM image of the textured surface of the silicon wafer obtained in Example 1 is shown. Compared with Comparative Example 1, the average pyramid size is larger, the texture uniformity is better, the reflectivity is lower, and the TOC value is lower than that of Comparative Example 1.

[0107] Example 2

[0108] The difference between this embodiment and embodiment 1 lies in step 1), which is specifically:

[0109] The molecular weight cut-off of the first dialysis bag in step 1) is 1×10 4 Daltons, the molecular weight cut-off of the second dialysis bag is 1×10 5 Dalton. The molecular weight distribution range of the obtained xanthan gum is 1×10 4 -1×10 5 , polydispersity index 1.22.

[0110] Figure 2 The SEM picture of the velvet surface after texturing obtained in Example 2 is shown, indicating that by adjusting the molecular weight of the nucleating agent, a large-sized pyramid velvet surface is obtained, and the velvet surface has better uniformity.

[0111] Example 3

[0112] The difference between this embodiment and embodiment 1 lies in step 1), which is specifically:

[0113] In step 1), only the molecular weight cut-off of 1×10 6 The molecular weight distribution range of the obtained xanthan gum was 1×10 6 -1×10 7 , polydispersity index 1.26.

[0114] Figure 3 The SEM picture of the textured surface of the silicon wafer obtained in Example 3 is shown, indicating that by adjusting the molecular weight of the nucleating agent, a small-sized pyramid texture can be obtained, and the texture uniformity is better.

[0115] Example 4

[0116] The difference between this embodiment and embodiment 1 lies in step 1), which is specifically:

[0117] The xanthan gum in step 1) was replaced with carboxymethyl cellulose (commercially available ACS grade, with a molecular weight distribution range of 1×10 3 -1×10 7 , polydispersity index is 4.33), after preliminary hydrolysis, dialysis, concentration, washing and drying, the molecular weight distribution range of the obtained carboxymethyl cellulose is 1×10 5 -1×10 6 , polydispersity index 1.35.

[0118] Preparation of a texturing additive composition: Add 97.98 parts of ultrapure water to 0.6 parts of the carboxymethyl cellulose obtained above, 0.4 parts of hematoxylin, 0.5 parts of 3-methyl-1,5-pentanediol, 0.4 parts of sodium benzoate, 0.1 parts of sodium lauryl sulfate, and 0.02 parts of maleic anhydride to obtain a texturing additive composition.

[0119] Figure 4 The SEM picture of the textured surface of the silicon wafer obtained in Example 4 is shown, indicating that by adjusting the content of the specific molecular weight and combining it with a suitable auxiliary nucleating agent and dispersant, a texturing additive with better texture uniformity can be obtained.

[0120] Example 5

[0121] The difference between this embodiment and embodiment 1 lies in step 1), which is specifically:

[0122] The xanthan gum in step 1) was replaced with sodium carboxymethyl starch (commercially available ACS grade, with a molecular weight distribution range of 1×10 3 -1×10 7 , polydispersity index is 2.01), after preliminary hydrolysis, dialysis, concentration, washing and drying, the molecular weight distribution range of the obtained sodium carboxymethyl starch is 1×10 3 -1×10 4 , polydispersity index 1.15.

[0123] Preparation of a texturing additive composition: Add 97.78 parts of ultrapure water to 0.6 parts of sodium carboxymethyl starch obtained as above, 0.1 parts of alkaline lignin, 1.0 parts of polyethylene glycol, 0.4 parts of sodium benzoate, 0.1 parts of sodium oleate, and 0.02 parts of maleic anhydride to obtain a texturing additive composition.

[0124] Figure 7 The SEM picture of the textured surface of the silicon wafer obtained in Example 5 is shown, indicating that by adjusting the molecular weight of the nucleating agent, a large-sized pyramid texture can be obtained, and the texture uniformity is excellent.

[0125] Example 6

[0126] The difference between this embodiment and embodiment 1 lies in step 1), which is specifically:

[0127] The xanthan gum in step 1) was replaced with carrageenan (commercially available ACS grade, with a molecular weight distribution range of 1×10 4 -1×10 7 , polydispersity index is 2.35), after preliminary hydrolysis, dialysis, concentration, washing and drying, the molecular weight distribution range of the obtained carrageenan is 1×10 4 -1×10 5 , polydispersity index 1.21.

[0128] Prepare a texturing additive composition: add 97.4 parts of ultrapure water to 1.0 part of the carrageenan obtained above, 0.6 part of sodium carbonate, 1.0 part of polypropylene glycol, 0.4 part of sodium citrate, and 0.2 part of sodium dodecylbenzenesulfonate to obtain a texturing additive composition.

[0129] Figure 8 The SEM picture of the textured surface of the silicon wafer obtained in Example 6 is shown, indicating that by adjusting the molecular weight of the nucleating agent, a medium-sized pyramid texture can be obtained, and the texture uniformity is excellent.

[0130] Example 7

[0131] The difference between this embodiment and embodiment 1 lies in step 1), which is specifically:

[0132] The xanthan gum in step 1) was replaced with sesbania gum (commercially available ACS grade, with a molecular weight distribution range of 1×10 3 -1×10 6 , polydispersity index is 2.35), after preliminary hydrolysis, dialysis, concentration, washing and drying, the molecular weight distribution range of the obtained sesbania gum is 1×10 5 -1×10 6 , polydispersity index 1.38.

[0133] Preparation of a texturing additive composition: Add 97.88 parts of ultrapure water to 0.3 parts of sesbania gum obtained above, 0.6 parts of sodium carbonate, 0.8 parts of chitosan oligosaccharide, 0.4 parts of sodium hexametaphosphate, and 0.02 parts of coconut oil monoethanolamide to obtain a texturing additive composition.

[0134] Figure 9 The SEM picture of the textured surface of the silicon wafer obtained in Example 7 is shown, indicating that by adjusting the molecular weight of the nucleating agent, a small-sized pyramid texture can be obtained, and the texture uniformity is excellent.

[0135] The average pile size (obtained using an electron microscope), reflectivity (obtained using a D8 reflectivity tester), and TOC value (obtained using a total organic carbon analyzer) of the comparative examples and examples above were measured. The results are shown in Table 1.

[0136] Table 1

[0137]

[0138] Results show that by adjusting the molecular weight of the nucleating agent, different pyramidal sizes can be achieved on the silicon wafer surface. The textured silicon wafers obtained with the preferred nucleating agent have advantages over currently preferred texturing additive compositions, including adjustable texture size, improved uniformity, and enhanced ability to remove organic contaminants from the silicon wafer surface.

[0139] The present application has been described above in conjunction with preferred embodiments, which are merely examples and serve as illustrations. On this basis, various combinations, replacements, and improvements may be made to the present application, all of which fall within the scope of protection of the present application.

Claims

1. A texturing additive composition for silicon wafers, comprising the following components: Nucleating agent 0.01-7.5 wt%; Etching control agent 0.05-5.5 wt%; Dispersant 0.0001-3.5 wt%; Surfactant 0.0-2.0 wt%; pH adjuster 0.0-5.0 wt%; water; in, The sum of the weight percentages of the components of the texturing additive composition is 100 wt %; The nucleating agent is a polysaccharide compound, the molecular weight distribution range of the polysaccharide compound is D1 to D2, and the polydispersity index is 1.00-1.90; wherein D2 and D1 are both within the range of 1×10 2 -1×10 7 Dalton, and D2:D1 is (5-50):1; The polysaccharide compound is selected from one or more of carboxymethyl cellulose, hydroxyethyl cellulose, sodium carboxymethyl starch, water-soluble starch, xanthan gum, carrageenan, locust bean gum, sesbania gum and carrageenan; The etching control agent is selected from polyethylene glycol, polypropylene glycol, polyethylene glycol monomethyl ether, polyethylene glycol dimethyl ether, polyethylene imine, polyvinyl alcohol, cyclohexanediol, 3-methyl-1,5-pentanediol, N - one or more of methylpyrrolidone, polyvinylpyrrolidone, chitosan, chitosan oligosaccharide and sorbitol; The dispersant is selected from one or more of sodium lactate, sodium benzoate, sodium tripolyphosphate, sodium hexametaphosphate, sodium 5-nitroguaiacol, sodium citrate, sodium gluconate, sodium methylene bisnaphthalene sulfonate, sodium carbonate, sodium acetate and sodium tartrate; The surfactant is selected from one or more of disodium lauryl sulfosuccinate, fatty alcohol polyoxyethylene ether, fatty acid methyl ester ethoxylate, fatty acid methyl ester ethoxylate sulfonate, disodium coconut monoethanolamide sulfosuccinate, sodium lauryl sulfate, sodium dodecylbenzenesulfonate and sodium oleate; The pH regulator is selected from one or more of sodium hydroxide, potassium hydroxide, propionic acid, acetic acid, formic acid, maleic acid, maleic anhydride, lauryl ether phosphate, cocoyl monoethanolamide, cocamidopropyl betaine and cocamidopropyl hydroxysulfonate.

2. The texturing additive composition according to claim 1, wherein D2:D1 is (5-20):

1.

3. The texturing additive composition according to claim 1, wherein The molecular weight distribution range of the polysaccharide compound is 1×10 3 -1×10 4 Dalton; or, The molecular weight distribution range of the polysaccharide compound is 1×10 4 -1×10 5 Dalton; or The molecular weight distribution range of the polysaccharide compound is 1×10 5 -1×10 6 Dalton; or The molecular weight distribution range of the polysaccharide compound is 1×10 6 -1×10 7 Dalton.

4. The texturing additive composition according to claim 1, wherein The polysaccharide compound is selected from one or more of sodium carboxymethyl starch, carrageenan, locust bean gum and xanthan gum.

5. The texturing additive composition according to claim 1, wherein The polysaccharide compound is prepared as follows: The polysaccharide raw material is hydrolyzed under acidic conditions, and then the molecular weight distribution range of the hydrolyzed polysaccharide raw material is narrowed to obtain the polysaccharide compound.

6. The texturing additive composition according to claim 5, wherein: The molecular weight distribution range is narrowed down to dialysis, and the dialysis comprises: The first dialysis was performed using a first dialysis bag with a molecular weight cut-off of D3, and the second dialysis was performed using a second dialysis bag with a molecular weight cut-off of D4.

7. The texturing additive composition according to claim 6, wherein: D3 is located at 1×10 2 -1×10 5 Between Dalton, D4 is located at 1×10 3 -1×10 6 Dalton between.

8. The texturing additive composition according to claim 1, wherein The texturing additive composition further includes an auxiliary nucleating agent in an amount of 0.00001-3.5 wt %, based on the total weight of the texturing additive composition.

9. The texturing additive composition according to claim 8, wherein The auxiliary nucleating agent is selected from one or more of sodium silicate, sodium chloride, potassium chloride, sodium carbonate, potassium carbonate, lignin and its derivatives, hematoxylin and its derivatives, and humic acid.

10. The texturing additive composition according to claim 1, wherein: The etching control agent is selected from one or more of polyethylene glycol monomethyl ether, 3-methyl-1,5-pentanediol, polyethyleneimine and chitosan oligosaccharide.

11. The texturing additive composition according to claim 1, wherein The dispersant is selected from one or more of sodium hexametaphosphate, sodium citrate and sodium benzoate.

12. The texturing additive composition according to claim 1, wherein The surfactant is selected from one or more of fatty alcohol polyoxyethylene ether, sodium lauryl sulfate and sodium dodecylbenzene sulfonate.

13. The texturing additive composition according to claim 1, wherein: The pH regulator is selected from one or more of sodium hydroxide, acetic acid and lauryl ether phosphate.

14. A texturing liquid comprising an alkali, the texturing additive composition according to any one of claims 1 to 13, and water.

15. The texturing liquid according to claim 14, wherein: The base is an inorganic base and / or an organic base.

16. The texturing liquid according to claim 15, wherein: The inorganic base is KOH and / or NaOH, and the organic base is tetramethylguanidine and / or tetraethylammonium hydroxide.

17. The texturing liquid according to claim 14, wherein The amount of the texturing additive composition is 0.05-1.5 wt %, based on the total weight of the texturing solution; The amount of the alkali is 0.5-5.5 wt %, based on the total weight of the texturing solution.

Images