Texturing additive composition for silicon wafer and texturing solution

Abstract

A texturing additive composition for a silicon wafer and a texturing solution. The texturing additive composition comprises the following components: 0.01-7.5 wt % of a nucleating agent; 0.05-5.5 wt % of an etching control agent; 0.0001-3.5 wt % of a dispersant; 0.0-2.0 wt % of a surfactant; 0.0-5.0 wt % of a pH regulator; and water. The texturing additive composition and the texturing solution meet the specific thin-film deposition requirements of heterojunction solar cells. The synergistic effect of the components in the texturing additive composition enables optimization of a textured surface structure combination while ensuring full surface texture coverage, thereby allowing for uniform distribution of textured surface pyramids, and lower apparent reflectance of the silicon wafer surface. The textured surface structure combination facilitates the subsequent amorphous silicon thin-film deposition process in heterojunction solar cells, while also exhibiting excellent light trapping properties.

Description

A texturing additive composition for silicon wafers and a texturing solution TECHNICAL FIELD

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

[0002] Heterojunction solar cells are a new type of high-efficiency solar cells, which were developed by introducing thin film deposition technology into crystalline silicon solar cells by Sanyo Company of Japan. Combined with IBC (Interdigitated Back Contact) technology, heterojunction solar cells have become one of the highest efficiency crystalline silicon cells, and have a broad development prospect. Thin film deposition technology is the key to guarantee the photoelectric conversion efficiency and stability of heterojunction solar cells. Based on the requirements of thin film deposition technology, the requirements for the texturing of single crystal silicon substrates of heterojunction solar cells are more stringent than those of traditional solar cells. Texturing the surface of single crystal silicon can not only reduce the reflectivity of the surface, but also make the light tilt into the cell to increase the optical path, thereby more effectively improving the photoelectric conversion efficiency of the cell.

[0003] Texturing is a process of using an alkali solution to anisotropically etch different crystal surfaces of single crystal silicon, thereby forming a pyramid textured surface on the silicon wafer. The uniformity of the pyramid textured surface on the surface of crystalline silicon and the size of the pyramid have a significant impact on the subsequent amorphous silicon thin film deposition process. Amorphous silicon thin film is difficult to uniformly deposit on the bottom of a too small pyramid; and due to the effect of stress, micro-cracks are easily generated, resulting in poor passivation effect. Therefore, increasing the size of the pyramid can effectively improve the open-circuit voltage of the silicon heterojunction solar cell, and good pyramid uniformity can improve the light trapping property to improve the short-circuit current of the solar cell, thereby improving the photoelectric conversion efficiency of the silicon heterojunction solar cell. In addition, due to the difference in the film plating process adopted by different solar cell manufacturers, the size of the pyramid textured surface corresponding to different film plating processes is quite different to obtain the best effect.

[0004] The existing texturing solution cannot simultaneously consider the uniformity of the textured surface and the regulation of different pyramid sizes. Therefore, it is very important for the development of silicon heterojunction solar cells to develop a new type of texturing additive composition to achieve the purpose of adjustable pyramid size of the textured surface and good uniformity of the textured surface.

[0005] SUMMARY

[0006] The present application provides a texturing additive composition for silicon wafers, comprising the following components:

[0007] wherein the sum of the weight percentages of the components of the additive composition is 100 wt.%;

[0008] The nucleating agent is a polysaccharide compound having a molecular weight distribution range of D1 to D2 and a polydispersity index of 1.00-1.90; wherein D2 and D1 are both located in the range of 1 x 10 2 -1 x 10 7 Daltons, and D2:D1 is (5-50):1, preferably (5-20):1.

[0009] In one embodiment, the polysaccharide compound has a molecular weight distribution range of 1 x 10 3 -1 x 10 4 Daltons; or,

[0010] the polysaccharide compound has a molecular weight distribution range of 1 x 10 4 -1 x 10 5 Daltons; or

[0011] the polysaccharide compound has a molecular weight distribution range of 1 x 10 5 -1 x 10 6 Daltons; or

[0012] the polysaccharide compound has a molecular weight distribution range of 1 x 10 6 -1 x 10 7 Daltons.

[0013] 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, sorgo gum, and carrageenan.

[0014] Preferably, the polysaccharide compound is selected from one or more of sodium carboxymethyl starch, carrageenan, locust bean gum, and xanthan gum.

[0015] In one embodiment, the polysaccharide compound is prepared as follows:

[0016] The polysaccharide raw material is hydrolyzed under acidic conditions, and then the hydrolyzed polysaccharide raw material is subjected to a molecular weight distribution range reduction to obtain the polysaccharide compound.

[0017] In one embodiment, the molecular weight distribution range reduction is dialysis, and the dialysis comprises:

[0018] a first dialysis with a first dialysis bag having a molecular weight cut-off of D1 and a second dialysis with a second dialysis bag having a molecular weight cut-off of D2.

[0019] In one embodiment, D1 is located in the range of 1 x 102 -1 x 10 5 D2 is located between 1 x 10 3 -1 x 10 6 Daltons.

[0020] In an 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.

[0021] In an 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.

[0022] In an embodiment, the etching control agent is selected from one or more of polyethylene glycol, polypropylene glycol, polyethylene glycol monomethyl ether, polyethylene glycol dimethyl ether, polyethylene imine, polyvinyl alcohol, cyclohexanediol, 3-methyl-1,5-pentanediol, N-methylpyrrolidone, polyvinylpyrrolidone, chitosan, chitooligosaccharide, and sorbitol; preferably, the etching control agent is selected from one or more of polyethylene glycol monomethyl ether, 3-methyl-1,5-pentanediol, polyethylene imine, and chitooligosaccharide.

[0023] In an embodiment, the dispersant is selected from one or more of sodium lactate, sodium benzoate, sodium tripolyphosphate, sodium hexametaphosphate, sodium 5-nitrosalicylate, sodium citrate, sodium gluconate, sodium methylene bis-naphthalene 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.

[0024] In an 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, sodium cocoyl monoethanolamide sulfosuccinate, sodium dodecyl sulfate, sodium dodecyl benzene sulfonate, and sodium oleate; preferably, the surfactant is selected from one or more of fatty alcohol polyoxyethylene ether, sodium dodecyl sulfate, and sodium dodecyl benzene sulfonate.

[0025] In an 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 hydroxysultaine; preferably, the pH adjuster is selected from one or more of sodium hydroxide, acetic acid, and lauryl ether phosphate.

[0026] The present application also provides a texturing solution comprising a base, the texturing additive composition of the present application, and water.

[0027] In an 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.

[0028] In an embodiment, the amount of the texturing additive composition is 0.05-1.5 wt% based on the total weight of the texturing solution.

[0029] The amount of the base is 0.5-5.5 wt% based on the total weight of the texturing solution.

[0030] The texturing additive composition and the texturing solution of the present application can match the special thin film deposition requirement of the heterojunction solar cell. 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 textured surface pyramid is uniformly distributed, the uniformity of the textured surface is good, and the apparent reflectivity of the silicon wafer surface is lower. This 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 at the same time has excellent light trapping property, so as to obtain a stable and reliable heterojunction solar cell. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 shows the SEM picture of the textured surface of the silicon wafer obtained in Example 1 after texturing;

[0032] Figure 2 shows the SEM picture of the textured surface of the silicon wafer obtained in Example 2 after texturing;

[0033] Figure 3 shows the SEM picture of the textured surface of the silicon wafer obtained in Example 3 after texturing;

[0034] Figure 4 shows the SEM picture of the textured surface of the silicon wafer obtained in Example 4 after texturing;

[0035] Figure 5 shows the SEM picture of the textured surface of the silicon wafer obtained in Comparative Example 1 after texturing;

[0036] Figure 6 shows the SEM picture of the textured surface of the silicon wafer obtained in Comparative Example 2 after texturing;

[0037] Figure 7 shows the SEM picture of the textured surface of the silicon wafer obtained in Example 5 after texturing;

[0038] Figure 8 shows the SEM picture of the textured surface of the silicon wafer obtained in Example 6 after texturing;

[0039] Figure 9 shows the SEM picture of the textured surface of the silicon wafer obtained in Example 7 after texturing;

[0040] Figure 10 shows the molecular weight distribution curve of the xanthan gum in Comparative Example 1;

[0041] Figure 11 shows the molecular weight distribution curve of the xanthan gum obtained by preliminary hydrolysis in Comparative Example 2;

[0042] Figure 12 shows the molecular weight distribution curve of the xanthan gum obtained in Example 1. DETAILED DESCRIPTION

[0043] The application will be further described by the following drawings and examples. The features and advantages of the application will become more apparent from the description.

[0044] The term "exemplary" is used herein to mean "serving as an example, instance, or illustration." Any implementation described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other implementations. Unless specifically indicated otherwise, the drawings shown in the Figures are not necessarily to scale.

[0045] Furthermore, the technical features involved in the different embodiments of the application described below can be combined with each other as long as there is no conflict.

[0046] The application provides a texturing additive composition for silicon wafer, comprising the following components:

[0047] wherein the sum of the weight percentages of the components of the texturing additive composition is 100wt%;

[0048] 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 between 1x10 2 -1x10 7 Daltons, and D2:D1 is (5-50):1, preferably (5-20):1.

[0049] In the 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 less than D1 is less than 10%, even less than 5%, even less than 1% of the total mass percentage of all molecules; the total mass percentage of molecules with a molecular weight greater than D2 is also less than 10%, even less than 5%, even less than 1% of the total mass percentage of all molecules. That is, the total mass percentage of molecules with a molecular weight between D1 and D2 is more than 85%, even more than 90%, even more than 95% of the total mass percentage of all molecules.

[0050] The polysaccharide compound used in the present application has a narrow molecular weight distribution (polydispersity index) and a relatively small range of molecular weight distribution. The inventors of the present application unexpectedly found that when a single crystal silicon wafer is texturized using a texturing solution containing such a polysaccharide compound having a relatively narrow range of molecular weight distribution as a nucleating agent, a pyramid texture having very good uniformity can be obtained. Furthermore, by adjusting the values of D1 and D2 in the range of molecular weight distribution, the size of the pyramid texture can also be adjusted, i.e. when D1 and D2 are relatively large, a pyramid texture having a relatively small size is obtained; when D1 and D2 are relatively small, a pyramid texture having a relatively large size can be obtained. Thus, according to different requirements, the upper and lower limits of the range of molecular weight distribution can be selected.

[0051] In one embodiment, the polysaccharide compound has a range of molecular weight distribution of 1 x 10 3 -1 x 10 4 ; or the polysaccharide compound has a range of molecular weight distribution of 1 x 10 4 -1 x 10 5 ; or the polysaccharide compound has a range of molecular weight distribution of 1 x 10 5 -1 x 10 6 ; or the polysaccharide compound has a range of molecular weight distribution of 1 x 10 6 -1 x 10 7 . Within this range of molecular weight distribution, the polysaccharide compound has a unimodal molecular weight distribution curve and a relatively narrow polydispersity index PDI of 1.00-1.90, for example 1.05-1.70, for example 1.10-1.60.

[0052] The nucleating agent is a polysaccharide compound having a specific range of molecular weight distribution and molecular weight distribution, which has the structural feature of being a high molecular weight compound having multiple hydroxyl groups. During the texturing process, the hydroxyl groups are adsorbed on the surface of the silicon wafer, which can hinder the reaction between OH - ions in the alkaline solution and the silicon wafer, thereby forming a texturing point at the adsorption site.

[0053] 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 furcelleran.

[0054] Preferably, the polysaccharide compound is selected from one or more of sodium carboxymethyl starch, carrageenan, locust bean gum and xanthan gum.

[0055] In one embodiment, the polysaccharide compound used in the present application can be prepared as follows:

[0056] The polysaccharide raw material is hydrolyzed under acidic conditions, and then the hydrolyzed polysaccharide raw material is subjected to a molecular weight distribution range reduction to obtain the polysaccharide compound.

[0057] The polysaccharide raw materials used in the present application are all commercially available USP or ACS grade. After the applicant purchased the polysaccharide raw material, the molecular weight distribution was determined, and the molecular weight distribution range of the polysaccharide raw material was ensured to be not less than 1 x 10 7 Daltons, so as to ensure that the polysaccharide compound can be prepared by the above method.

[0058] The preliminary hydrolysis process can be carried out as follows: the nucleating agent raw material (polysaccharide compound raw material) is completely dissolved in a strong inorganic acid such as a strong inorganic acid (for example, hydrochloric acid, sulfuric acid, etc.) with a concentration of 0.01-1.0 mol / L, and heated at a certain temperature (for example, 50-80°C) for a period of time (for example, 1-24 h) to carry out preliminary hydrolysis, and then the solution is adjusted to neutral pH with a base such as NaOH solution or KOH solution after hydrolysis.

[0059] After preliminary hydrolysis, the molecular weight distribution range is reduced to obtain the polysaccharide compound used as a nucleating agent in the present application. The molecular weight distribution range reduction can be carried out by separation means such as extraction, column chromatography, electrophoresis, centrifugation, and recrystallization. Dialysis can be carried out in one dialysis process, and the solution retained in the dialysis bag after dialysis is the polysaccharide compound used as a nucleating agent in the present application.

[0060] Two dialysis processes can also be carried out: the first dialysis is carried out with a first dialysis bag with a retention molecular weight of D1, and the second dialysis is carried out with a second dialysis bag with a retention molecular weight of D2. It should be noted that the order of the first dialysis with the first dialysis bag with a retention molecular weight of D1 and the second dialysis with the second dialysis bag with a retention molecular weight of D2 can be changed. That is, the first dialysis can be carried out with the first dialysis bag with a retention molecular weight of D1 first, and then the solution in the first dialysis bag is transferred to the second dialysis bag with a retention molecular weight of D2 for the second dialysis. The dialysis can also be carried out with the second dialysis bag with a retention molecular weight of D2 first, and then the solution outside the second dialysis bag is transferred to the first dialysis bag with a retention molecular weight of D1 for dialysis.

[0061] In one embodiment, D1 is between 1 x 10 2 -1 x 10 5 Daltons, and D2 is between 1 x 10 3 -1 x 10 6 Daltons.

[0062] In the texturing additive composition of the present application, the amount of the above-mentioned nucleating agent is 0.01-7.5 wt%, for example, 0.1-5.0 wt%, for example, 0.2-4.0 wt%, based on the total weight of the texturing additive composition.

[0063] In one embodiment, the texturing additive composition further comprises 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 role of the auxiliary nucleating agent is to help the nucleating agent to be more uniformly distributed on the surface of the silicon wafer, and to increase the nucleation rate.

[0064] In one embodiment, the etching control agent is selected from one or more of polyethylene glycol, polypropylene glycol, polyethylene glycol monomethyl ether, polyethylene glycol dimethyl ether, polyethylene imine, polyvinyl alcohol, cyclohexanediol, 3-methyl-1,5-pentanediol, N-methylpyrrolidone, polyvinylpyrrolidone, chitosan, chitooligosaccharide, and sorbitol; preferably, the etching control agent is selected from one or more of polyethylene glycol monomethyl ether, 3-methyl-1,5-pentanediol, polyethylene imine, and chitooligosaccharide. The role of the etching control agent is to adjust the etching rate of the alkaline solution on the silicon wafer, and to help the anisotropic etching of the single crystal silicon wafer to obtain the pyramidal texture. In the texturing additive composition of the present application, the amount of the etching control agent is 0.05-5.5 wt%, for example, 0.1-5.0 wt%, for example 0.2-2.0 wt%; based on the total weight of the texturing additive composition.

[0065] In one embodiment, the dispersing agent is selected from one or more of sodium lactate, sodium benzoate, sodium tripolyphosphate, sodium hexametaphosphate, sodium 5-nitrosalicylate, sodium citrate, sodium gluconate, sodium methylene bis-naphthalene sulfonate, sodium carbonate, sodium acetate, and sodium tartrate; preferably, the dispersing agent 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 dispersing agent 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.

[0066] In one embodiment, the texturing additive composition of the present application can further contain a surfactant. 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, sodium cocoyl monoethanolamide sulfosuccinate, sodium dodecyl sulfate, sodium dodecyl benzene sulfonate, and sodium oleate; preferably, the surfactant is selected from one or more of fatty alcohol polyoxyethylene ether, sodium dodecyl sulfate, and sodium dodecyl benzene sulfonate. In the texturing additive composition of the present application, the amount of 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.

[0067] In one embodiment, the texturing additive composition of the present application can further contain a pH adjuster. 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 hydroxysultaine; preferably, the pH adjuster 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 pH adjuster 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.

[0068] As mentioned before, the existing texturing technology cannot meet the needs of the cleaning and texturing of heterojunction solar cells. Specifically, first, the pyramids of the solar cell texturing surface obtained by using the conventional texturing additive composition of silicon wafer have small size and poor uniformity (the size of the pyramids is generally 0.8-2 μm, and the average size is less than 1.5 μm), which is not conducive to the deposition of amorphous silicon film, thereby affecting the photoelectric conversion efficiency and stability of the heterojunction solar cell; and it is difficult to simultaneously consider the uniformity of the texturing surface and the regulation of different pyramid sizes. Second, the existing texturing process has a long etching time, such as the texturing time of more than 750 s in patent CN102330155A, which is not conducive to the improvement of production efficiency and cannot meet the needs of the production and development of silicon heterojunction solar cells. Third, the texturing solution using the conventional texturing additive composition has strong adsorption to the surface of the silicon wafer, and the TOC value (Total Organic Carbon) of the surface of the silicon wafer is high after the texturing is completed, which will reduce the photoelectric conversion efficiency of the solar cell and affect its stability and reliability.

[0069] The texturing additive composition and the texturing solution of the present application can match the special thin film deposition requirement of the heterojunction solar cell. The synergistic effect of the components of the texturing additive composition realizes the optimization of the structure combination of the texturing surface on the basis of ensuring the texturing coverage rate, so that the pyramid distribution is uniform, the texturing surface uniformity is good, and the apparent reflectivity of the silicon wafer surface is lower. This structure combination of the texturing surface is beneficial to the deposition of amorphous silicon thin film in the next process of the heterojunction solar cell, and meanwhile has excellent light trapping property, so that a stable and reliable heterojunction solar cell is obtained.

[0070] The pyramid size during texturing can be controlled by adjusting the different molecular weight distribution range of the nucleating agent, so that small, medium and large size pyramids are obtained. The average size of the small size pyramid is about 1.4 μm, the average size of the medium size pyramid is about 2.3 μm, and the average size of the large size pyramid is 3.2 μm. Different pyramid texturing sizes can match different solar cell film coating processes, and the application range of the texturing additive composition is enhanced.

[0071] The water solubility of each component of the texturing additive composition of the present application is high, and meanwhile the adsorption of each component to the surface of the silicon wafer is low, so that each component of the additive composition is easy to clean, and the TOC value of the silicon wafer surface after the cleaning step is reduced.

[0072] The texturing solution containing the texturing additive composition of the present application applied to texturing requires a texturing time of less than 500 s at 75-82 ℃, and the shortest time can be 400 s, while the texturing time required by the existing heterojunction solar cell texturing solution is more than 500 s on average. The application of the texturing additive composition can reduce the texturing time, improve the production efficiency, and further reduce the production cost of the heterojunction solar cell.

[0073] The present application also provides a texturing solution containing a base, the texturing additive composition of the present application and water.

[0074] In an 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 tetramethyl guanidine and / or tetraethyl ammonium hydroxide.

[0075] In an embodiment, the amount of the texturing additive composition is 0.05-1.5 wt%, based on the total weight of the texturing solution.

[0076] The amount of the base is 0.5-5.5 wt%, based on the total weight of the texturing solution.

[0077] The texturing solution can be prepared as follows: in a texturing tank, a certain mass of inorganic / organic base is dissolved in ultrapure water to prepare a base 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 base solution, the content of the texturing additive composition being 0.15-1.5 wt% (based on the total weight of the texturing solution), and the mixture is stirred uniformly to obtain the texturing solution.

[0078] In the present application, the above-mentioned silicon wafer can be N-type monocrystalline silicon or P-type monocrystalline silicon, etc.

[0079] Comparative Example 1

[0080] Texturing of a monocrystalline silicon wafer is carried out by the following process steps:

[0081] 1) Preparation of the texturing additive composition: 1.5 parts of xanthan gum raw material (commercially available USP grade, after purchase, the molecular weight distribution range is 1 x 10 4 -1 x 10 7 , the molecules with a molecular weight lower than 10 4 account for 1% of the total mass of all molecules, and the molecules with a molecular weight higher than 10 7 account for 0.1% of the total mass of all molecules, and the molecular weight distribution curve is shown in FIG. 10; the number average molecular weight is 162395; the 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-nitrosodium guaiacol, 0.2 parts of sodium dodecyl sulfate, 0.05 parts of sodium hydroxide, and 96.85 parts of ultrapure water are added to obtain the texturing additive composition.

[0082] 2) Preparation of the texturing solution: 100 parts of KOH is dissolved in 6900 parts of ultrapure water to obtain a base solution; 28 parts of the texturing additive composition prepared in step 1) is added to the base solution to obtain the texturing solution.

[0083] 3) Texturing of the silicon wafer: the clean silicon wafer is placed in the texturing solution prepared in step 2) heated to 82°C for etching for 480 s.

[0084] 4) Cleaning of the silicon wafer: the silicon wafer after texturing in step 3) is cleaned with deionized water, and the deionized water on the surface of the silicon wafer after cleaning is blown dry with high-purity nitrogen.

[0085] FIG. 5 shows the SEM picture of the textured surface of the silicon wafer obtained in Comparative Example 1, and the textured surface is not fully covered and cannot be completely textured.

[0086] Comparative Example 2

[0087] The difference between the present comparative example and Comparative Example 1 is in step 1), which is as follows:

[0088] The xanthan gum raw material in Comparative Example 1 was pretreated, i.e. the xanthan gum was completely dissolved in 0.05 mol / L HCl solution, heated at 80°C for 6 h for preliminary hydrolysis, after the hydrolysis was completed, NaOH was added to adjust the solution to neutral, to obtain a preliminary hydrolysis xanthan gum solution, which was concentrated, washed and dried to obtain the preliminary hydrolysis xanthan gum (the molecular weight distribution range of the obtained xanthan gum was 1 x 10 3 -1 x 10 7 , the molecules with a molecular weight lower than 10 3 accounted for 3% of the total mass of all molecules, the molecules with a molecular weight higher than 10 7 accounted for 0.1% of the total mass of all molecules, and the molecular weight distribution curve is shown in Figure 11; the polydispersity index was 4.05.

[0089] The texturing additive composition was prepared: 1.5 parts of the preliminary hydrolysis xanthan gum, 0.1 part of humic acid, 1.0 part of polyethylene glycol monomethyl ether, 0.3 part of 5-nitrosodium guaiacol, 0.2 part of sodium dodecyl sulfate, 0.05 part of sodium hydroxide, and 96.85 parts of ultrapure water were added to obtain the texturing additive composition.

[0090] Figure 6 shows the SEM image of the silicon wafer after texturing of the silicon wafer obtained in Comparative Example 2, and the size distribution of the pyramids is uneven, and the uniformity of the surface is very poor.

[0091] Example 1

[0092] The difference between this example 1 and Comparative Example 2 is in step 1), which is as follows:

[0093] The preliminary hydrolysis xanthan gum solution in Comparative Example 2 was dialyzed, i.e. the preliminary hydrolysis xanthan gum solution was placed in a first dialysis bag with a molecular weight cut-off of 1 x 10 5 Daltons, and was placed in a beaker containing 1.5 L of ultrapure water for dialysis separation, after the dialysis was completed, the solution in the first dialysis bag was transferred to a second dialysis bag with a molecular weight cut-off of 1 x 10 6 Daltons, and was placed in a beaker containing 1.5 L of ultrapure water for secondary dialysis separation, and after completion, the dialysate was concentrated, washed and dried to obtain the xanthan gum which can be used as a nucleating agent in this example (the molecular weight distribution range of the obtained xanthan gum was 1 x 10 5 -1 x 10 6 , the molecules with a molecular weight lower than 10 5 accounted for 1% of the total mass of all molecules, the molecules with a molecular weight higher than 10 6 accounted for 3% of the total mass of all molecules, and the molecular weight distribution curve is shown in Figure 12; the polydispersity index PDI was 1.31.

[0094] A texturing additive composition was prepared: 1.5 parts of the xanthan gum obtained above, 0.1 parts of humic acid, 1.0 parts of polyethylene glycol monomethyl ether, 0.3 parts of 5-nitrosodium guaiacol, 0.2 parts of sodium dodecyl sulfate, 0.05 parts of sodium hydroxide, were added to 96.85 parts of ultrapure water to obtain the texturing additive composition.

[0095] Figure 1 shows the SEM picture of the textured surface of the silicon wafer obtained in Example 1. Compared with Comparative Example 1, the average pyramid size is larger, the uniformity of the textured surface is better, the reflectivity is lower, and the TOC value is lower than that of Comparative Example 1.

[0096] Example 2

[0097] The difference between this example and Example 1 is in step 1), which is specifically:

[0098] The first dialysis bag in step 1) has a molecular weight cut-off of 1 x 10 4 Daltons, and the second dialysis bag has a molecular weight cut-off of 1 x 10 5 Daltons. The molecular weight distribution range of the obtained xanthan gum is 1 x 10 4 -1 x 10 5 Daltons, and the polydispersity index is 1.22.

[0099] Figure 2 shows the SEM picture of the textured surface of the silicon wafer obtained in Example 2, which shows that by adjusting the molecular mass of the nucleating agent, a large-size pyramid textured surface can be obtained, and the uniformity of the textured surface is better.

[0100] Example 3

[0101] The difference between this example and Example 1 is in step 1), which is specifically:

[0102] In step 1), only one dialysis is performed using a dialysis bag with a molecular weight cut-off of 1 x 10 6 Daltons. The molecular weight distribution range of the obtained xanthan gum is 1 x 10 6 -1 x 10 7 Daltons, and the polydispersity index is 1.26.

[0103] Figure 3 shows the SEM picture of the textured surface of the silicon wafer obtained in Example 3, which shows that by adjusting the molecular mass of the nucleating agent, a small-size pyramid textured surface can be obtained, and the uniformity of the textured surface is better.

[0104] Example 4

[0105] The difference between this example and Example 1 is in step 1), which is specifically:

[0106] In step 1), the xanthan gum raw material is replaced by a carboxymethyl cellulose raw material (commercially available ACS grade, which is tested after purchase to have a molecular weight distribution range of 1 x 10 3 -1 x 107 , the molecular weight distribution range of the carboxymethyl cellulose obtained after preliminary hydrolysis, dialysis, concentration, washing, drying is 1 x 107 5 - 1 x 107 6 , and the polydispersity index is 1.35.

[0107] The texturing additive composition was prepared: 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 dodecyl sulfate, 0.02 parts of maleic anhydride, and 97.98 parts of ultrapure water were added to obtain the texturing additive composition.

[0108] Figure 4 shows the SEM picture of the silicon wafer after texturing, indicating that by adjusting the content of the specific molecular mass, and simultaneously matching the appropriate auxiliary nucleating agent and dispersant, a texturing additive with better uniformity of the textured surface can be obtained.

[0109] Example 5

[0110] The difference between this example and Example 1 is in step 1), specifically:

[0111] The xanthan gum raw material in step 1) was replaced by sodium carboxymethyl starch raw material (commercially available ACS grade, and the molecular weight distribution range was 1 x 107 3 - 1 x 107 7 , and the polydispersity index is 2.01), and after preliminary hydrolysis, dialysis, concentration, washing, drying, the molecular weight distribution range of the sodium carboxymethyl starch obtained was 1 x 107 3 - 1 x 107 4 , and the polydispersity index is 1.15.

[0112] The texturing additive composition was prepared: 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 dodecyl sulfate, 0.02 parts of maleic anhydride, and 97.98 parts of ultrapure water were added to obtain the texturing additive composition.

[0113] Figure 7 shows the SEM picture of the silicon wafer after texturing, indicating that by adjusting the molecular mass of the nucleating agent, a large size pyramid textured surface can be obtained, and the uniformity of the textured surface is excellent.

[0114] Example 6

[0115] The difference between this example and Example 1 is in step 1), specifically:

[0116] The xanthan gum raw material in step 1) was replaced by carrageenan raw material (commercially available ACS grade, and the molecular weight distribution range was 1 x 107 4-1×10 7 With a polydispersity index of 2.35, after preliminary hydrolysis, dialysis, concentration, washing, and drying, the molecular weight distribution range of the obtained carrageenan is 1×10⁻⁶. 4 -1×10 5 The polydispersity index is 1.21.

[0117] Preparation of the texturing additive composition: 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 were added to 97.4 parts of ultrapure water to obtain the texturing additive composition.

[0118] Figure 8 shows a SEM image of the textured surface of the silicon wafer obtained in Example 6, indicating that by adjusting the molecular weight of the nucleating agent, a medium-sized pyramid textured surface can be obtained, while the textured surface has excellent uniformity.

[0119] Example 7

[0120] The difference between this embodiment and Embodiment 1 lies in step 1), which is as follows:

[0121] Replace the xanthan gum raw material in step 1) with guar gum raw material (commercially available ACS grade, with a molecular weight distribution range of 1×10⁻⁶ after purchase and testing). 3 -1×10 6 (With a polydispersity index of 2.35), after preliminary hydrolysis, dialysis, concentration, washing, and drying, the molecular weight distribution range of the obtained guar gum was 1×10⁻⁶. 5 -1×10 6 The polydispersity index is 1.38.

[0122] Preparation of the texturing additive composition: 0.3 parts of the guar gum obtained above, 0.6 parts of sodium carbonate, 0.8 parts of chitosan oligosaccharide, 0.4 parts of sodium hexametaphosphate, 0.02 parts of cocoyl monoethanolamide, and 97.88 parts of ultrapure water were added to obtain the texturing additive composition.

[0123] Figure 9 shows a SEM image of the textured surface of the silicon wafer obtained in Example 7, indicating that by adjusting the molecular weight of the nucleating agent, a small-sized pyramid textured surface can be obtained, while the textured surface has excellent uniformity.

[0124] The average velour size (obtained using electron microscopy), reflectance (obtained using a D8 reflectometer), and TOC value (obtained using a total organic carbon analyzer) of the above comparative examples and embodiments were measured. The results are shown in Table 1.

[0125] Table 1

[0126] The results show that by adjusting the molecular weight of the nucleating agent, different pyramid sizes of the textured surface can be obtained on the silicon wafer. The preferred nucleating agent has the advantages of adjustable textured surface size, good uniformity, and stronger ability to remove organic contaminants on the silicon wafer surface compared to the current preferred additive composition for texturing.

[0127] The above describes the present application in combination with the preferred embodiments, which are only examples and serve as illustrations. On this basis, various combinations, substitutions and improvements can be made to the present application, which all fall within the protection scope of the present application.

Claims

1. A texturizing additive composition for silicon wafers comprising the following components: wherein The sum of the weight percentages of the components of the texturing additive composition is 100 wt%; The nucleating agent is a polysaccharide compound with a molecular weight distribution range of D1 to D2 and a polydispersity index of 1.00-1.90; wherein D2 and D1 are both between 1 x 10 2 and 1 x 10 7 Daltons, and D2:D1 is (5-50):1, preferably (5-20):

1.

2. The etching additive composition of claim 1, wherein, The molecular weight distribution range of the polysaccharide compound is 1 x 10 3 -1 x 10 4 Daltons; Alternatively, The molecular weight distribution range of the polysaccharide compound is 1 x 10 4 -1 x 10 5 Daltons; Alternatively The molecular weight distribution range of the polysaccharide compound is 1 x 10 5 -1 x 10 6 Daltons; Alternatively The molecular weight distribution range of the polysaccharide compound is 1 x 10 6 -1 x 10 7 Daltons.

3. The etching additive composition of claim 1, wherein, 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, mesquite gum, and carraghenan. Preferably, the polysaccharide compound is selected from one or more of sodium carboxymethyl starch, carrageenan, locust bean gum, and xanthan gum.

4. The etching additive composition of claim 1, wherein, The polysaccharide compound is prepared by: The polysaccharide raw material is hydrolyzed under acidic conditions, and then the hydrolyzed polysaccharide raw material is subjected to a molecular weight distribution range reduction to obtain the polysaccharide compound.

5. The etching additive composition of claim 4, wherein, The molecular weight distribution range reduction is dialysis, which includes: The first dialysis is performed using a first dialysis bag having a molecular weight cut-off of D1, and the second dialysis is performed using a second dialysis bag having a molecular weight cut-off of D2.

6. The etching additive composition of claim 5, wherein, D1 is located between 1 x 10 2 -1 x 10 5 D2 is located between 1 x 10 3 -1 x 10 6 Daltons.

7. The etching additive composition of 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.

8. The etching additive composition of claim 7, wherein, The auxiliary nucleating agent is selected from one or more of sodium silicate, sodium chloride, potassium chloride, sodium carbonate, potassium carbonate, lignin and derivatives thereof, hematoxylin and derivatives thereof, and humic acid and extracts thereof.

9. The etching additive composition of claim 1, wherein, The etching control agent is selected from one or more of polyethylene glycol, polypropylene glycol, polyethylene glycol monomethyl ether, polyethylene glycol dimethyl ether, polyethylene imine, polyvinyl alcohol, cyclohexanediol, 3-methyl-1,5-pentanediol, N-methylpyrrolidone, polyvinylpyrrolidone, chitosan, chitooligosaccharide, and sorbitol; preferably, the etching control agent is selected from one or more of polyethylene glycol monomethyl ether, 3-methyl-1,5-pentanediol, polyethylene imine, and chitooligosaccharide.

10. The etching additive composition of claim 1, wherein, The dispersant is selected from one or more of sodium lactate, sodium benzoate, sodium tripolyphosphate, sodium hexametaphosphate, sodium 5-nitrosalicylate, sodium citrate, sodium gluconate, sodium methylene bis-naphthalene 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.

11. The etching additive composition of claim 1, wherein, 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, sodium cocoyl monoethanolamide sulfosuccinate, sodium dodecyl sulfate, sodium dodecylbenzenesulfonate, and sodium oleate; preferably, the surfactant is selected from one or more of fatty alcohol polyoxyethylene ether, sodium dodecyl sulfate, and sodium dodecylbenzenesulfonate.

12. The etching additive composition of claim 1, wherein, 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, sodium cocoyl monoethanolamide, cocamidopropyl betaine, and cocamidopropyl hydroxysultaine; preferably, the pH adjuster is selected from one or more of sodium hydroxide, acetic acid, and lauryl ether phosphate.

13. A texturing solution comprising an alkali, the texturing additive composition of any one of claims 1-12, and water.

14. The etching liquid according to claim 13, wherein, 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.

15. The etching liquid of claim 13, 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 base is 0.5-5.5 wt%, based on the total weight of the texturing solution.

Images