Monocrystalline silicon texturing additive having strong stain-cleaning capability, and texturing method

Abstract

Disclosed in the present invention are a monocrystalline silicon wafer texturing additive having strong stain-cleaning capability, and a texturing method. The additive comprises the following raw material components by weight percentage: 0.8-2 parts of natural macromolecular sugars, 0.05-0.5 parts of surface texture regulator, 0.5-2 parts of cleaning aid, 0.05-0.2 parts of surfactant, 1.0 part of inorganic base, and 94.3-100 parts of deionized water. Also disclosed are a method for preparing the texturing additive, and a use thereof. The texturing additive of the present invention has a good cleaning effect on incoming wafers which have severe contamination. During a texturing process, a textured surface effect can be achieved in one step without the need for a coarse polishing process, effectively reducing process steps and chemical consumption.

Description

[Corrected according to Rule 26 14.09.2024] A single crystal silicon texturing additive with strong contamination cleaning ability and a texturing method TECHNICAL FIELD

[0001] The utility model relates to a single crystal silicon texturing additive with strong contamination cleaning ability and a texturing method, and belongs to the technical field of photovoltaic single crystal silicon cell manufacturing. BACKGROUND

[0002] Single crystal silicon texturing technology is an important step in the production process of solar cell, and is closely related to the development of solar cell. The working principle of solar cell is based on the absorption of light and the generation of electron-hole pairs, and then the current is generated.

[0003] The main purpose of the texturing technology is to manufacture microstructure on the surface of single crystal silicon by alkali solution, so as to reduce the reflection of light and improve the absorption rate of light. Specifically, the texturing technology can form a series of small pyramid or inverted pyramid structures on the surface of the silicon wafer, which has high roughness and specific surface area, effectively increases the contact area of light, makes more light enter the silicon body to interact, enhances the excitation of photo-generated carriers, and thus improves the short-circuit current and the efficiency of the cell.

[0004] The preparation process of single crystal silicon cell includes texturing, diffusion, etching, coating, silk printing and other processes; among them, the diffusion process is the most core step of preparing P-N junction of solar cell, which is greatly affected by process conditions and previous texturing process; because the cutting liquid and the silicon wafer directly contact with the adhesive stick during the cutting process, there are organic residues and some metal impurities on the surface of the silicon wafer, mainly including C, O, Ca, F and other elements, if not cleaned thoroughly, it will bring a series of adverse effects on the preparation of P-N junction when entering the high temperature furnace tube. In addition to the contamination after the cutting of the silicon wafer, the residual texturing liquid, particles or organic matter will also cause uneven distribution of the diffusion source on the surface of the silicon wafer, affect the diffusion depth, and increase the contact resistance of the cell by the covering on the surface, thus reducing the fill factor, and affecting the subsequent process and the performance of the cell; moreover, the particles or impurities not cleaned thoroughly may cause defects on the surface of the silicon wafer, uneven texturing, white spots, and other phenomena, resulting in local short circuit or open circuit, reducing the effective area and minority carrier lifetime of the cell, causing EL failure, and reducing the efficiency and yield of the cell.

[0005] For incoming material pollution serious single crystal silicon raw silicon wafer, including organic matter residue, positive and negative pieces, edge color difference and appearance, which may affect the reaction of etching liquid and the surface of silicon wafer; although part of the production line is usually rough polishing pretreatment for this kind of piece source, in order to achieve surface cleaning and mechanical damage layer treatment, but improper treatment, still leave residues or cause new damage on the surface of silicon wafer, which will have adverse effects on the subsequent etching and cell manufacturing process.

[0006] In addition to the rough polishing process, for the single crystal silicon wafer with heavy surface pollution, the surface organic matter and part of the metal ion in the production line process is mainly relied on hydrogen peroxide and alkali solution to decompose the surface organic matter, for the production line, a large amount of hydrogen peroxide consumption will inevitably bring cost burden, by preparing the etching additive with strong cleaning ability, the surface dirt can be removed, and the additive itself on the silicon wafer can be reduced, at the same time, the dependence on hydrogen peroxide can be reduced to a certain extent, the consumption of cleaning chemicals can be reduced, the operation efficiency of the production line can be realized, and the purpose of reducing production cost can be realized.

[0007] Therefore, it is of great significance to develop an additive with strong cleaning ability, which can not only reduce the cleaning steps and time, reduce the chemical consumption in the production process, improve the operation efficiency of the production line, reduce the production cost, but also effectively help the process stability and improve the battery efficiency.

[0008] Practical new type content

[0009] The purpose of the utility model is to provide a single crystal silicon etching additive with strong contamination cleaning ability and etching method, which needs rough polishing process, and can realize the etching cleaning of the single crystal silicon wafer with serious dirt pollution through one-step etching, and has the advantages of high stability, large window, strong cleaning ability, uniform texture and the like. The dependence on front and rear cleaning chemicals is reduced, the service life of the cleaning tank chemicals is prolonged, the chemical consumption in the production process is effectively reduced, and the abnormal fluctuation of the production line and EL defect are reduced.

[0010] To solve the above technical problems, the purpose of the utility model is realized as follows:

[0011] The application relates to a single crystal silicon etching additive with strong contamination cleaning ability, which comprises:

[0012] On the basis of the above scheme and as the preferred scheme of the above scheme: the macromolecular sugar is one or a combination of several of methyl cellulose, hydroxyethyl cellulose, carboxymethyl-B-cyclodextrin, gum arabic, gum, sodium alginate.

[0013] Further preferred are methyl cellulose and carboxymethyl-B-cyclodextrin. The velvet natural macromolecular sugar is selected from one or both of carboxymethyl-B-cyclodextrin and methyl cellulose, both of which are polyhydroxy substances, can be adsorbed on the silicon wafer to form nucleation points, and serve as a mask to help form a microstructure on the surface.

[0014] Since the number of dangling bonds on the Si(100) plane is more than that on the Si(111) plane, the etching rate on the Si(100) plane is faster. Carboxymethyl-B-cyclodextrin is prepared from cyclodextrin by further modification. Since the hydroxyl groups are concentrated on the outside of the carboxymethyl-B-cyclodextrin molecule, the outer wall has strong hydrophilicity, and therefore has strong adsorption capacity on the silicon(100) plane, forming a barrier layer on the surface of the monocrystalline silicon wafer. It strongly hinders the migration of OH ions from the etching solution to the silicon interface, can delay the reaction, and slow down the etching rate. This behavior is conducive to the stability of the texturing reaction process. On the other hand, carboxymethyl-B-cyclodextrin can increase the viscosity of the etching solution, and the hollow structure of the inner cavity effectively separates the hydrogen bubbles attached to the silicon surface, increases the uniformity and coverage of the silicon surface pyramids, and effectively improves the large and small velvet surfaces caused by insufficient defoaming.

[0015] On the basis of the above scheme and as a preferred scheme of the above scheme: the velvet adjusting agent is one or a combination of several of gelatin, polyvinyl alcohol, polyacrylamide, or polyvinylpyrrolidone.

[0016] On the basis of the above scheme and as a preferred scheme of the above scheme: the cleaning aid is one or a combination of several of methyl methacrylate-methyl acrylate copolymer, acrylic acid-dilute propyl alcohol copolymer, propylene ether copolymer, sodium tripolyphosphate, sodium tetrapolyphosphate, and sodium citrate.

[0017] Further preferred, the cleaning aid is one or both of polyvinyl alcohol and polyvinylpyrrolidone. The velvet adjusting agent is polyvinylpyrrolidone and polyvinyl alcohol. The adsorption of macromolecular sugars on the surface of the silicon wafer is unstable, resulting in excessively large pyramid sizes and insufficient nucleation density, leading to high reflectivity and poor light capture ability. The velvet adjusting agent is needed to further adjust. Polyvinyl alcohol is also a hydrophilic polyhydroxy macromolecule that can effectively form hydrogen bonds with the silicon wafer, enhancing the texturing efficiency and adjusting the size, and obtaining uniform and small size. Polyvinylpyrrolidone is an effective dispersant. Due to its different charges and the lone electron structure on the N atom, it can be adsorbed on the surface of the silicon wafer through electrostatic interaction with Si atoms, serving as a supplement to the macromolecular sugars and forming a complete, uniform, and high-specific-surface-area velvet.

[0018] As a preferred solution of the above solution, the anionic surfactant is one or a combination of the following: sodium dodecyl sulfate, sodium dodecyl benzene sulfonate, sodium stearate, and sodium stearoyl glutamate.

[0019] Further preferably, the cleaning aid is one or both of sodium tripolyphosphate and sodium citrate, wherein the sodium tripolyphosphate can form a ring complex with metal ions, reduce water hardness, and greatly enhance the dirt removal capability of the silicon wafer when compounded with the anionic surfactant.

[0020] As a preferred solution of the above solution, the inorganic base is one or a combination of the following: sodium hydroxide, potassium hydroxide, sodium carbonate, sodium phosphate, and sodium acetate.

[0021] Further preferably, the anionic surfactant is one or both of sodium dodecyl sulfate and sodium dodecyl benzene sulfonate, wherein the sulfonic acid in the sodium dodecyl benzene sulfonate protects the pyramid structure formed by bonding with the dangling bond on the (111) plane and reduces the reaction rate by bonding with the dangling bond on the (100) plane, thereby ensuring the formation of a uniform and dense pyramid structure on the surface of the silicon wafer; as a surfactant, the sodium dodecyl benzene sulfonate can effectively control the etching rate and adjust the pyramid size, so that the nucleation points are dense and uniform; meanwhile, when compounded with other anionic surfactants, the fatty chain on the other end has a certain dispersion in the hydrophobic liquid, reduces the surface tension, and quickly removes the silicates on the surface of the silicon wafer to ensure the uniformity of the etching process; after the reaction is completed, the sulfonic acid group near the end surface of the silicon wafer is attracted by van der Waals force, and this loose connection can quickly remove the contamination and residual liquid from the silicon wafer, thereby ensuring the uniformity of the textured surface and the cleanliness of the appearance of the silicon wafer.

[0022] The present application also relates to a method for texturing a single crystal silicon wafer with strong contamination cleaning capability, which comprises the following steps:

[0023] (1) preparing a texturing additive by uniformly mixing natural macromolecular sugars, a texturing regulator, a cleaning aid, a surfactant, an inorganic base, and deionized water;

[0024] (2) preparing a texturing liquid by uniformly mixing the texturing additive prepared in the above step with an alkali solution;

[0025] (3) texturing by putting the single crystal silicon wafer into a pure water pre-cleaning tank, adding hydrogen peroxide and alkali, uniformly mixing, and then adding the texturing liquid for surface texturing; after the texturing is completed, the silicon wafer is washed with deionized water and dried to obtain a textured silicon wafer.

[0026] The utility model discloses a beneficial effect is: the present application relates to a kind of single crystal silicon with strong contamination cleaning ability's method of adding agent and making wool, macromolecular saccharide can be adsorbed on silicon wafer and form nucleation point, as mask, help surface form microstructure.Washing aid is on the surface of silicon wafer and Si atom by electrostatic interaction, adsorbed on the surface of silicon wafer as supplement, and its macromolecular saccharide synergistic effect forms complete uniform and has high specific surface area's wool surface.Anionic surfactant reduces surface tension, quickly desorbs silicate on the surface of silicon wafer to ensure the uniformity of etching process;After reaction, sulfonic acid group is close to the end surface of silicon wafer and relies on van der waals force attraction, this not firm connection can quickly take away the contamination and residual liquid of silicon wafer, ensure the uniformity of wool surface and the appearance cleanliness of silicon wafer. BRIEF DESCRIPTION OF DRAWINGS

[0027] Fig. 1 is the SEM diagram of the wool surface prepared in Example 1;

[0028] Fig. 2 is the SEM diagram of the wool surface prepared in Example 2;

[0029] Fig. 3 is the SEM diagram of the wool surface prepared in Example 3. DETAILED DESCRIPTION

[0030] The utility model is further illustrated in connection with the drawings and specific embodiments.

[0031] The present application relates to a kind of single crystal silicon with strong contamination cleaning ability's method of adding agent, including:

[0032] Example 1

[0033] The present application relates to a kind of single crystal silicon with strong contamination cleaning ability's method of making wool, including the following steps:

[0034] (1) preparation of making wool additive: according to total 100 parts, 1.0 parts of methyl cellulose, 0.1 parts of polyvinyl alcohol, 0.5 parts of tripolyphosphoric acid, 0.09 parts of sodium dodecyl benzene sulfonate, 1.0 parts of inorganic alkali, the rest is deionized water and is uniformly mixed, and making wool additive is prepared.

[0035] (2) preparation of making wool liquid: first, 0.9wt% NaOH solution is prepared in the making wool tank containing 20L pure water, and the making wool additive in step (1) is added to the alkali-containing solution in the proportion of 0.5:100 by mass percentage, mixed uniformly, and bubbled for 2min, to prepare the making wool liquid.

[0036] (3) Texturing: Put the 182 size single crystal silicon wafer into the 20L pure water pre-cleaning tank, and add hydrogen peroxide, sodium hydroxide and water in the tank according to the mass percentage of 1.2:0.5:100. After bubbling for 2min, mix uniformly to perform surface texturing at a temperature of 82℃ for 420s. After texturing, wash the silicon wafer with a large amount of deionized water for 30s, and then dry to obtain the texturing silicon wafer.

[0037] Example 2

[0038] The single crystal silicon texturing method with strong contamination cleaning capacity disclosed in the embodiment comprises the following steps:

[0039] (1) Prepare the texturing additive: uniformly mix 1.0 part of methyl cellulose, 0.1 part of polyvinyl alcohol, 0.0 part of tripolyphosphoric acid, 0.0 part of sodium dodecyl benzene sulfonate, 1.0 part of inorganic alkali, and the rest deionized water according to a total of 100 parts to obtain the texturing additive.

[0040] (2) Prepare the texturing solution: first prepare a 0.9wt% NaOH solution in the texturing tank containing 20L pure water, and then add the texturing additive in step (1) into the alkali solution according to the mass percentage of 0.5:100, mix uniformly, and bubble for 2min to obtain the texturing solution.

[0041] (3) Texturing: put the 182 size single crystal silicon wafer into the 20L pure water pre-cleaning tank, and add hydrogen peroxide, sodium hydroxide and water in the tank according to the mass percentage of 1.2:0.5:100. After bubbling for 2min, mix uniformly to perform surface texturing at a temperature of 82℃ for 420s. After texturing, wash the silicon wafer with a large amount of deionized water for 30s, and then dry to obtain the texturing silicon wafer.

[0042] Example 3

[0043] The single crystal silicon texturing method with strong contamination cleaning capacity disclosed in the embodiment comprises the following steps:

[0044] (1) Prepare the texturing additive: uniformly mix 1.2 parts of carboxymethyl-B-cyclodextrin, 0.15 parts of polyvinyl alcohol, 0.5 parts of tripolyphosphoric acid, 0.15 parts of sodium dodecyl benzene sulfonate, 1.0 part of inorganic alkali, and the rest deionized water according to a total of 100 parts to obtain the texturing additive.

[0045] (2) Prepare the texturing solution: first prepare a 0.9wt% NaOH solution in the texturing tank containing 20L pure water, and then add the texturing additive in step (1) into the alkali solution according to the mass percentage of 0.5:100, mix uniformly, and bubble for 2min to obtain the texturing solution.

[0046] (3) Texturing: Put the 182 size single crystal silicon wafer into the 20L pure water pre-cleaning tank, and add hydrogen peroxide, sodium hydroxide and water into the tank according to the mass percentage of 0.6:0.5:100. After bubbling for 2 minutes, mix uniformly to perform surface texturing at a temperature of 82°C for 420 seconds. After texturing, wash the silicon wafer with a large amount of deionized water for 30 seconds, and then dry to obtain the texturing silicon wafer.

[0047] Example 4

[0048] The single crystal silicon texturing method with strong contamination cleaning capacity disclosed in the embodiment comprises the following steps:

[0049] (1) Prepare the texturing additive: uniformly mix 2.0 parts of carboxymethyl-B-cyclodextrin, 0.08 parts of polyvinyl alcohol, 0.5 parts of tripolyphosphoric acid, 0.15 parts of sodium dodecyl benzene sulfonate, 1.0 parts of inorganic alkali, and the rest deionized water according to a total of 100 parts to obtain the texturing additive.

[0050] (2) Prepare the texturing solution: first prepare a 0.9wt% NaOH solution in the texturing tank containing 20L pure water, and then add the texturing additive in step (1) into the alkali solution according to a mass percentage of 0.5:100, mix uniformly, bubble for 2 minutes, and mix uniformly to obtain the texturing solution.

[0051] (3) Texturing: put the 182 size single crystal silicon wafer into the 20L pure water pre-cleaning tank, and add hydrogen peroxide, sodium hydroxide and water into the tank according to the mass percentage of 0.6:0.5:100. After bubbling for 2 minutes, mix uniformly to perform surface texturing at a temperature of 82°C for 420 seconds. After texturing, wash the silicon wafer with a large amount of deionized water for 30 seconds, and then dry to obtain the texturing silicon wafer.

[0052] Example 5

[0053] The single crystal silicon texturing method with strong contamination cleaning capacity disclosed in the embodiment comprises the following steps:

[0054] (1) Prepare the texturing additive: uniformly mix 0.8 parts of carboxymethyl-B-cyclodextrin, 0.5 parts of methyl cellulose, 0.05 parts of polyvinyl alcohol, 0.5 parts of tripolyphosphoric acid, 0.20 parts of sodium dodecyl benzene sulfonate, 1.0 parts of inorganic alkali, and the rest deionized water according to a total of 100 parts to obtain the texturing additive.

[0055] (2) Prepare the texturing solution: first prepare a 0.9wt% NaOH solution in the texturing tank containing 20L pure water, and then add the texturing additive in step (1) into the alkali solution according to a mass percentage of 0.5:100, mix uniformly, bubble for 2 minutes, and mix uniformly to obtain the texturing solution.

[0056] (3) Texturing: Put the 182 size single crystal silicon wafer into 20L pure water pre-cleaning tank, add hydrogen peroxide, sodium hydroxide and water into the tank according to the mass percentage of 0.6:0.5:100, mix uniformly after bubbling for 2min, and then carry out surface texturing at a temperature of 82℃ for 420s. After texturing, remove the silicon wafer and rinse it with a large amount of deionized water for 30s, and then dry it to obtain a textured silicon wafer.

[0057] The specific use amount of each component in Examples 1 to 5 is shown in Table 1.

[0058] Examples 1 and 5 were tested, and the results are shown in Table 2.

[0059] In Example 1, as shown in FIG. 1, a relatively complete textured surface can be obtained, and the appearance is clean, the pyramid size is 1.8um, and the reflectivity is 9.35%; in Example 2, without the help of cleaning aids and surfactants, as shown in FIG. 2, the surface residues cause the pyramids in some local areas to be unable to be generated or the pyramids to have incomplete morphology, which affects the structure size and uniformity of the pyramids, thereby causing the local reflectivity to be high, and the pyramid size and reflectivity are 1.3um and 10.02% respectively; in Example 3, as can be seen, after the amount of hydrogen peroxide in the pre-cleaning is reduced by half, as shown in FIG. 3, a relatively good effect can still be obtained for the wafer with serious pollution by one-step texturing, and the surface is free of residues, and the pyramid size and reflectivity are 1.6um and 9.38% respectively. In Examples 4 and 5, a uniform and complete textured surface and a good appearance can still be obtained under the condition of lower hydrogen peroxide.

[0060] As shown in Table 3, by testing the small sample of Example 1 using the production line of a perc cell wafer manufacturer, an efficiency of 23.77% can be obtained, which can meet the needs of commercial production.

[0061] Therefore, by adding cleaning aids and surfactants, a clean appearance with uniform color and a complete and dense textured surface can be obtained by one-step texturing without rough polishing, and a good appearance and textured surface can also be obtained under the condition of low hydrogen peroxide consumption, which successfully solves the texturing effect of wafers with serious pollution, and is conducive to the texturing process of wafers with serious pollution and without rough polishing process. In addition, the consumption of cleaning hydrogen peroxide can be significantly reduced, and a relatively good texturing effect can still be obtained.

[0062] The preferred embodiments of the present application are described in detail above. It should be understood that those skilled in the art can make many modifications and changes without creative labor based on the concept of the present application. Therefore, any technical solutions obtained by logical analysis, reasoning or limited experiments based on the existing technology within the concept of the present application shall be within the protection scope defined by the claims.

Claims

1. A single crystal silicon texturing additive having strong contamination cleaning ability, characterized by, The macromolecular sugar includes one or a combination of the following: methyl cellulose, hydroxyethyl cellulose, carboxymethyl-B-cyclodextrin, gum arabic, gum, sodium alginate.

2. The single crystal silicon texturing additive with strong contamination cleaning ability according to claim 1, characterized in that, The suede conditioner includes one or a combination of the following: gelatin, polyvinyl alcohol, polyacrylamide or polyvinylpyrrolidone.

3. The single crystal silicon texturing additive with strong contaminated cleaning ability according to claim 1, characterized in that, The cleaning aid includes one or a combination of the following: methacrylic acid-methyl acrylate copolymer, acrylic acid-dilute propyl alcohol copolymer, propylene ether copolymer, sodium tripolyphosphate, sodium tetraphosphate, sodium citrate.

4. The single crystal silicon texturing additive with strong contaminated cleaning ability according to claim 1, characterized in that, The anionic surfactant includes one or a combination of the following: sodium dodecyl sulfate, sodium dodecyl benzene sulfonate, sodium stearate, sodium stearoyl glutamate.

5. The single crystal silicon texturing additive with strong contaminated cleaning ability according to claim 1, characterized in that, The inorganic base includes one or a combination of the following: sodium hydroxide, potassium hydroxide, sodium carbonate, sodium phosphate, sodium acetate.

6. The single crystal silicon texturing additive with strong contaminated cleaning ability according to claim 1, characterized in that, The method includes the following steps:

7. A single crystal silicon texturing method having a strong contaminant cleaning ability, characterized by, (1) Preparing the suede additive: uniformly mixing the natural macromolecular sugar, the suede conditioner, the cleaning aid, the surfactant, the inorganic base and the deionized water to prepare the suede additive; (2) Preparing the suede solution: uniformly mixing the suede additive prepared in the previous step with the alkali solution to prepare the suede solution; (3) Suede preparation: putting the single crystal silicon wafer into a pure water pre-cleaning tank, adding hydrogen peroxide and alkali, uniformly mixing, and then adding the suede solution to perform surface suede preparation; after the suede preparation is completed, the silicon wafer is washed with deionized water and dried to obtain the suede silicon wafer. ​

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