A high-reflective single-crystal silicon alkali polishing additive, alkali polishing liquid, and preparation method and use thereof

Abstract

The present invention provides a high-reflectivity single-crystal silicon alkali polishing additive, an alkali polishing liquid, a preparation method, and uses. The high-reflectivity single-crystal silicon alkali polishing additive comprises the following components in parts by mass: 1-2 parts of a protective agent; 1-5 parts of a polishing agent; 0.1-1 parts of a surfactant; 0.5-2 parts of a corrosion inhibitor; and 60-80 parts of deionized water. The protective agent is a silyl ether compound; the polishing agent is a lithium-containing compound; the surfactant is one or more of dodecyl glucoside, decyl glucoside, pyranose glucoside, and o-nitrophenyl-β-D-pyranose galactoside; and the corrosion inhibitor is one or more of polyglutamic acid, polylysine, m-hydroxybenzoic acid, and p-hydroxybenzoic acid. The alkali polishing liquid to which the alkali polishing additive is added can improve the polishing effect of silicon wafers, achieve highly selective corrosion, and ultimately obtain single-crystal silicon wafers with a highly reflective back-polished surface, thereby improving the conversion efficiency of solar cells.

Description

Technical Field

[0001] The present invention relates to an alkali polishing technology, in particular to a high-reflection single-crystal silicon alkali polishing additive, an alkali polishing solution, and a preparation method and application thereof. Background Art

[0002] With the continuous advancement of solar cell technology, the requirements for the surface quality and performance of monocrystalline silicon wafers are increasing. Alkali polishing of monocrystalline silicon wafers is a key step in the solar cell manufacturing process, directly affecting the wafer's surface flatness, reflectivity, and ultimately the cell's conversion efficiency. The goal of the alkaline polishing process is to remove defects and contaminants from the wafer surface, achieving a certain level of flatness and micro-roughness, which is beneficial for cell fabrication and electron migration. Alkali polishing typically uses sodium hydroxide or potassium hydroxide as the treatment solution to control the roughness of different wafers. During the alkaline polishing process, non-uniform corrosion often occurs due to the polarity and concentration of the reactants. In this case, chemical additives are needed to evenly distribute the reaction solution across the wafer surface, thereby achieving a uniform surface roughness.

[0003] During the alkaline polishing process, additives can form a certain dispersion system, control the viscosity and surface tension of the reaction liquid, and reduce surface defects and non-uniform corrosion. In addition, additives can also form a protective film to protect the surface of the silicon wafer from excessive corrosion, thereby achieving precise control of the surface roughness of the silicon wafer. Another function of the alkaline polishing additive is to improve the interaction between the reaction liquid and the surface of the silicon wafer, so that the desired microstructure is formed on the surface of the silicon wafer. By adjusting the concentration and pH conditions of substances such as sodium hydroxide or potassium hydroxide, the purpose of adjusting the reaction speed of the silicon wafer surface is achieved, thereby improving the conversion efficiency of the silicon wafer. Therefore, the development of high-reflectivity single-crystal silicon alkaline polishing additives is of great significance for improving the performance of solar cells. Summary of the Invention

[0004] The purpose of the present invention is to address the problem that the polishing effect of the current alkaline polishing solution needs to be improved, and to propose a high-reflectivity single-crystal silicon alkaline polishing additive. Adding the alkaline polishing additive to the alkaline polishing solution can improve the polishing effect of the silicon wafer, achieve highly selective corrosion, and ultimately obtain a single-crystal silicon wafer with a highly reflective back-polished surface, thereby improving the conversion efficiency of solar cells.

[0005] To achieve the above object, the technical solution adopted by the present invention is: a high-reflectivity single-crystal silicon alkali polishing additive, comprising the following components in parts by weight:

[0006] 1-2 parts of protective agent;

[0007] 1-5 parts of polishing agent;

[0008] 0.1-1 part of surfactant;

[0009] Corrosion inhibitor 0.5-2 parts;

[0010] 60-80 parts of deionized water;

[0011] The protective agent is a silyl ether compound;

[0012] The polishing agent is a lithium-containing compound.

[0013] Furthermore, the protective agent is one or more of tert-butyldimethylsilyl glycidyl ether, tert-butyldimethylallylsilyl ether and 1,3-bis(aminopropyl)tetramethyldisiloxane.

[0014] Furthermore, the protective agent is preferably tert-butyldimethylsilyl glycidyl ether.

[0015] Furthermore, the protective agent is 1.5-2 parts.

[0016] The protective agent in the high-reflectivity single-crystal silicon alkali polishing additive of the present invention is a silyl ether compound, the silyl group contained in which can chemically react with the hydroxyl group (-OH) or other active groups on the silicon surface to form a protective film on the surface of the silicon wafer, thereby reducing damage to the silicon wafer surface during the polishing process and protecting the PN junction on the front side of the silicon wafer from being destroyed.

[0017] Furthermore, the polishing agent is one or more of lithium methacrylate, lithium hexafluorophosphate and isopropylmagnesium chloride-lithium chloride.

[0018] Furthermore, the polishing agent is preferably lithium methacrylate.

[0019] Furthermore, the polishing agent is 3-5 parts.

[0020] The polishing agent in the high-reflectivity single-crystal silicon alkaline polishing additive of this invention utilizes the isotropy of lattice atoms to flatten the textured pyramids while simultaneously removing back- and surrounding borosilicate glass from boron diffusion. Furthermore, the protective agent and polishing agent work synergistically. On the one hand, the silane ether compound reacts with the lithium compound to form silanols (Si-OH) or silanes (Si-H), which form silicon-oxygen bonds with silicon atoms on the silicon wafer surface, enhancing the wafer's surface hydrophilicity and wettability. Furthermore, the presence of the protective film allows the polishing agent to polish the silicon wafer surface more evenly and smoothly, improving polishing efficiency and quality.

[0021] Furthermore, the surfactant is one or more of dodecyl glucoside, decyl glucoside, glucopyranoside and o-nitrophenyl-β-D-galactopyranoside.

[0022] Furthermore, the surfactant is preferably glucopyranoside.

[0023] Furthermore, the surfactant is 0.1-0.5 parts.

[0024] The surfactant in the high-reflectivity single-crystal silicon alkali polishing additive of the present invention can reduce the contact angle between the polishing liquid and the silicon wafer surface, making it easier for the polishing liquid to penetrate into the microstructure of the silicon wafer surface, thereby more effectively removing surface defects and pollutants and making the entire surface more uniform.

[0025] Furthermore, the corrosion inhibitor is one or more of polyglutamic acid, polylysine, m-hydroxybenzoic acid and p-hydroxybenzoic acid.

[0026] Furthermore, the corrosion inhibitor is preferably polyglutamic acid.

[0027] Furthermore, the corrosion inhibitor is 0.5-1 part.

[0028] The corrosion inhibitor in the high-reflection single-crystal silicon alkali polishing additive of the present invention can control the reaction rate during the alkali polishing process, reduce the amount of alkali used during the reaction process, and extend the service life of the alkali polishing solution.

[0029] Another object of the present invention is to disclose a method for preparing a highly reflective single-crystal silicon alkali polishing additive, comprising the following steps:

[0030] At room temperature, a protective agent, a polishing agent, a surfactant and a corrosion inhibitor are sequentially added to deionized water, stirred until completely dissolved, and then stirred for 1-2 hours to obtain a high-reflectivity single-crystal silicon alkali polishing additive.

[0031] Another object of the present invention is to disclose the use of a high-reflective single-crystal silicon alkali polishing additive in the field of alkali polishing liquid.

[0032] Another object of the present invention is to disclose an alkali polishing solution, comprising the highly reflective single crystal silicon alkali polishing additive, alkali and deionized water.

[0033] Furthermore, the mass ratio of the high-reflective single-crystal silicon alkali polishing additive, alkali and deionized water in the alkali polishing solution is 0.3-1:0.75-1.5:100.

[0034] Furthermore, the mass ratio of the high-reflective single-crystal silicon alkali polishing additive, alkali and deionized water in the alkali polishing solution is preferably 0.3-0.5:0.75-1:100.

[0035] Furthermore, the mass ratio of the high-reflective single-crystal silicon alkali polishing additive, alkali and deionized water in the alkali polishing solution is more preferably 0.3:1:100.

[0036] Furthermore, the alkali is sodium hydroxide and / or potassium hydroxide.

[0037] Another object of the present invention is to disclose a method for preparing an alkali polishing solution, comprising the following steps: adding a high-reflective single-crystal silicon alkali polishing additive and an alkali into deionized water and stirring and mixing them uniformly to prepare the alkali polishing solution.

[0038] Furthermore, the temperature of the deionized water is 60-65°C.

[0039] Furthermore, the temperature of the deionized water is preferably 62°C.

[0040] Another object of the present invention is to disclose the use of an alkaline polishing solution in the field of silicon wafer polishing.

[0041] Furthermore, the method for polishing a silicon wafer using the alkaline polishing solution is as follows:

[0042] S1: Pre-clean the silicon wafer using a pre-cleaning solution before polishing;

[0043] S2: Soak the pre-cleaned silicon wafer in deionized water for 80-120 seconds, take it out and polish it in an alkaline polishing solution. The polishing time is 190 seconds to 240 seconds, and the polishing temperature is 60° C. to 65° C.

[0044] Furthermore, the pre-cleaning solution in S1 includes alkali, hydrogen peroxide and deionized water.

[0045] Furthermore, the mass ratio of alkali, hydrogen peroxide and deionized water in the pre-cleaning solution in S1 is 0.2-0.5:0.3-1.5:100.

[0046] Furthermore, the mass ratio of alkali, hydrogen peroxide and deionized water in the pre-cleaning solution is preferably 0.2:0.5:100.

[0047] Furthermore, the base in S1 is sodium hydroxide and / or potassium hydroxide.

[0048] Furthermore, the pre-cleaning time in S1 is 110s-250s, and the pre-cleaning temperature is 60°C-63°C.

[0049] Furthermore, the pre-cleaning time in S1 is preferably 190 seconds, and the pre-cleaning temperature is preferably 61°C.

[0050] Furthermore, in S2, the pre-cleaned silicon wafer is immersed in deionized water for 100 seconds.

[0051] Furthermore, the polishing time in S2 is preferably 200 s, and the polishing temperature is preferably 62°C.

[0052] The high-reflective single-crystal silicon alkali polishing additive, alkali polishing solution, preparation method and use of the present invention have the following advantages compared with the prior art:

[0053] 1) The protective agent in the highly reflective single-crystal silicon alkaline polishing additive of the present invention is a silyl ether compound. The silyl groups contained therein react chemically with hydroxyl groups (-OH) or other active groups on the silicon surface, forming a protective film on the silicon wafer surface. This reduces surface damage during polishing and protects the PN junction on the front side of the silicon wafer from destruction. The polishing agent utilizes the isotropy of lattice atoms to flatten the textured pyramids while simultaneously removing back- and surrounding borosilicate glass from boron diffusion. The protective agent and polishing agent act synergistically. On the one hand, the silyl ether compound reacts with the lithium compound to form silanols (Si-OH) or silanes (Si-H), which can form silicon-oxygen bonds with silicon atoms on the silicon wafer surface, enhancing the hydrophilicity and wettability of the silicon wafer surface. On the other hand, the presence of the protective film allows the polishing agent to polish the silicon wafer surface more evenly and smoothly, which helps improve polishing efficiency and quality.

[0054] 2) The surfactant in the high-reflective single-crystal silicon alkali polishing additive of the present invention can reduce the contact angle between the alkali polishing solution and the silicon wafer surface, making it easier for the alkali polishing solution to penetrate into the microstructure of the silicon wafer surface, thereby more effectively removing surface defects and contaminants and making the entire surface more uniform.

[0055] 3) The corrosion inhibitor in the high-reflective single-crystal silicon alkali polishing additive of the present invention can control the reaction rate during the alkali polishing process, reduce the amount of alkali used during the reaction process, and extend the service life of the alkali polishing solution.

[0056] 4) Alkali polishing solution with high-reflective single-crystal silicon alkaline polishing additives can improve the polishing effect of silicon wafers and achieve highly selective corrosion, that is, protecting the silicon oxide coating after boron diffusion on the front side of the silicon wafer from corrosion, and corroding the back side to form a tower base, ultimately obtaining a single-crystal silicon wafer with a highly reflective back-polished surface, thereby improving the conversion efficiency of solar cells. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] Figure 1 This is a dark field optical microscope image magnified 500 times after the back surface was polished using the alkali polishing solution of Example 7;

[0058] Figure 2 This is a 500-fold magnification image of the front side of the polishing process after alkali polishing using the alkali polishing solution of Example 7;

[0059] Figure 3 This is a dark field optical microscope photograph magnified 500 times the back surface after alkali polishing using the alkali polishing solution of Comparative Example 4;

[0060] Figure 4 This is a 500-fold dark-field optical microscope photograph of the front surface after alkali polishing using the alkali polishing solution of Comparative Example 4. DETAILED DESCRIPTION

[0061] The present invention will be further described below with reference to the following examples. The following description of the technical features is based on representative embodiments and specific examples of the present invention, but the present invention is not limited to these embodiments and specific examples. It should be noted that:

[0062] Unless otherwise stated, the units used in this specification are international standard units, and the numerical values and numerical ranges appearing in the present invention should be understood to include the inevitable systematic errors in industrial production.

[0063] In this specification, the numerical range expressed using "a numerical value A to a numerical value B" means a range including the endpoints A and B.

[0064] In this specification, the numerical range expressed using "above" or "below" means a numerical range including the number.

[0065] In this specification, the use of "may" includes both the meaning of performing a certain process and the meaning of not performing a certain process.

[0066] In this specification, the use of "optional" or "optional" indicates that certain substances, components, execution steps, application conditions and other factors are used or not used.

[0067] In this specification, when "normal temperature" or "room temperature" is used, the temperature may be 15-25°C.

[0068] In this manual, the reagents or instruments used without indicating the manufacturer are all conventional products that can be obtained through commercial purchase.

[0069] Examples 1-6

[0070] Examples 1-6 disclose various highly reflective single-crystal silicon alkali polishing additives, the components and mass ratios of which are shown in Table 1. The preparation method is as follows: at room temperature, deionized water is first added to a container, followed by the addition of a protective agent, a polishing agent, a surfactant, and a corrosion inhibitor, followed by stirring until completely dissolved and then stirring for another 2 hours to obtain a highly reflective single-crystal silicon alkali polishing additive.

[0071] Table 1 Components and mass ratios of high reflective single crystal silicon alkali polishing additives of Examples 1-6

[0072]

[0073] Comparative Examples 1-3

[0074] Comparative Examples 1-3 disclose a variety of alkali polishing additives, whose components and mass ratios are shown in Table 2, and their preparation methods are the same as those in Example 1.

[0075] Table 2 Components and mass ratios of alkali polishing additives in comparative examples 1-3

[0076]

[0077] Examples 7-12

[0078] Examples 7-12 disclose a variety of alkali polishing solutions, which respectively include the alkali polishing additives described in Examples 1-6, sodium hydroxide and deionized water, and the mass ratio of the alkali polishing additives, sodium hydroxide and deionized water is 0.3:1:100.

[0079] The preparation method of the alkali polishing solution is as follows: adding a high-reflection single-crystal silicon alkali polishing additive and sodium hydroxide into 62° C. deionized water and stirring and mixing them uniformly to prepare the alkali polishing solution.

[0080] Comparative Examples 4-6

[0081] Comparative Examples 4-6 disclose various alkali polishing solutions, including the alkali polishing additives described in Comparative Examples 1-3, sodium hydroxide, and deionized water, wherein the mass ratio of the alkali polishing additives, sodium hydroxide, and deionized water is 0.3:1:100. The preparation method of the alkali polishing solution is the same as that of Example 7.

[0082] Various properties of the alkali polishing solutions of Examples 7-12 and Comparative Examples 4-6 were tested below.

[0083] Preparation of a pre-cleaning solution: Sodium hydroxide and hydrogen peroxide were added to deionized water at 61° C. and stirred to mix uniformly to prepare a pre-cleaning solution, wherein the mass ratio of sodium hydroxide, hydrogen peroxide and deionized water was 0.2:0.5:100.

[0084] The back side of the single crystal silicon was polished using the alkaline polishing solutions of Examples 7-12 and Comparative Examples 4-6, respectively. The back side polishing method of the single crystal silicon was as follows: first, a boron-expanded single crystal silicon wafer was placed in a 61°C pre-cleaning solution, reacted for 190 seconds, then the silicon wafer was removed and soaked in deionized water for 100 seconds. After removal, the pre-cleaned single crystal silicon wafer was placed in the alkaline polishing solution. After polishing at 62°C for 200 seconds, the silicon wafer was removed and immediately rinsed with deionized water for 20 seconds, then rinsed with ethanol for 10 seconds, and then dried in a 50°C oven.

[0085] Performance testing:

[0086] Average reflectivity test: Use a film thickness meter to measure the absolute reflectivity, and then integrate the obtained data to obtain the weighted average reflectivity.

[0087] Tower base size test: Use an optical microscope in dark field mode to measure the distance between the two long sides of the tower base.

[0088] The performance test data of the alkali polishing solution of Examples 7-12 and Comparative Examples 4-6 are shown in Table 3:

[0089] Table 3 Performance test data

[0090]

[0091] From the data in Table 3, it can be seen that when polishing with the alkaline polishing solutions of Examples 7-12 (alkaline polishing solutions containing the high-reflectivity single-crystal silicon alkaline polishing additives of Examples 1-6, respectively), the tower base sizes of the silicon wafers obtained in Examples 7-12 meet the requirements and have better integrity, thereby achieving higher reflectivity; whereas, the tower base sizes of the silicon wafers obtained with the alkaline polishing solutions of Comparative Examples 4-6 (alkaline polishing solutions containing the alkaline polishing additives of Comparative Examples 1-3, respectively) are smaller, have poorer integrity, and have lower reflectivity, which will lead to poor subsequent battery performance.

[0092] Example 7 Alkaline polishing solution is used to polish the back of the silicon wafer tower base (see Figure 1 ) than the silicon wafer back tower base obtained by using the alkaline polishing solution of Comparative Example 4 (see Figure 3 ) is more uniform and complete, the front side velvet surface of the silicon wafer obtained by polishing with alkaline polishing solution in Example 7 (see Figure 2 ) than the front velvet surface of the silicon wafer obtained by using the alkaline polishing solution of Comparative Example 4 (see Figure 4 ) has better protection, that is, the front silicon oxide film is not corroded, and the alkaline polishing solution in Example 7 achieves protection of the front suede surface.

[0093] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A high reflective single crystal silicon alkali polishing additive, characterized in that: The composition comprises the following components in parts by mass: 1-2 parts of protective agent; 1-5 parts of polishing agent; 0.1-1 part of surfactant; Corrosion inhibitor 0.5-2 parts; 60-80 parts of deionized water; The protective agent is one or more of tert-butyldimethylsilyl glycidyl ether, tert-butyldimethylallylsilyl ether and 1,3-bis(aminopropyl)tetramethyldisiloxane; The polishing agent is one or more of lithium methacrylate, lithium hexafluorophosphate and isopropyl magnesium chloride-lithium chloride; The surfactant is one or more of dodecyl glucoside, decyl glucoside, glucopyranoside and o-nitrophenyl-β-D-galactopyranoside; The corrosion inhibitor is one or more of polyglutamic acid, polylysine, m-hydroxybenzoic acid and p-hydroxybenzoic acid.

2. A method for preparing the highly reflective single-crystal silicon alkali polishing additive according to claim 1, characterized in that: The following steps are involved: At room temperature, a protective agent, a polishing agent, a surfactant and a corrosion inhibitor are sequentially added to deionized water, stirred until completely dissolved, and then stirred for 1-2 hours to obtain a high-reflectivity single-crystal silicon alkali polishing additive.

3. Use of the high-reflective single-crystal silicon alkali polishing additive according to claim 1 in the field of alkali polishing liquid.

4. An alkali polishing solution, characterized in that The method comprises the high-reflective single-crystal silicon alkali polishing additive according to claim 1, alkali and deionized water; The mass ratio of the high-reflection single-crystal silicon alkali polishing additive, alkali and deionized water in the alkali polishing solution is 0.3-1:0.75-1.5:

100.

5. Alkali polishing liquid according to claim 4, characterized in that The alkali is sodium hydroxide and / or potassium hydroxide.

6. A method for preparing the alkali polishing solution according to claim 4, characterized in that: The method comprises the following steps: adding a high-reflection single-crystal silicon alkali polishing additive and alkali into deionized water, stirring and mixing the mixture evenly to prepare an alkali polishing solution.

7. Use of the alkaline polishing solution according to claim 4 or 5 in the field of silicon wafer polishing.

8. The use according to claim 7, characterized in that: The method for polishing silicon wafers using the alkaline polishing solution is as follows: S1: Pre-clean the silicon wafer using a pre-cleaning solution before polishing; S2: Soak the pre-cleaned silicon wafer in deionized water, take it out and polish it in an alkaline polishing solution. The polishing time is 190s-240s and the polishing temperature is 60°C-65°C.

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