Etching Solution, Usage Method and Application for Borosilicate Glass Layer of Silicon Wafer

Abstract

The present invention discloses an etching solution, a usage method and an application for a boron-silicate glass layer of a silicon wafer. The etching solution for the boron-silicate glass layer of the silicon wafer includes HF, water, HCl, an oxidizing agent and an alkali polishing additive. Through the synergistic effect of the components in the etching solution, the etching solution of the present application can, while ensuring that the front side of the silicon wafer is not affected by the etching solution, effectively etch the side and back sides of the silicon wafer even when the edge of the silicon wafer is doped with silicon nitride, silicon oxynitride or not fully oxidized resulting in a high boron concentration, improving the yield and efficiency of the silicon wafer.

Description

Technical Field

[0001] The present invention relates to the technical field of solar cell manufacturing, and more particularly, to an etching solution for a boron-silicate glass layer of a silicon wafer, a usage method, and an application. Background Art

[0002] With the increasingly fierce market competition of solar cells, high-efficiency cells have become the main direction of research and development in the solar energy industry. During the preparation process of solar cells, it is necessary to remove the boron-silicate glass layer on the back and sides of the silicon wafer.

[0003] Currently, the chain machine on the market mainly removes the BSG layer on the sides of the silicon wafer, and the formula is mainly HF and water. Under normal circumstances, it can meet the requirements. However, when the silicon wafer edge is doped with silicon nitride, silicon oxynitride, or the boron concentration is high due to incomplete oxidation, the sides cannot be effectively removed.

[0004] In view of this, the present invention is specifically proposed. Summary of the Invention

[0005] The purpose of the present invention is to provide an etching solution for a boron-silicate glass layer of a silicon wafer, a usage method, and an application. When the silicon wafer edge is doped with silicon nitride, silicon oxynitride, or the boron concentration is high due to incomplete oxidation, using the etching solution of the present invention is beneficial to ensure sufficient etching of the doped silicon nitride, doped silicon oxynitride, or the region with high boron concentration on the edge or side of the silicon wafer, and at the same time, it will not react with the front side of the silicon wafer.

[0006] The present invention is implemented as follows:

[0007] In a first aspect, the present invention provides an etching solution for a boron-silicate glass layer of a silicon wafer, comprising the following components:

[0008]

[0009] In an optional embodiment, the oxidant is selected from at least one of inorganic acids without metal ions, sodium salts with oxidizing properties, or potassium salts with oxidizing properties.

[0010] In an optional embodiment, the oxidant is selected from at least one of hydrogen peroxide, nitric acid, sulfuric acid, chloric acid, chlorous acid, perchloric acid, nitrous acid, sodium chlorate, potassium chlorate, sodium chlorite, potassium chlorite, sodium perchlorate, and potassium perchlorate.

[0011] In an optional embodiment, the oxidant is hydrogen peroxide.

[0012] In an optional embodiment, the model of the alkali polishing additive is at least one of PR21, BP21, BPL819, and BPL829, and the concentration of the alkali polishing additive in the etching solution is 7.6 vol% - 7.8 vol%.

[0013] In an alternative embodiment, the concentration of HF in the etching solution is 0.24 g / ml - 0.25 g / ml.

[0014] In an alternative embodiment, the concentration of HCl in the etching solution is 0.083 g / ml - 0.084 g / ml.

[0015] In an alternative embodiment, the concentration of the oxidant in the etching solution is 0.040 g / ml - 0.041 g / ml.

[0016] In a second aspect, the present invention provides a method for using the etching solution for the borosilicate glass layer of a silicon wafer according to any one of the foregoing embodiments, wherein the back surface of the silicon wafer covered with the borosilicate glass layer is immersed in the etching solution for etching.

[0017] In a third aspect, the present invention provides an application of the etching solution for the borosilicate glass layer of a silicon wafer according to any one of the foregoing embodiments in removing the borosilicate glass layer on the back surface and / or side surface of the silicon wafer.

[0018] The present invention has the following beneficial effects:

[0019] Through the synergistic effect of the components in the etching solution of the present application, while ensuring that the front surface of the silicon wafer is not affected by the etching solution, even when the silicon wafer edge is doped with silicon nitride, silicon oxynitride or has a high boron concentration due to incomplete oxidation, the side surface and the back surface of the silicon wafer can be effectively etched, improving the yield and efficiency of the silicon wafer. Description of the Drawings

[0020] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention, and therefore should not be regarded as limiting the scope. For those of ordinary skill in the art, other related drawings can be obtained based on these drawings without creative efforts.

[0021] Figure 1 Is the morphology of the silicon wafer after etching with the etching solution described in Example 1;

[0022] Figure 2 Is the morphology of the silicon wafer after etching with the etching solution described in Comparative Example 1. Detailed Embodiments

[0023] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. For those conditions not specified in the embodiments, they are carried out according to conventional conditions or the conditions recommended by the manufacturer. For the reagents or instruments not specified by the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0024] An embodiment of the present invention provides an etching solution for a boron-silicate glass layer of a silicon wafer, comprising the following components:

[0025]

[0026] Generally, after diffusion of the silicon wafer, it is necessary to remove the boron-silicate glass layers on the back and side surfaces while ensuring that the front surface is not etched. To remove the boron-silicate glass layer on the surface of the silicon wafer, the back surface of the silicon wafer is placed in the etching solution, which is usually HF + water. During etching, the back surface of the silicon wafer is immersed in the etching solution, and the edge of the silicon wafer contacts and reacts with the etching solution by the surface tension of the etching solution, etc. However, when the edge of the silicon wafer is doped with silicon nitride, silicon oxynitride, or boron concentration is high due to incomplete oxidation, if the back surface of the silicon wafer is etched completely, the edge of the silicon wafer has poor etching effect due to difficult etching and insufficient contact with the etching solution, which will lead to a decrease in the yield and efficiency of the silicon wafer.

[0027] The etching solution for the boron-silicate glass layer of the silicon wafer provided by the embodiment of the present invention includes HF, water, HCl, an oxidant, and an alkali polishing additive. Among them, HF is used to remove the boron-silicate glass layer on the surface of the silicon wafer, the oxidant can oxidize the uncompletely oxidized boron, hydrochloric acid is used to provide an acidic environment on the one hand and can complex with metal ions in the system on the other hand, and the alkali polishing additive contains a surfactant, sodium silicate, and various additive components, which can change the wettability between the etching solution and the edge of the silicon wafer. Through the synergistic effect of each component in the etching solution, while ensuring that the front surface of the silicon wafer is not affected by the etching solution, even when the edge of the silicon wafer is doped with silicon nitride, silicon oxynitride, or boron concentration is high due to incomplete oxidation, the side and back surfaces of the silicon wafer can be effectively etched, improving the yield and efficiency of the silicon wafer.

[0028] In an alternative embodiment, the oxidant is selected from at least one of inorganic acids without metal ions, sodium salts with oxidizing properties, or potassium salts with oxidizing properties, minimizing the introduction of metal ions other than sodium and potassium in the etching solution, which is beneficial to ensuring the etching effect.

[0029] In an alternative embodiment, the oxidant is selected from at least one of hydrogen peroxide, nitric acid, sulfuric acid, chloric acid, chlorous acid, perchloric acid, nitrous acid, sodium chlorate, potassium chlorate, sodium chlorite, potassium chlorite, sodium perchlorate, and potassium perchlorate, without metal ions other than sodium and potassium, which is beneficial to ensuring the etching effect.

[0030] In an alternative embodiment, the oxidant is hydrogen peroxide, which has a good effect on improving the yield and efficiency of the silicon wafer.

[0031] In an alternative embodiment, the type of the alkali etch additive is at least one of PR21, BP21, BPL819, and BPL829, and the concentration of the alkali etch additive in the etchant is 7 vol% - 8.5 vol%. Specifically, it can be 7 vol%, 7.5 vol%, 8 vol%, 8.5 vol%, or any value between 7 vol% - 8.5 vol%. In some preferred embodiments, it can be 7.6 vol% - 7.8 vol% to further optimize the composition of the etchant.

[0032] In an alternative embodiment, the concentration of HF in the etchant is 0.22 g / ml - 0.26 g / ml. Specifically, it can be 0.22 g / ml, 0.23 g / ml, 0.24 g / ml, 0.25 g / ml, 0.26 g / ml, or any value between 0.22 g / ml - 0.26 g / ml. In some preferred embodiments, it can be 0.24 g / ml - 0.25 g / ml to further optimize the composition of the etchant.

[0033] In an alternative embodiment, the concentration of HCl in the etchant is 0.075 g / ml - 0.090 g / ml. Specifically, it can be 0.075 g / ml, 0.080 g / ml, 0.085 g / ml, 0.090 g / ml, or any value between 0.075 g / ml - 0.090 g / ml. In some preferred embodiments, it can be 0.083 g / ml - 0.084 g / ml.

[0034] In an alternative embodiment, the concentration of the oxidant in the etchant is 0.035 g / ml - 0.045 g / ml. Specifically, it can be 0.035 g / ml, 0.037 g / ml, 0.039 g / ml, 0.041 g / ml, 0.043 g / ml, 0.045 g / ml, or any value between 0.035 g / ml - 0.045 g / ml. In some preferred embodiments, it can be 0.040 g / ml - 0.041 g / ml of the oxidant to further optimize the composition of the etchant.

[0035] The embodiments of the present invention also provide a method for using the etchant for the borosilicate glass layer of a silicon wafer described in any one of the foregoing embodiments. The back surface of the silicon wafer covered with the borosilicate glass layer is immersed in the etchant for etching. The etchant will gradually wet the side surface of the silicon wafer, so that the doped silicon nitride, doped silicon oxynitride, or the region with a high boron concentration on the side surface of the silicon wafer can also be etched sufficiently, and at the same time, it will not react with the front surface of the silicon wafer.

[0036] Another application of the etching solution for the borosilicate glass layer of a silicon wafer according to any one of the foregoing embodiments is to remove the borosilicate glass layer on the back and / or side of the silicon wafer.

[0037] The features and properties of the present invention will be further described in detail below in conjunction with embodiments.

[0038] Examples 1 - 5

[0039] The etching solution for the borosilicate glass layer of a silicon wafer provided in Examples 1 - 5 of the present application includes HF, water, HCl, an oxidizing agent, and an alkali polishing additive. The concentrations of the components in the etching solution are shown in Table 1.

[0040] Table 1

[0041] Example HF, g / ml HCl, g / ml <![CDATA[H 2 O 2 ,g / ml]]> Alkaline etching additive PR21, vol% 1 0.2409 0.0835 0.0407 7.69 2 0.24 0.084 0.041 7.6 3 0.25 0.083 0.040 7.8 4 0.22 0.090 0.035 8.5 5 0.26 0.075 0.045 7.0

[0042] Examples 6 - 10

[0043] The etching solution for the borosilicate glass layer of a silicon wafer provided in Examples 6 - 10 of the present application includes HF 0.2409 g / ml, HCl 0.0835 g / ml, an oxidizing agent 0.0407 g / ml, and an alkali polishing additive PR2 17.69 vol%. Among them, the oxidizing agents selected in Examples 6 - 10 are perchloric acid, nitric acid, sulfuric acid, sodium chlorite, and potassium perchlorate, respectively.

[0044] Examples 11 - 13

[0045] The etching solution for the borosilicate glass layer of a silicon wafer provided in Examples 11 - 13 of the present application includes HF 0.2409 g / ml, HCl 0.0835 g / ml, H 2 O 2 0.0407 g / ml, and an alkali polishing additive 7.69 vol%. Among them, the alkali polishing additives selected in Examples 11 - 13 are BP21, BPL819 of Huzhou Sanfeng Energy New Materials Co., Ltd., and BPL829 of Huzhou Sanfeng Energy New Materials Co., Ltd., respectively.

[0046] Comparative Examples 1 - 8

[0047] The etching solution for the borosilicate glass layer of a silicon wafer provided in Comparative Examples 1 - 8 of the present application includes HF, water, HCl, an oxidizing agent, and an alkali polishing additive. The concentrations of the components in the etching solution are shown in Table 2.

[0048] Table 2

[0049]

[0050]

[0051] Comparative Examples 14 - 16

[0052] The etching solution for the boron-silicate glass layer of the silicon wafer provided in Comparative Examples 14-16 of the present application includes HF 0.2409 g / ml, HCl 0.0835 g / ml, H 2 O 2 0.0407 g / ml and surfactant 7.69 vol%, where the surfactants used in Comparative Examples 14-16 are potassium gluconate 0.16%, polyethylene oxide ether 4000 ppb, and sodium lactate 0.06% respectively.

[0053] Place the back side of the silicon wafers diffused under the same diffusion furnace and the same conditions into the etching solutions in the above-mentioned examples and comparative examples for etching. The etching temperature is 25°C and the humidity is 50%. The surface morphologies after etching in Example 1 and Comparative Example 1 are as Figure 1 (The BSG, SixNX, and SixOxNx layers are completely removed) and Figure 2 (There are residues in the BSG, SixNX, and SixOxNx layers) as shown. Then, perform alkali polishing, pepoly, annealing, PSG removal, RCA removal, ALD, coating, and screen printing on the etched silicon wafers to obtain solar cells, and test their yield, efficiency, and average leakage current rate. The results are shown in Table 3.

[0054] Table 3

[0055]

[0056]

[0057]

[0058] Note: When the reverse saturation current of the silicon wafer ≤ 0.3, it is recorded as good; when the reverse saturation current of the silicon wafer > 0.3, it is recorded as bad.

[0059] It can be seen from Table 3 that compared with the comparative examples, the etching solutions in the examples have obvious advantages in improving the yield, efficiency, and leakage current rate of solar cells.

[0060] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. An etching solution for borosilicate glass layer of silicon wafer, characterized in that: With water as solvent, the concentrations of the components are as follows: The model of the alkali polishing additive is PR21, and the oxidant is selected from at least one of hydrogen peroxide, nitric acid and potassium perchlorate.

2. The etching solution for borosilicate glass layer of silicon wafer according to claim 1, characterized in that: The oxidant is hydrogen peroxide.

3. The etching solution for borosilicate glass layer of silicon wafer according to claim 1, characterized in that: The concentration of the alkali polishing additive in the etching solution is 7.6 vol%-7.69 vol%.

4. The etching solution for borosilicate glass layer of silicon wafer according to claim 1, characterized in that: The concentration of HCl in the etching solution is 0.0835 g / ml-0.084 g / ml.

5. The etching solution for borosilicate glass layer of silicon wafer according to claim 1, characterized in that: The concentration of the oxidant in the etching solution is 0.040 g / ml-0.0407 g / ml.

6. A method for using the etching solution for a borosilicate glass layer on a silicon wafer according to any one of claims 1 to 5, characterized in that: The back side of the silicon wafer covered with a borosilicate glass layer is immersed in the etching solution for etching.

7. Use of the etching solution for borosilicate glass layer on silicon wafer according to any one of claims 1 to 5 in removing the borosilicate glass layer on the back and / or side of a silicon wafer.

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