A single-crystalline silicon auxiliary polishing additive and its application

Abstract

The present invention provides a single-crystalline silicon polishing aid additive. By mass ratio, the additive comprises the following components: a co-directional etching promoter 0.5% - 3.0%, an antifoaming agent 1.0% - 5.0%, a cleaning agent 0.5% - 2.0%, a non-ionic surfactant 1.0% - 6.0%, and the balance is deionized water. Further, the present invention also provides the application of the above additive in the single-crystalline silicon rough polishing reaction, that is, mixing the additive with an alkali solution as the reaction solution for the rough polishing of single-crystalline silicon wafers. The additive provided by the present invention is applied to the single-crystalline silicon rough polishing reaction, which can effectively control the reaction rate, help to prompt the generated H2 to quickly detach from the silicon wafer surface during the reaction, and obtain a more flat, uniform and high-efficiency solar cell wafer.

Description

Technical Field

[0001] The present invention belongs to the technical field of surface treatment of single-crystal silicon wafers, and particularly relates to a single-crystal silicon polishing aid additive and its application. Background Art

[0002] With the improvement of solar cell manufacturing technology, heterojunction cells have been favored by the industry due to their advantages such as low process temperature, low temperature coefficient, no light-induced degradation and electro-induced degradation. In the process of manufacturing heterojunctions, the most important step is the deposition of amorphous silicon thin films. High-quality surface passivation is very important for obtaining high-efficiency solar cells. During the surface passivation of amorphous silicon, in order to prevent epitaxial growth at the heterojunction interface, a smooth surface interface of the silicon wafer is required.

[0003] HBC-type cells that incorporate amorphous silicon passivation technology have become a new generation of the most promising battery manufacturing technology with high open-circuit voltage and high conversion efficiency. In the manufacturing process of HBC-type cells, the deposition of amorphous silicon thin films is carried out on the surface of silicon wafers that have been polished. It is required to obtain a silicon wafer surface with smooth and uniform tower bases in the rough polishing step, which is beneficial to improving the deposition coverage rate and interface contact of amorphous silicon. Currently, there are already studies providing polishing additives to improve this problem. Patent CN101671528A provides a polishing liquid for chemical mechanical polishing of single-crystal silicon wafers, which consists of an abrasive, an active agent, a dispersant, a chelating agent, a pH regulator and pure water. The abrasive component included in the technical solution provided by this invention has strict requirements on particle size, increasing the preparation cost of the polishing liquid, and the technical effect of the polishing liquid is not provided, making it difficult to know its actual application effect. Summary of the Invention

[0004] The purpose of the present invention is to provide a single-crystal silicon polishing aid additive and its application. Based on the defects of the prior art, the present invention has developed a polishing aid additive on the basis of research on rough polishing technology. The present invention has proven through rigorous and detailed experiments that the additive provided by the present invention can solve the problems of non-uniform tower base size and excessive step difference between tower bases on the silicon wafer surface.

[0005] To achieve the above object, the technical solution adopted by the present invention is: a single-crystal silicon polishing aid additive, by mass ratio, includes the following components: a co-directional corrosion promoter 0.5%-3.0%, an antifoaming agent 1.0%-5.0%, a cleaning agent 0.5%-2.0%, a non-ionic surfactant 1.0%-6.0%, and the balance is deionized water.

[0006] Specifically, the co-directional etchant is one or a combination of several of polyalcohol, polypropylene glycol, and polyether alcohol; the defoamer is one or a combination of several of polysucrose, trehalose, chitosan oligosaccharide, and β-glucan; the cleaning agent is one or a combination of two of isomeric alcohol oleate and triethanolamine oleate; the non-ionic surfactant is one or a combination of several of polyoxyethylene alkylamine, alkylphenol polyoxyethylene quaternary ammonium salt, fatty alcohol polyoxyethylene ether monoquaternary ammonium salt, and sorbitan monofatty acid ester polyoxyethylene ether quaternary ammonium salt.

[0007] The co-directional etchant promoter in the additive can reduce the corrosion rate difference between the (111) plane of crystalline silicon and other planes; the defoamer helps the generated H2 to quickly detach from the silicon wafer surface during the reaction; the cleaning agent ensures the cleanliness of the silicon wafer surface; the non-ionic surfactant can ensure the dispersibility of the solution, making the corrosion rate of the solution on the entire surface of the silicon wafer uniform, thus obtaining a uniform pyramid base.

[0008] Furthermore, the present invention also provides the application of the above additive in the single-crystal silicon rough polishing reaction. Specifically, the above single-crystal silicon polishing aid additive is mixed with an alkali solution to form a reaction solution for single-crystal silicon wafer rough polishing. Specifically, the alkali solution is a sodium hydroxide solution or a potassium hydroxide solution with a mass concentration of 8% - 12%; the proportion of the single-crystal silicon polishing aid additive in the reaction solution is 0.5% - 1.5%; the reaction temperature is 65 - 85 °C, and the reaction time is 240 - 360 s.

[0009] Compared with the prior art, the present invention has the following beneficial effects or advantages:

[0010] (1) The additive provided by the present invention helps the generated H2 to quickly detach from the silicon wafer surface during the reaction, thus effectively improving the basket marks, effectively inhibiting the generation of pyramid bases on the silicon wafer surface, and the additive of the present invention has simple components, simple process implementation, and outstanding effects.

[0011] (2) The additive provided by the present invention is applied to the single-crystal silicon rough polishing reaction, can effectively control the reaction rate, reduce the corrosion rate difference between the (111) plane of crystalline silicon and other planes, achieve double-sided polishing of the original silicon wafer, make the generated pyramid bases more uniform, and the step difference between the bases is not more than 1.5 μm.

[0012] (3) The additive provided by the present invention is applied to the single-crystal silicon rough polishing reaction, and the obtained silicon wafer surface is flatter, has a higher reflectivity and a lower specific surface area, which is beneficial to the passivation treatment of the silicon wafer surface, thereby improving the efficiency of solar cell wafers. Description of the Drawings

[0013] Figure 1 It is a laser confocal 3D microscope test diagram after the reaction of a silicon wafer without adding an additive in the rough polishing process.

[0014] Figure 2 Laser confocal 3D microscope test chart after the reaction of the silicon wafer with the additive provided by the present invention added to the rough polishing process.

[0015] Figure 3 Laser confocal 3D microscope test chart after the reaction of the silicon wafer with additive 4# added to the rough polishing process.

[0016] Figure 4 Laser confocal 3D microscope test chart after the reaction of the silicon wafer with additive 5# added to the rough polishing process.

[0017] Figure 5 Laser confocal 3D microscope test chart after the reaction of the silicon wafer with additive 6# added to the rough polishing process. Specific embodiments

[0018] Next, the technical solution of the present invention will be described in conjunction with the embodiments. However, the present invention is not limited to the following embodiments.

[0019] In the following embodiments, the experimental methods and detection methods are all conventional methods unless otherwise specified; the medicaments and materials can be obtained on the market unless otherwise specified; the index data are all conventional measurement methods unless otherwise specified.

[0020] Example 1

[0021] This example provides the application of the additive of the present invention in the rough polishing reaction of single crystal silicon.

[0022] 1. Prepare 3 groups of polishing aid additives with different ratios. The specific components and masses are shown in Table 1:

[0023] Table 1 Components and ratios of the additives provided by the present invention

[0024]

[0025] Mix and stir the above 3 groups of additives with different ratios respectively, and label them as 1#, 2#, and 3#, and store them for later use.

[0026] 2. Add the additives prepared in the previous step to the sodium hydroxide solution with a mass percentage of 10% according to a volume percentage of 1% respectively, mix and stir to obtain 3 reaction solutions with different ratios, and store them for later use.

[0027] 3. Set up 4 groups of tests, 1 control group and 3 experimental groups. The control group does not add additives. In the experimental groups, the original silicon wafers are placed in a flower basket container in units of 400 pieces each, and then the whole flower basket is placed in the reaction solutions obtained in the previous step respectively for double-sided polishing. The reaction temperature is 75 °C and the reaction time is 300S.

[0028] 4. The SEM test images of the silicon wafers after the reaction without additives in the rough polishing process are as Figure 1 shown, and the SEM test images of the silicon wafers after the reaction with this additive in the rough polishing process are as Figure 2 shown.

[0029] From Figure 1 and Figure 2 comparison, it can be seen that after adding this additive in the rough polishing process, the pyramid bases of the silicon wafers are more uniform, the step difference between the bases is smaller, and the surface of the silicon wafers is also flatter. Comparing with Example 2

[0030] This example provides the application of the additive of the present invention after replacing some components in the rough polishing reaction of single crystal silicon.

[0031] 1. Configure 3 groups of polishing aid additives with different components and ratios. The specific components and masses are shown in Table 2:

[0032] Table 2 Component and ratio of the additive in the comparative test

[0033]

[0034]

[0035] Mix and stir the above 3 groups of additives with different components and ratios respectively, mark them as 4#, 5#, and 6#, and store them for later use.

[0036] 2. Add the additives prepared in the previous step into the sodium hydroxide solution with a mass percentage of 10% according to a volume percentage of 1% respectively, mix and stir to obtain 3 reaction solutions with different components and ratios, and store them for later use.

[0037] 3. Set up 3 groups of tests. Put the original silicon wafers into the flower basket container in units of 400 pieces each, and then put the whole flower basket into the reaction solutions obtained in the previous step respectively for double-sided polishing. The reaction temperature is 75 °C and the reaction time is 300 s.

[0038] 4. The SEM test images of the silicon wafers after the reaction with additive 4# in the rough polishing process are as Figure 3 shown, the SEM test images of the silicon wafers after the reaction with additive 5# in the rough polishing process are as Figure 4 shown, and the SEM test images of the silicon wafers after the reaction with additive 6# in the rough polishing process are as Figure 5 shown.

[0039] The results show that Figure 3 , Figure 4 , Figure 5Compared with the control group, the silicon wafers in [description] have more uniform pyramid bases of the silicon wafers, smaller step differences between the bases, and a flatter surface of the silicon wafers; however Figure 2 The obtained silicon wafers and Figure 3 , Figure 4 , Figure 5 compared, the silicon wafers have more uniform pyramid bases, smaller step differences between the bases, and a flatter surface. This shows that the additive formulation provided by the present invention has irreplaceable and indispensable components.

[0040] As described above, the present invention can be preferably implemented. The above embodiments are only descriptions of the preferred implementation modes of the present invention, and do not limit the scope of the present invention. Without departing from the design spirit of the present invention, various changes and improvements made by those of ordinary skill in the art to the technical solutions of the present invention shall fall within the protection scope determined by the present invention.

Claims

1. A single-crystalline silicon assisted polishing additive, characterized in that, Composed of the following components by mass ratio: polyhydric alcohol 0.5%-3.0%, oligo-chitosan 1.0%-5.0%, isomeric alcohol oleic acid soap 0.5%-2.0%, polyoxyethylene alkylamine 1.0%-6.0%, and the balance being deionized water.

2. Use of the additive according to claim 1 in the single-crystal silicon rough polishing reaction, characterized in that, Mix the single-crystal silicon auxiliary polishing additive with an alkaline solution to serve as the reaction solution for rough polishing of single-crystal silicon wafers.

3. The application according to claim 2, characterized in that, The alkaline solution is a sodium hydroxide solution or a potassium hydroxide solution with a mass concentration of 8%-12%.

4. The application according to claim 3, wherein By mass ratio, the proportion of the single-crystal silicon auxiliary polishing additive in the reaction solution is 0.5%-1.5%.

5. The application according to claim 4, wherein The reaction temperature is 65-85°C, and the reaction time is 240-360 s.

Images