Back polishing method for improving Poly silicon winding plating of TOPCon battery

Abstract

The invention discloses a back surface polishing method for improving Poly silicon winding plating of a TOPCon battery. The back surface polishing method comprises the following steps: removing borosilicate glass on the back surface and the side edge of a diffused silicon wafer; washing with water; drying with an air knife; loading into a special basket for alkaline polishing, and pre-treating in an alkaline polishing machine; washing with water; alkali polishing; washing with water; alkali washing; washing with water; pickling; washing with water; pre-dehydrating the silicon wafer in a slow lifting mode; and drying. According to the method, a circle of nanoscale suede with the width of 1-5 cm grows on the edge of the polished surface by adding the specific additive into the polishing tank, and the nanoscale suede is used for increasing the growth speed of the tunneling oxide layer and the Poly silicon on the edge of the polished surface in the growth process of the tunneling oxide layer and the Poly silicon, so that the condition of boron surface expansion winding plating is reduced, and the service life of the polishing surface is prolonged. And the difficulty of removing the boron, expanding the surface and plating is reduced.

Description

Technical Field

[0001] This invention relates to the field of alkaline polishing and cleaning technology for solar cells, and more particularly to a method for improving the back-side polishing of TOPCon cells with poly silicon winding plating. Background Technology

[0002] With societal development, cost reduction and efficiency improvement have become two unavoidable topics for photovoltaic cells. TOPCon cells, as one of the photovoltaic energy sources with the highest mass production conversion efficiency and greatest potential, inevitably encounter boron-enlarged surface coating during the core processes of tunneling layer and polycrystalline silicon growth. Currently, during the cleaning and coating process, incomplete or excessive cleaning frequently occurs, causing localized damage to the poly surface, thereby reducing cell conversion efficiency and yield. Summary of the Invention

[0003] Based on the technical problems existing in the background art, the present invention proposes an improved back polishing method for TOPCon battery Poly silicon winding plating.

[0004] This invention proposes an improved back-side polishing method for TOPCon battery polysilicon winding plating, comprising the following steps: S1. Removal of borosilicate glass from the back and sides of the silicon wafer after diffusion: Using high-concentration hydrofluoric acid, the borosilicate glass layer on the back and sides of the silicon wafer is removed on a chain machine under the protection of a water film on the front side. S2. Water washing: Rinse the front and back of the water jet with room temperature water jet to remove any hydrofluoric acid residue; S3. Air knife drying: Use a hot air knife to dry any water residue on the surface of the silicon wafer; S4. Load the special basket for alkaline polishing and put it into the alkaline polishing machine for pretreatment: use a low concentration of potassium hydroxide and hydrogen peroxide mixture to remove organic residues on the surface; S5. Water washing: Use overflow water to wash the mixture brought from the pretreatment tank; S6. Alkaline polishing: A mixture of high-concentration potassium hydroxide and alkaline polishing additives is used for back polishing, while a nano-layer textured surface is grown at the edge of the back. S7. Water washing: Use overflow water to wash the mixture brought from the polishing tank; S8. Alkaline washing: Use a low-concentration mixture of potassium hydroxide and hydrogen peroxide to remove organic residues from the surface; S9. Water washing: Use overflow water to further remove organic residues from the surface; S10. Pickling: High-concentration hydrofluoric acid and low-concentration hydrochloric acid are used to remove borosilicate glass and metal ions from the surface of the silicon wafer; S11. Water washing: Use a mixture of overflow water and hydrogen peroxide to further remove organic residues from the surface; S12. Slow lifting: Immerse the silicon wafer in a continuously overflowing pure water bath for 20-100 seconds, and use a slow lifting method to pre-dehydrate it; S13. Drying: Use high temperature to thoroughly dry the silicon wafer.

[0005] Preferably, the concentration of hydrofluoric acid in step S1 is 8-10%.

[0006] Preferably, the air knife drying in step S3 uses hot air at 40-60℃.

[0007] Preferably, in step S4, the concentration of potassium hydroxide is 0.3-5%, the concentration of hydrogen peroxide mixture is 0.5-5%, and the silicon wafer is immersed at 20-60°C for 20-200 seconds to remove residual organic matter on the silicon wafer.

[0008] Preferably, the water washing temperature in steps S5 and S7 is room temperature, and the time is 20-200 seconds.

[0009] Preferably, in step S6 alkaline polishing, the concentration of potassium hydroxide is 1-10%, the concentration of alkaline polishing additive is 0.5-10%, and the back side is polished by immersion at 40-80℃. The width of the nano-textured surface generated at the edge of the back side is 0.5-5µm, and the cleaning time is 200s.

[0010] Preferably, in step S8, the concentration of potassium hydroxide used for alkaline washing is 0.1-10%, the concentration of hydrogen peroxide mixture is 0.1-15%, and the silicon wafer is immersed at 20-60°C for 20-200 seconds to further remove additive residues.

[0011] Preferably, the water washing temperature in steps S9 and S11 is room temperature, and the time is 20-200 seconds.

[0012] Preferably, in the pickling step S10, the concentration of hydrofluoric acid is 1-10% and the concentration of hydrochloric acid is 1-20%.

[0013] Preferably, in step S12, the drying process involves drying in a drying tank at 80-110°C for 500-800 seconds to complete the dehydration.

[0014] In this invention, the back polishing method for improving the polysilicon wrapping of TOPCon batteries involves adding specific additives to the polishing tank to grow a 1-5cm wide nanoscale textured surface around the edge of the polished surface. This enhances the growth rate of the tunneling oxide layer and polysilicon at the edge of the polished surface during the growth process, thereby reducing the need for boron wrapping and simplifying the removal of boron wrapping. Attached Figure Description

[0015] Figure 1This is a schematic diagram of the structure of an improved back-side polishing method for Poly silicon winding plating of TOPCon batteries proposed in this invention; Figure 2 This is a schematic flowchart of an improved back-side polishing method for Poly silicon winding plating of TOPCon batteries proposed in this invention. Implementation

[0016] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0017] Reference Figure 1-2 A method for improving the back-side polishing of TOPCon battery polysilicon winding plating includes the following steps: S1. Removal of borosilicate glass from the back and sides of the diffused silicon wafer: The borosilicate glass layer on the back after diffusion is removed using 8-10% concentration room temperature hydrofluoric acid on a chain machine. S2. Water washing: Rinse the front and back of the water jet with room temperature water jet to remove any hydrofluoric acid residue; S3. Air knife drying: Use a 40-60℃ hot air knife to dry any water residue on the surface of the silicon wafer; S4. Load the special basket for alkaline polishing and put it into the alkaline polishing machine for pretreatment: immerse in a mixture of 0.3-5% potassium hydroxide and 0.5-5% hydrogen peroxide at 20-60℃ for 20-200 seconds to remove organic residues on the silicon wafer. S5. Water washing: Use overflow water to wash the mixture brought from the pretreatment tank at room temperature for 20-200 seconds. S6. Alkaline polishing: 1-10% potassium hydroxide and 0.5-10% alkaline polishing additive, soaked at 40-80℃ for polishing the back side, and a 0.5-5um wide nano-textured surface is generated at the edge of the back side. S7. Water washing: Use overflow water to wash the mixture brought from the polishing tank at room temperature for 20-200 seconds. S8. Alkaline washing: Immerse in a mixture of 0.1-10% potassium hydroxide and 0.1-15% hydrogen peroxide at 20-60℃ for 20-200 seconds to further remove additive residues on the silicon wafer; S9. Water washing: Use overflow water to wash the mixture brought from the polishing tank at room temperature for 20-200 seconds. S10. Pickling: 1-10% hydrofluoric acid and 1-20% hydrochloric acid remove borosilicate glass and metal ions from the surface of the silicon wafer; S11. Water washing: Use overflow water to wash the mixture brought from the polishing tank at room temperature for 20-200 seconds. S12. Slow lift: Soak in a continuously overflowing pure water tank for 20-100 seconds, then slowly lift and further dehydrate; S13. Drying: The product is dried in a drying tank at 80-110℃ for 500-800 seconds to complete the dehydration.

[0018] This invention removes the borosilicate glass from the back side 4 and sides of the diffused silicon wafer 2: using high-concentration hydrofluoric acid, the borosilicate glass layer on the back side 4 and sides of the silicon wafer is removed on a chain machine under the protection of a water film on the front side; the hydrofluoric acid residue on the front and back sides is rinsed with a room-temperature water jet; and the water residue on the surface of the silicon wafer 2 is dried with a hot air knife. Place the wafer in a special alkaline polishing basket and pre-treat it in the alkaline polishing machine: Use a low-concentration potassium hydroxide and hydrogen peroxide mixture to remove organic residues from surface 1; use overflow water to rinse the mixture from the pre-treatment tank; use a high-concentration potassium hydroxide and alkaline polishing additive mixture for backside 4 polishing, while simultaneously growing a nano-layer textured surface 3 around the backside edge; use overflow water to rinse the mixture from the polishing tank; use a low-concentration potassium hydroxide and hydrogen peroxide mixture to remove organic residues from the surface; use overflow water to further remove organic residues from the surface; use high-concentration hydrofluoric acid and low-concentration hydrochloric acid to remove borosilicate glass and metal ions from the silicon wafer surface; use overflow water and hydrogen peroxide mixture to further remove organic residues from the surface; immerse the wafer in a continuously overflowing pure water tank for 20-100 seconds, and use a slow lifting method to pre-dehydrate the silicon wafer; use high temperature to thoroughly dry the silicon wafer.

[0019] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for improving the back-side polishing of TOPCon battery polysilicon winding plating, characterized in that, Includes the following steps: S1. Removal of borosilicate glass from the back and sides of the silicon wafer after diffusion: Using high-concentration hydrofluoric acid, the borosilicate glass layer on the back and sides of the silicon wafer is removed on a chain machine under the protection of a water film on the front side. S2. Water washing: Rinse the front and back for hydrofluoric acid residue using a water jet at room temperature; S3. Air knife drying: Use a hot air knife to dry any water residue on the surface of the silicon wafer; S4. Load the special basket for alkaline polishing and put it into the alkaline polishing machine for pretreatment: use a low concentration of potassium hydroxide and hydrogen peroxide mixture to remove organic residues on the surface; S5. Water washing: Use overflow water to wash the mixture brought from the pretreatment tank; S6. Alkaline polishing: A mixture of high-concentration potassium hydroxide and alkaline polishing additives is used for back polishing, while a nano-layer textured surface is grown at the edge of the back. S7. Water washing: Use overflow water to wash the mixture brought from the polishing tank; S8. Alkaline washing: Use a low-concentration mixture of potassium hydroxide and hydrogen peroxide to remove organic residues from the surface; S9. Water washing: Use overflow water to further remove organic residues from the surface; S10. Pickling: High-concentration hydrofluoric acid and low-concentration hydrochloric acid are used to remove borosilicate glass and metal ions from the surface of the silicon wafer; S11. Water washing: Use a mixture of overflow water and hydrogen peroxide to further remove organic residues from the surface; S12. Slow lifting: Immerse the silicon wafer in a continuously overflowing pure water bath for 20-100 seconds, and use a slow lifting method to pre-dehydrate it; S13. Drying: Use high temperature to thoroughly dry the silicon wafer.

2. The method for improving the back-side polishing of TOPCon battery Poly silicon winding plating according to claim 1, characterized in that, The concentration of hydrofluoric acid in step S1 is 8-10%.

3. The method for improving the back-side polishing of TOPCon battery Poly silicon winding plating according to claim 1, characterized in that, In step S3, the air knife is used to dry the product using hot air at 40-60℃.

4. The method for improving the back-side polishing of TOPCon battery Poly silicon winding plating according to claim 1, characterized in that, In step S4, the concentration of potassium hydroxide is 0.3-5%, the concentration of hydrogen peroxide mixture is 0.5-5%, and the silicon wafer is immersed at 20-60℃ for 20-200 seconds to remove residual organic matter on the silicon wafer.

5. The method for improving the back-side polishing of TOPCon battery Poly silicon winding plating according to claim 1, characterized in that, The water washing in steps S5 and S7 is performed at room temperature for 20-200 seconds.

6. The method for improving the back-side polishing of TOPCon battery Poly silicon winding plating according to claim 1, characterized in that, In step S6, the concentration of potassium hydroxide in alkaline polishing is 1-10%, the concentration of alkaline polishing additive is 0.5-10%, and it is immersed at 40-80℃ for polishing the back side. The width of the nano-textured surface generated at the edge of the back side is 0.5-5um, and the cleaning time is 200s.

7. The method for improving the back-side polishing of TOPCon battery Poly silicon winding plating according to claim 1, characterized in that, In step S8, the concentration of potassium hydroxide for alkaline washing is 0.1-10%, and the concentration of hydrogen peroxide mixture is 0.1-15%. The wafer is then immersed at 20-60°C for 20-200 seconds to further remove any additive residues.

8. The method for improving the back-side polishing of TOPCon battery Poly silicon winding plating according to claim 1, characterized in that, The water washing temperature in steps S9 and S11 is room temperature, and the time is 20-200 seconds.

9. The method for improving the back-side polishing of TOPCon battery Poly silicon winding plating according to claim 1, characterized in that, In the pickling step S10, the concentration of hydrofluoric acid is 1-10% and the concentration of hydrochloric acid is 1-20%.

10. The method for improving the back-side polishing of TOPCon battery Poly silicon winding plating according to claim 1, characterized in that, In step S12, the drying process involves drying in a drying tank at 80-110°C for 500-800 seconds to complete the dehydration.

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