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WO-2026092402-A1 - PREPARATION METHOD FOR SEMICONDUCTOR SUBSTRATE, AND SOLAR CELL

WO2026092402A1WO 2026092402 A1WO2026092402 A1WO 2026092402A1WO-2026092402-A1

Abstract

The present invention provides a preparation method for a semiconductor substrate, and a solar cell. The preparation method comprises the following steps: 1) performing a metal chemical etching treatment and a metal particle cleaning treatment on a pre-treated silicon wafer, so as to obtain a semi-finished silicon wafer; 2) performing a primary surface modification treatment on the semi-finished silicon wafer by using a primary surface modification liquid, so as to obtain a primary silicon wafer; and 3) performing a secondary surface modification treatment on the primary silicon wafer by using a secondary surface modification liquid, so as to obtain a semiconductor substrate, wherein the primary surface modification liquid comprises hydrofluoric acid and a strong oxidant, and the secondary surface modification liquid comprises an alkali solution. By means of the preparation method, the step height difference at a line mark on the surface of the silicon wafer can be reduced, and the prepared semiconductor substrate has a relatively high surface reflectivity; and when the semiconductor substrate is used in a solar cell, the efficiency of the cell can be improved.

Inventors

  • LI, CHENG
  • PENG, Changtao
  • XIN, Ke
  • XIAO, Jihong
  • LU, Shilong

Assignees

  • 安徽华晟新能源科技股份有限公司

Dates

Publication Date
20260507
Application Date
20251027
Priority Date
20241029

Claims (11)

  1. A method for preparing a semiconductor substrate, characterized by comprising the following steps: Step 1) Perform metal chemical etching and metal particle cleaning on the pretreated silicon wafer to obtain a semi-finished silicon wafer; Step 2) The semi-finished silicon wafer is subjected to a primary surface modification treatment using a primary surface modification solution to obtain a primary silicon wafer; the primary surface modification solution includes hydrofluoric acid and a strong oxidizing agent; Step 3) The primary silicon wafer is subjected to secondary surface modification treatment using a secondary surface modification liquid to obtain the semiconductor substrate; the secondary surface modification liquid includes an alkaline solution; the step height difference at the line marks on the surface of the semiconductor substrate does not exceed 0.15 μm.
  2. According to the preparation method of claim 1, the metal chemical etching process comprises: The pretreated silicon wafer is immersed in a first metal chemical etching solution containing metal salt, first oxidant and hydrofluoric acid at 25-50°C for 20-240 seconds to obtain an intermediate silicon wafer.
  3. According to the preparation method of claim 2, the metal salt is characterized in that it contains ions of at least one metal selected from Pt, Au, Ag, Cu, and Ni, and the molar concentration of the metal salt in the first metal chemical etching solution is 0.5–10 M; and/or, The first oxidant is at least one selected from H₂O₂ , HNO₃ , and KMnO₄ , and the molar concentration of the first oxidant in the first metal chemical etching solution is 5–20 M; and/or, In the first metal chemical etching solution, the molar concentration of hydrofluoric acid is 1 to 10 M.
  4. According to the preparation method of claim 1, the metal chemical etching process comprises: The pretreated silicon wafer is subjected to metal deposition to obtain a metal-attached silicon wafer, wherein the thickness of the attached metal layer in the metal-attached silicon wafer is 1 to 10 nm. The silicon wafer with attached metal is immersed in a second metal chemical etching solution containing hydrofluoric acid and a second oxidant at 25–50°C for 20–240 seconds to obtain an intermediate silicon wafer.
  5. According to the preparation method of claim 4, the attached metal layer is obtained by performing the metal deposition treatment on at least one metal selected from Pt, Au, Ag, Cu, and Ni; and/or, In the second metal chemical etching solution, the molar concentration of the hydrofluoric acid is 1–10 M; and/or, The second oxidant is at least one of H₂O₂ , HNO₃ , and KMnO₄ , and the molar concentration of the second oxidant in the second metal chemical etching solution is 1–20 M.
  6. The preparation method according to any one of claims 2 to 5 is characterized in that the metal particle cleaning treatment includes: immersing the intermediate silicon wafer in a metal cleaning agent at 20 to 25°C for 3 to 10 minutes to obtain the semi-finished silicon wafer; in, The metal cleaning agent comprises a mixed solution of HCl, H₂O₂ , and H₂O , wherein the molar concentration ratio of HCl, H₂O₂ , and H₂O in the mixed solution is (1–3):(1–3):(3–8); or, The metal cleaning agent includes nitric acid, wherein the nitric acid has a mass fraction of 30–50 wt%; or, The metal cleaning agent includes aqua regia; or, The metal cleaning agent includes ammonia water, wherein the mass fraction of the ammonia water is 5-25 wt%.
  7. The preparation method according to any one of claims 1 to 6 is characterized in that, in the primary surface modification solution, the molar concentration of hydrofluoric acid is 0.1 to 5 M; and/or, The strong oxidant in the primary surface modification solution is at least one selected from nitric acid, concentrated sulfuric acid, and KMnO4 ; the molar concentration of the strong oxidant in the primary surface modification solution is 0.1–5 M; and/or, The surface modification treatment is carried out at a temperature of 20–30°C for 30–120 seconds.
  8. The preparation method according to any one of claims 1 to 7 is characterized in that the alkali in the alkaline solution includes at least one selected from KOH, NaOH, and tetramethylammonium hydroxide, and the mass fraction of the alkaline solution is 5-30 wt%; and/or, The secondary surface modification treatment is carried out at a temperature of 45–60°C for 10–60 seconds.
  9. The preparation method according to any one of claims 1 to 8 is characterized in that the preparation method further includes: after step 3), the semiconductor substrate is cleaned, the cleaning process including cleaning the semiconductor substrate sequentially with a mixed solution of alkali and hydrogen peroxide, a mixed solution of hydrochloric acid and hydrogen peroxide, and a hydrofluoric acid solution; or, The preparation method further includes: after step 3), texturing the semiconductor substrate.
  10. A solar cell includes a semiconductor substrate prepared by the preparation method according to any one of claims 1 to 9; An intrinsic passivation layer, a doped layer, a transparent conductive layer, and a metal electrode are deposited sequentially on both sides of the semiconductor substrate.
  11. The solar cell according to claim 10 is characterized in that one side surface of the semiconductor substrate is textured and the other side is polished.

Description

Semiconductor substrate fabrication methods and solar cells Cross-reference of related applications This application claims priority to Chinese patent application No. 202411522993.9, filed on October 29, 2024, the entire contents of which are incorporated herein by reference. Technical Field This invention relates to a method for preparing a semiconductor substrate and a solar cell, belonging to the field of crystalline silicon processing technology. Background Technology In the semiconductor and solar photovoltaic industries, dicing silicon rods into wafers is a crucial process, as the quality of the wafers directly impacts subsequent manufacturing and processing. Line marks left on the wafer surface after dicing are a significant factor affecting surface quality. Even after deposition processes such as transparent conductive films, the step height difference caused by these line marks can still affect the grid line printing quality, leading to grid breakage. Furthermore, line marks can also affect passivation performance, increasing the cell's load. Additionally, the back of solar cells typically uses a polished surface to improve long-wave absorption. The flatness of this polished surface affects light reflection, and the presence of line marks reduces the reflectivity of the polished back surface, thus impacting the cell's conversion efficiency. Currently, the semiconductor industry has high requirements for the surface quality of silicon wafers. The main method for removing line marks is chemical polishing, but this method requires specialized equipment and polishing slurry, making it costly. The silicon wafers used in the photovoltaic industry are very thin, and chemical polishing would cause excessive loss to the already thin wafers, leading to defects. Currently, the photovoltaic industry generally uses high-concentration alkaline solutions for isotropic polishing to improve the surface quality of silicon wafers, but this method cannot completely eliminate line marks; wafers treated with this method still have a step height difference of 2-4 micrometers. Therefore, how to prepare a semiconductor substrate with high surface flatness is an urgent problem to be solved. Summary of the Invention To address the aforementioned deficiencies, this invention provides a method for preparing a semiconductor substrate and a solar cell. After processing the diced silicon wafer using this method, the weight of the silicon wafer does not decrease significantly, and the step height difference at the line marks on the silicon wafer surface does not exceed 0.15 μm, thus significantly eliminating the line marks on the silicon wafer surface. Furthermore, this method has a simple preparation process and is easy to mass-produce. The present invention provides a semiconductor substrate, which is prepared by the above-described method for preparing a semiconductor substrate. The semiconductor substrate has a high surface flatness, which can meet the needs of the photovoltaic industry, which has high requirements for the flatness of silicon wafers. This invention provides a solar cell comprising a semiconductor substrate as described above as a back reflective layer, or a texturing process using the semiconductor substrate as described above. The back reflective layer of the silicon wafer in this solar cell has a high reflectivity, which can reflect unabsorbed light back to the active layer, thereby improving light absorption efficiency and thus enhancing the performance of the solar cell. Texturing using the semiconductor substrate as described above can provide a more uniform texture, thereby improving the efficiency of the solar cell. One aspect of the present invention provides a method for preparing a semiconductor substrate, the method comprising the following steps: Step 1) Perform metal chemical etching and metal particle cleaning on the pretreated silicon wafer to obtain a semi-finished silicon wafer; Step 2) The semi-finished silicon wafer is subjected to a primary surface modification treatment using a primary surface modification solution to obtain a primary silicon wafer; the primary surface modification solution includes hydrofluoric acid and a strong oxidizing agent; Step 3) The primary silicon wafer is subjected to secondary surface modification treatment using a secondary surface modification liquid to obtain the semiconductor substrate; the secondary surface modification liquid includes an alkaline solution; the step height difference at the line marks on the surface of the semiconductor substrate does not exceed 0.15 μm. The preparation method described above, wherein the metal chemical etching process includes: The pretreated silicon wafer is immersed in a first metal chemical etching solution containing metal salt, first oxidant and hydrofluoric acid at 25-50°C for 20-240 seconds to obtain an intermediate silicon wafer. In the preparation method described above, the metal salt is a salt containing ions o