Alkali polishing diffusion method for improving sheet resistance uniformity of large-size furnace diameter

The invention relates to an alkali polishing diffusion method for improving sheet resistance uniformity of a large-size furnace diameter. The alkali polishing diffusion method comprises the following steps: step 1, placing a process silicon wafer in a process furnace tube for pretreatment; step 2; uniformly depositing a silicon dioxide layer along the surface of the silicon wafer; a third step; depositing a phosphorus source layer with gradient concentration along the surface of the silicon dioxide layer; step 4; and the phosphorus source layer is diffused into the silicon wafer after being subjected to cooling oxidation treatment. The method has the advantages that on the basis of an existing large-size furnace diameter, the uniformity of sheet resistance is improved, meanwhile, a shallow PN junction with low concentration and uniform distribution in a high-concentration junction area on the surface can be obtained through an alkali polishing diffusion method, and then the conversion efficiency of a battery