Secondary cleaning

Purpose: To remove the PN junction at the edge of the wafer to prevent short circuits and to remove the phosphosilicate glass (PSG) formed after diffusion.

The method comprises the steps of: floating the silicon wafer above the chemical agent, oxidizing the elemental silicon on the surface by the strong oxidative oxidation of nitric acid, and then reacting with the hydrofluoric acid to form silicon fluoride dissolved in water, thereby achieving the purpose of removing the edge of the silicon wafer. .