Patent ID: 7442652

Claim:
A method for removing contamination adhering to a silicon substrate rear and end faces, the contamination containing at least one element selected from zirconium (Zr) and hafnium (Hf) and wherein the contamination includes the at least one element bonded with silicon (Si), the method comprising: a first process of wet processing the silicon substrate by a first remover liquid that contains hydrofluoric acid, the hydrofluoric acid being a concentration equal to or greater than 30 mass %; and a second process of wet processing the silicon substrate by a second remover liquid that contains oxidizing reagent and one of hydrofluoric acid and salt of hydrofluoric acid; a third process of wet processing the silicon substrate, after the second process, by a third remover liquid that contains one of hydrofluoric acid and salt of hydrofluoric acid; and a fourth process of wet processing the silicon substrate by a fourth remover liquid that contains oxidizing reagent and one of hydrofluoric acid and salt of hydrofluoric acid.