Method for Cleaning Wafer, and Chemical Used in Such Cleaning Method

A method for cleaning a wafer having a fine uneven surface pattern that at least partially contains a silicon element using a wafer cleaning device that includes a vinyl chloride resin as a liquid contacting member,

• the method comprising retaining a water-repellent protective film-forming chemical in at least a recessed portion of the uneven pattern to form a water-repellent protective film on a surface of the recessed portion,
• the water-repellent protective film-forming chemical comprising:
• a monoalkoxysilane represented by the following general formula [1];
• a sulfonic acid represented by the following general formula [2];
• and
• a diluting solvent,
• wherein the diluting solvent contains 80 to 100 mass % of alcohol with respect to the total 100 mass % of the diluting solvent,
• (R1)aSi(H)3-a(OR2) [1],
• wherein R1 each independently represent at least one selected from monovalent hydrocarbon groups having 1 to 18 carbon atoms in which hydrogen elements may partially or totally be replaced with a fluorine element, R2 represents a monovalent hydrocarbon group having 1 to 18 carbon atoms in which hydrogen elements may partially or totally be replaced with a fluorine element, and a is an integer of 1 to 3,
• R3—S(═O)2OH [2],
• wherein R3 represents a group selected from the group containing a monovalent hydrocarbon group having 1 to 8 carbon atoms in which hydrogen elements may partially or totally be replaced with a fluorine element, and a hydroxyl group.