Cleaning method

A cleaning method for removing an adhesive residue remaining on a debonded substrate, the method comprising:

• removing an adhesive residue remaining on the debonded semiconductor substrate with a cleaning agent composition;
• wherein the cleaning agent composition comprises:
• a tetrahydrocarbylammonium fluoride,
• an organic solvent comprising a lactam compound represented by formula (1):
• where R101 represents a C1 to C6 alkyl group;
• and R102 represents a C1 to C6 alkylene group, and
• a ring-structure-having ether compound including at least one species selected from among a cyclic ether compound, a cycloalkyl (chain alkyl) ether compound, a cycloalkyl (branched alkyl) ether compound, and a di(cycloalkly) ether compound.