Patent ID: 8158568

Claim:
A cleaning liquid used in a process for forming a dual damascene structure comprising steps of etching a low dielectric layer accumulated on a substrate having thereon a metallic layer to form a first etched-space; charging a sacrifice layer in the first etched-space; partially etching the low dielectric layer and the sacrifice layer to form a second etched-space connected to the first etched-space; and removing the sacrifice layer remaining in the first etched-space with the cleaning liquid, wherein the cleaning liquid comprises (a) 1-25 mass % of a quaternary ammonium hydroxide represented by the following general formula (I), (b) 30-70 mass % of a water soluble organic solvent, (c) 20-60 mass % of water, and (d) a mercapto group-containing compound: wherein R 1 , R 2 , R 3 and R 4 each independently represents an alkyl group having 1-4 carbon atoms or a hydroxyalkyl group having 1-4 carbon atoms.