Deep-ultraviolet (DUV) lithography is the preferred technique for high-resolution patterning at sub-180 nm technology nodes. The via first (VF) dual-damascene (DD) process is the most commonly used integration scheme for realizing the copper interconnects. A major problem encountered with the use of the DUV photoresist in the VFDD process is the presence of resist residues, also known as resist contamination or resist poisoning, which are difficult to remove after trench lithography. In this study, the causes of the DUV-resist contamination for a low-k organosilicate SiOC:H dielectric have been investigated. The effects of different types of underlying substrates and processes used for forming the DD structures on the resist contamination are studied and the physical mechanisms responsible for formation of resist residues are identified. The post via-etching solvent cleaning process is identified as a major contributor to resist contamination and solutions are proposed to minimize DD-process-induced DUV-resist contamination. (C) 2004 American Vacuum Society.