Inductively coupled plasma reactive ion etching of copper thin films patterned with SiO2 masks was carried out using CH3COOH/Ar gas. The etch rate, etch selectivity to SiO2 mask, and the etch profiles of copper films were examined. The evolution study of the etch profile as a function of gas concentration and etch depth revealed the etch sequence and etch mechanism. In the optimized CH3COOH/Ar gas, the systematic approach on the etch characteristics of copper films was performed by changing the etch parameters including inductively coupled plasma (ICP) rf power, dc-bias voltage to substrate, and process pressure. As the ICP rf power and dc-bias voltage increased and the process pressure decreased, the etch rate increased and the etch profile improved. X-ray photoelectron spectroscopy was used to determine the etch mechanism in CH3COOH/Ar gas. Finally, the etching of copper films in the CH3COOH/Ar was achieved with good etch profile with a high degree of anisotropy.