A method of forming damascene interconnect structure in an organo-silicate glass layer without causing damage to the organo-silicate glass material. The method includes forming a stack of hardmask layers over the organo-silicate glass layer, defining openings in the hardmask and organo-silicate glass layers using a combination of plasma etch and plasma photoresist removal processes and performing one or more additional plasma etch processes that do not include oxygen containing species to etch the openings to depths required for forming the damascene interconnect structures and to remove any organo-silicate material damaged by the combination of plasma etch and plasma photoresist removal processes.