Akihiro Kojima,(a)) Takayuki Sakai, and Tokuhisa Ohiwa Process & Manufacturing Engineering Center Semiconductor Company, Toshiba Corp. 8, Shinsugha-cho, Isogo-ku, Yokohama 235-8522, Japan (Received 19 February 2004: accepted 30 August 2004; published 4 November 2004) Because Cu is easily oxidized and its oxidation reaction proceeds without stopping, the oxygen ashing process causes unacceptable oxidation of the Cu surface. We, investigated the chemical state and morphology of the Cu surface after the oxygen ashing process using x-ray photoelectron spectroscopy/Auger electron spectroscopy and scanning electron microscopy, and then considered the oxidation mechanism of the Cu surface under the oxygen downstream and the oxygen reactive ion etch (RIE) ashing processes in the substrate temperature range of 35 degreesC to 260 degreesC. The Cu surface treated by an oxygen RIE ashing process at temperatures below 150 degreesC was found to have chiefly CuO bonds, whereas the Cu surface treated by the oxygen downstream ashing process consisted mostly of CuO bonds. The oxidized Cu thickness after the oxygen downstream process was thicker than that formed by the oxygen RIE ashing process. The Cu surface treated with the oxygen RIE ashing process at under 150 degreesC is less prone to oxidization because the Cu surface with CuO formation has a smooth surface that suppresses further oxidation. (C) 2004 American Vacuum Society.