The effects of CO addition to platinum etching process using Cl-2 plasma were investigated. X-ray photoelectron spectroscopy (XPS) was used to determine the chemical binding state of the Pt surface treated with Cl-2 plasma and CO. After CO treatment on the Pt pre-exposed to Cl-2 plasma was carried out sequentially at 240 degrees C, the ratio of Pt metal component, Pt(0), was increased significantly. The platinum chloride compounds on the Pt surface were removed vigorously by CO treatment at 240 degrees C, which is above the sublimation temperature of Pt(CO)(2)Cl-2, i.e., 210 degrees C. The scanning electron microscopy (SEM) and atomic force microscopy (AFM) results of the treated Pt film surfaces indicated that the volatile etching of Pt using Cl-2/CO mixed gas plasma proceeded via the sublimation of Pt chloride compounds by means of CO.