Chemical Dry Etching of Platinum Using Cl2/CO Gas Mixture

In this study, we have developed a novel method for Pt etching using a chemical dry etching (CDE) system. A volatile etching product was formed during the reaction of Pt with Cl 2 and CO. The etch rate was abruptly increased above 210 °C, which corresponds to the sublimation temperature of platinum dicarbonyl chloride, PtCl 2 (CO) 2 . The maximum etch rate was obtained at the Cl 2 /CO mole ratio of 1/2, which agrees with the stoichiometric ratio of Cl 2 to CO to form platinum dicarbonyl chloride. The large enhancement in etch rate above 210 °C might be attributed to the formation of a volatile platinum carbonyl compound on the Pt surface. A relatively high etch rate above 100 nm/min and high selectivity toward Pt against sublayers such as SiO 2 and TiN were obtained under various etching conditions. Chemical analysis of the etched surface with XPS showed that surface Pt atoms were converted to a volatile compound. XPS and SEM studies of the Pt surface treated with Cl 2 and/or CO indicated that volatile platinum carbonyl compounds were formed in the reaction of CO with Pt surface pretreated with Cl 2 above 210 °C.