Chemical dry etching of platinum using Cl-2/CO gas mixture

Abstract

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 degrees C, which corresponds to the sublimation temperature of platinum dicarbonyl chloride, PtCl2(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 degrees 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 SiO2 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 degrees C.