Anomalous etching residues of sputter-deposited Ta upon reactive ion etching using chlorine-based plasmas

Anomalous etching of Ta which is sputter-deposited on silicon carbide (SiC) films is observed upon reactive ion etching (RIE) using a gas mixture of chlorine and chloroform. We find that α-Ta is hardly etched off by either chlorine-based plasmas or aqueous hydrofluoric acids (HF), while β-Ta is easily etched off by the same methods. The extent of α-Ta depends on the surface treatment of SiC. The difference in chemical reactivity between the α phase and β phase is discussed using photoemission spectroscopy.