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 alpha-Ta is hardly etched off by either chlorine-based plasmas or aqueous hydrofluoric acids (HF), while beta-Ta is easily etched off by the same methods. The extent of alpha-Ta depends on the surface treatment of SiC. The difference in chemical reactivity between the alpha phase and beta phase is discussed using photoemission spectroscopy.