Growth mechanism difference of sputtered HfO2 on Ge and on Si

HfO2 films were deposited by the reactive sputtering on Ge and Si substrates simultaneously, and we found both the interface layer and the HfO2 film were thinner on Ge substrate than those on Si substrate. A metallic Hf layer has a crucial role for the thickness differences of both interface layer and HfO2 film, since those thickness differences were observed only when an ultrathin metallic Hf layer was predeposited before the reactive sputtering process. The role of metallic Hf in these phenomena is understandable by assuming the formation of a volatile Hf-Ge-O ternary compound at the early stage of the film growth. This result shows that the HfO2/Ge system has an advantage over the HfO2/Si system from the viewpoint of further reduction of the gate oxide film thickness. (C) 2004 American Institute of Physics.