Roughness at ZrO2/Si interfaces induced by accelerated oxidation due to the metal oxide overlayer

We investigated reactions at ZrO2/Si interfaces by means of interface oxidation and atomic-scale roughness caused by postoxidation annealing. When fabricating ZrO2 by in situ reoxidation of a thin Zr metal layer, the interface oxidation that results in Zr-silicate formation accelerates, when the initial Zr layer becomes thicker. This implies that interface oxidation is not dominated by oxidant diffusion through the high-k film, but is accelerated by catalytic effects that occurs within the metal oxide. We also found that, in contrast with a SiO2/Si interface, roughness at the high-k/Si interface monotonously increases with the growth of the interface silicate layers. These results demonstrate the importance of postannealing conditions on high-k gate dielectrics. (C) 2003 American Institute of Physics.