Enhancement in thermal stability of atomic layer deposited HfO 2 films by using top Hf metal layer

Abstract

A thin (∼ 0.5 nm) layer of Hf metal was deposited on an atomic layer deposited (ALD) HfO 2 film by the DC sputtering method. X-ray photoelectron spectroscopy and high-resolution transmission electron microscopy analyses showed that the Hf metal layer transformed into HfO 2 during the post-deposition annealing process. It appears that the HfO 2 layer formed by the oxidation of Hf metal provided the underlying ALD HfO 2 layer with the nucleation sites necessary to decrease the grain-boundary density of the crystallized HfO 2 film. The decrease in the grain-boundary density resulted in a reduction in the Hf-silicate formation and interfacial layer growth during post deposition annealing. This eventually resulted in a smaller increase in the capacitance equivalent thickness (CET) and high-k characteristics in the CET vs. leakage current density curve even after post deposition annealing at 1000 °C.