Characteristics of atomic-layer-deposited HfO2 films by using a remote plasma on pre-deposited Hf metal layer

Abstract

We investigated the physical and the electrical properties of HfO2 films grown by using a remote-plasma atomic layer deposition technique on a pre-deposited Hf metal layer. The Hf metal pre-deposited film retarded effectively the growth of an interfacial layer while the HfO2 film without a Hf metal layer showed a growth of an interfacial layer. The as-deposited HfO2 layers on thick Hf metal layers are crystallized while those on thin Hf metal layers remain amorphous. The pre-deposited Hf metal layer decreased the equivalent oxide thickness while it increased the crystallization temperature. The flat-band voltage (V-FB) shifted in the negative direction with increasing pre-deposited Hf metal thickness and the effective fixed oxide charge density corresponding to the Delta V-FB of the HfO2 films increased with increasing pre-deposited Hf metal thickness. After annealing at 800 degrees C, the V-FB for the HfO2 films shifted toward the ideal V-FB and the effective fixed oxide charge decreased. The Hf pre-deposition technique was found to be effective in reducing the EOT by suppressing interfacial layer growth while the electrical properties, such as the leakage current density and the effective fixed oxide charge density, were degraded.