Tungsten nanocrystals embedded in high- k materials for memory application

Abstract

The formation of tungsten nanocrystals (W-NCs) on atomic-layer-deposited HfAlO Al2 O3 tunnel oxide was demonstrated for application in a memory device. It was found that the density and size distribution of W-NCs are not only controlled by the initial film thickness, annealing temperature, and time, but also by the metaltunnel oxide interface structure. Well-isolated W-NCs with an average diameter of 5 nm and a surface density of 5× 1011 cm-2 were obtained by applying a thin Al2 O3 wetting layer onto HfAlO tunneling oxide. A large flatband voltage shift of 5.7 V was observed from capacitance-voltage measurement when a bias voltage up to ±4 V was applied. © 2005 American Institute of Physics.