Roughness evolution during the atomic layer deposition of metal oxides

Abstract

The evolution of the surface roughness during the atomic-layer deposition (ALD) of Al2O3, NiO, and HfO2 was studied by atomic-force microscopy and nonspecular x-ray reflectance. The results indicate that the crystallinity of the films played a crucial role in the roughness evolution during ALD. While the ALD of amorphous oxide films showed replication of the initial starting surface with no roughness build-up, the ALD of polycrystalline oxide films led to a strong anomalous dependence of the roughness on the film thickness. This behavior is explained within a model taking into account spatial variations of the adsorption site density.