Investigation of oxidation process on plasma treated thin Al-films by GIXR and GIXRD

Abstract

The sensitivity of grazing incidence X-ray reflectometry (GIXR) for amorphous as well as crystalline layers and for layer formations in the nm-range combined with information about structural states by grazing incidence X-ray diffractometry (GIXRD) enable these methods to study interfaces and surface layers. Thin aluminium layers (30–60 nm) were deposited on Si by thermal evaporation. These Al-layers were plasma oxidized for 5 h with interruptions every hour. The plasma treatments were carried out in a 2.45 GHz microwave discharge (SLAN-slot antenna) with different plasma types (Ar, O2) at low temperatures. In this way a thin oxide layer additional to the native alumina on the top was formed. The properties of the oxide layers such as thickness, roughness and density were studied by GIXR. The chemical composition was investigated by GIXRD and XPS. In addition AFM was used for surface topography observations. All these methods were applied before and after the plasma treatment. The properties of the thin Al-oxide layers were found to depend on the type of plasma but in all cases plasma leads to a smoothing of the films as well as an increasing of the thickness of the upper alumina layer.