The thickness measurement of ultrathin films from new high-k material HfO2 by grazing incidence x-ray reflectivity

Abstract

The thickness of HfO2 ultrathin films was determined by grazing incidence x-ray reflectivity (GIXRR) with simulation. Two samples were prepared by atomic layer deposition, and the Si substrate of one sample was treated by HFacid (1:20) to erase the native oxide layer, while the other was not. According to the GIXRR, the films consisted of two contamination layers, an interface layer, a HfO2 layer and a native oxide layer (except for the acid-treated sample) from top to bottom. As a result, the HfO2 thickness of the two samples was 1.23 nmand 1.25 nmrespectively, and the thicknesses of the interface layers between the HfO2 and the Si substrate were 0.1 nmand 0.95 nmrespectively. The chemical states of the film were investigated by ultrasonification and x-ray photoemission spectroscopy (XPS), and the thickness was verified by transmission electron microscopy (TEM). All these phenomena proved that GIXRR is a powerful and effective piece of technology for characterizing HfO2 ultrathin film.