XPS and AFM investigation of hafnium dioxide thin films prepared by atomic layer deposition on silicon

The nucleation and growth of technologically important hafnia (HfO2) ultrathin films on Si-substrates and formation of interface layers were investigated using ex situ synchrotron radiation excited photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) techniques. Atomic layer deposition based on HfCl4-H2O and HfI4-O2 precursor systems was applied to prepare the films. XPS studies showed that the deposition temperature had substantial effect on the first stages of the film growth as well as formation of the interface layers. Considerable delay of hafnia film growth and Hf-silicate (HfSixOy) interface layer formation were observed at high temperature (600 °C) whereas at lower temperature (300 °C), the film started to grow during the first growth cycles and the silicate interface layer was absent. AFM investigations affirmed the XPS results, and showed also that the surface topography had to be known for proper interpretation of XPS data.