Layer structure variation of thermal-processed thin HfO2 films using X-ray Reflectivity and X-ray Photoelectron Spectroscopy

As transistor feature sizes scaling down, the ultra-thin HfO₂ high-k dielectric has been used to replace SiO₂ for the gate dielectric for a better EOT. Grazing Incidence X-ray Reflectivity (GIXRR) is an accurate instrument to analyze the ultra-thin HfO₂ films non-destructively based on an appropriate material model. However, the interfaces between layers of the ultra-thin HfO₂ and other oxide films are not easily identified, especially when post-deposition annealing (PDA) process is applied. In this work, X-ray Photoelectron Spectroscopy (XPS) was used to evaluate the layer structures which were post-annealed up to 1000°C using furnaces in the Ar ambiances. The experimental results and analysis showed that layer thicknesses, crystal phases and chemical structures of the ultra-thin HfO₂ films were significantly dependent on annealing temperatures. The structure analysis of the GIXRR spectra using the modified material structure model from the XPS analysis confirmed the interfacial broadening induced by the post-deposition annealing.