Magnesium metallic interlayer as an oxygen-diffusion-barrier between high-κ dielectric thin films and silicon substrate

The deposition of a thin magnesium metallic interlayer on an Si substrate prior to the deposition of an oxide thin film using rf-sputtering was investigated. The deposition of high-κ HfO2 thin film was more particularly studied and it was demonstrated that the metallic interlayer acts as an oxygen barrier, preventing the formation of a low-κ layer at the high-κ/Si interface during the deposition. A post-deposition annealing treatment performed on the films induced the diffusion of the metal barrier into the HfO2 film and allowed obtaining a sharp interface. However, the degree of diffusion depends not only on the interlayer thickness, but also on the thickness of the high-κ film. X-ray photoelectron spectroscopy was used to study the degree of oxidation of the Mg interlayer. High resolution transmission electron microscopy and energy filtered transmission electron microscopy were used to characterize the films and the diffusion of the Mg interlayer into the high-κ film after annealing. In this work we will stress on the engineering of the interface via the diffusion of the Mg interlayer during the growth process and on annealing. ► HfO2 is prepared by sputtering as a high-κ material. ► We present a method of preventing low-κ interfacial growth. ► The method is based on the pre-deposition of a magnesium metallic interlayer. ► The effect of the post-deposition annealing under nitrogen is also studied.