Characterization of the interface between the Hf-based high-k thin film and the Si using spatially resolved electron...

The interfacial structures of HfO(2) and HfAlO thin films on Si have been investigated using spatially resolved electron energy-loss spectroscopy. We have found that interfaces are not atomically sharp, and variation in the symmetry of the local atomic coordination lasts for a couple of monolayers for both the as-deposited HfO(2) and the HfAlO samples. Annealing of the HfO(2) film in the oxygen environment leads to the formation of a thick SiO(2)/SiO(x) stack layer in-between the original HfO(2) and the Si substrate. As a comparison, the interfacial stability is significantly improved by Al incorporation into the HfO(2) film (forming HfAlO), which effectively reduced/eliminated the interfacial silicon oxide formation during the oxygen annealing process. The mechanism of the high-k film/substrate stabilization by Al incorporation is discussed based on the experimental results.