Hard X‐ray photoemission experiments on novel Ge‐based metal gate/high‐k stacks

The scaling of CMOS devices makes mandatory the study of new materials to overcome the physical limitations of the Si technology. Germanium is a good candidate to replace silicon for the channel to improve the carrier mobility. High‐K dielectrics such as HfO2 are investigated to replace the gate oxide (SiO2) to decrease both leakage currents and EOT. For the gate electrode, it is also crucial to move from poly‐silicon to a metal gate like TiN to adjust work function and to suppress poly‐depletion in order to decrease EOT. However, to reach optimal device performances, both the Ge/high‐K and high‐K/TiN interfaces need to be optimized. In order to passive and prevent Ge oxidation we have deposited a very thin Si interlayer prior to the high‐k growth. A thin Si layer (Si capping) is epitaxially grown on Ge and then partially oxidized before high‐k deposition. The exact control of the Si capping layer is of major importance. It must be enough thick to prevent germanium oxidation when the partial oxidation of ...