Effect of Gate Metal Electrode on Chemical Bonding State in Metal/Pr-Oxide/Ge Gate Stack Structure

We investigated the effect of the oxidation-reduction character of metal electrode on the chemical bonding state in metal/Pr-oxide/Ge gate stack structure. The binding energy of the Pr-oxide peak increases with the formation of a metal electrode with the strong reduction character, indicating the change in the valence state of Pr from tetravalent to trivalent. The intensity of the Ge oxide peak changes depending on metal species. It is suggested that some amount of Ge oxide is reduced in the sample with the metal film with the strong reduction character. Therefore, the oxidation-reduction character of metal electrode affects on not only the change in the Pr valence state in oxide film but also the interfacial reaction at the Pr-oxide/Ge interface for metal/Pr-oxide/Ge gate stack structures. These results suggest that a selection of gate metal species with basing on an oxidation-reduction character is quite important since it affects not only the dielectric constant of high-k films but also the interfacial chemical bonding structures in metal/high-k/Ge gate stack structures.