Interface reactions of high-κ Y2O3 gate oxides with Si

Ultrathin Y2O3 films were electron beam evaporated in an ultrahigh vacuum onto Si(100) and investigated by high-resolution medium energy ion scattering. Selected films were capped in situ with amorphous Si. Uncapped films that were exposed to air prior to analysis contained excess oxygen compared to a stoichiometric Y2O3 film, and showed a 6-8 Angstrom interfacial layer. Si uptake from the substrate occurred in these films after a 700 degreesC vacuum anneal, presumably by reacting with the excess oxygen. Si-capped Y2O3 films on the other hand were stoichiometric, and the substrate interface was sharp (less than or equal to2 Angstrom), even after 900 degreesC vacuum anneals. No change was seen at the Y2O3 capping layer interface until greater than or equal to 800 degreesC for vacuum anneals. These measurements indicate that control of the interface composition is not possible after exposure of ultrathin Y2O3 films to air. (C) 2001 American Institute of Physics.