Interface reactions of high-kappa Y2O3 gate oxides with Si

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