Reaction of barium oxide threshold voltage tuning layers with Si O2 and Hf O2 Si O2 gate dielectrics

We have investigated the reactions of ultrathin BaO capping layers with Si O2 and Hf O2 Si O2 dielectrics using medium energy ion scattering. BaO readily forms a silicate at high temperatures, intermixing with Si O2. Unlike other silicate-forming systems, Ba diffuses throughout the volume of available Si O2, creating a dilute metal oxide. However, when deposited on a Hf O2 Si O2 layer, a Ba silicate layer nucleates at the Hf O2 Si O2 interface, leaving an Si O2 -like buffer layer. The reaction with Si O2 is markedly different from other silicate-forming metal oxides, where nucleation of distinct phases is observed. © 2008 American Institute of Physics.