Reaction of barium oxide threshold voltage tuning layers with SiO2 and HfO2/SiO2 gate dielectrics

We have investigated the reactions of ultrathin BaO capping layers with SiO(2) and HfO(2)/SiO(2) dielectrics using medium energy ion scattering. BaO readily forms a silicate at high temperatures, intermixing with SiO(2). Unlike other silicate-forming systems, Ba diffuses throughout the volume of available SiO(2), creating a dilute metal oxide. However, when deposited on a HfO(2)/SiO(2) layer, a Ba silicate layer nucleates at the HfO(2)/SiO(2) interface, leaving an SiO(2)-like buffer layer. The reaction with SiO(2) is markedly different from other silicate-forming metal oxides, where nucleation of distinct phases is observed. (c) 2008 American Institute of Physics.