First-principles modelling results, including the formation, migration and activation energies for B and O diffusion through bulk and grain boundaries in polycrystalline HfO2 films, were presented. The modelling results clearly indicated that B and O could penetrate through a 4nm HfO2 film via grain boundary diffusion, but not via bulk diffusion. Secondary ion mass spectrometric analysis of B concentration profiles for polysilicon/HfO2/Si gate stacks after different anneals showed double B peaks at the interfaces and thus confirmed the modeling prediction.

Ab Initio Modelling of Boron and Oxygen Diffusion in Polycrystalline HfO2 Films. C.L.Liu: Physica Status Solidi B, 2002, 233[1], 18-23