Impact of incorporated Al on the TiN/HfO2 interface effective work function

First principles calculations of the impact of Al incorporation on the effective work function of a TiN/HfO2 interface are presented. The undoped interface has a midgap effective work function. We find that Al in the metal and Al substituting for O in the dielectric make the effective work function more n-type. More importantly, Al substituting for Hf in the oxide near the interface-the energetically stable position for most growth conditions-increases the effective work function, making it more p-type. Furthermore, the shift of the work function increases with increasing the Al concentration at the interface. The calculated results are consistent with experimental data. (C) 2008 American Institute of Physics. [DOI: 10.1063/1.2986158]