Effects of annealing on the valence band offsets between hafnium aluminate and silicon

Abstract

In this work, we examine the valence band offset of hafnium aluminate (HfAlO), a material of interest for use as a high dielectric constant (high- k) gate oxide, following postdeposition annealing. It is observed that annealing leads to a change in the band offset between the high- k oxide and the semiconductor. Our results conclusively show that the change is due to the existence of an electrostatic dipole field at the interface between HfAlO and the silicon substrate. This provides evidence to partly account for the observed flatband voltage shifts in high- k dielectric stack structures in the literature. The origin of the dipole field is also discussed in terms of the interfacial permittivity. © 2008 American Institute of Physics.