Theory of Metal/Dielectric Interfaces -Breakdown of Schottky Barrier Limits-

Recent development of VLSI technique requires wide variety of controlled interfaces especially in high-k metal gate technologies. As for metal/dielectric interfaces, they have been intensively studied, and a lot of knowledge and concepts have been proposed so far. In this paper, we point out the breakdown of the two Schottky barrier limits of Bardeen and Schottky limits which has been believed for a long time as the intrinsic limit of Schottky barrier heights, by considering the characteristics of metal density of states and the atomistic structures of metal/insulator interfaces. Moreover, we have experimentally confirmed that Fermi level of Au (typical high work function metal) further lowers, when Au is in contact with HfO2, by photoemission measurements, indicating the breakdown of the Schottky limit.