Spectroscopic studies of O-vacancy defects in transition metal oxides

Abstract

Dielectrics comprised of nano-crystalline HfO2 in gate stacks with thin SiO2/SiON interfacial transition regions display significant asymmetries with respect to trapping of Si substrate injected holes and electrons. Based on spectroscopic studies, and guided by ab initio theory, electron and hole traps in HfO2 and other transition metal elemental oxides are assigned to O-atom divacancies clustered at internal grain boundaries of nano-crystalline films. Engineering solutions in which grain boundary defects are suppressed include: (i) ultra-thin, <2 nm, HfO2 fims, (ii) chemically phase separated high HfO2 content silicate films, and (iii) non-crystalline Zr/Hf Si oxynitride films.