Intrinsic bonding defects in transition metal elemental oxides

摘要

Gate dielectrics comprised of nanocrystalline HfO_2 in gate stacks with thin SiO_2/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 HfO_2 and other transition metal elemental oxides are assigned to O-atom divacancies, clustered at internal grain boundaries. Three engineering solutions for defect reduction are identified: ⅰ) deposition of ultra-thin, < 2 nm, HfO_2 dielectric layers, in which grain boundary formation is suppressed by effectively eliminating inter-primitive unit cell π-bonding interactions, ⅱ) chemically phase separated high HfO_2 silicates in which inter-primitive unit cell p-bonding interactions are suppressed by the two nanocrystalline grain size limitations resulting from SiO_2 inclusions, and ⅲ) non-crystalline Zr/Hf Si oxynitrides without grain boundary defects.