Jahn–Teller d-state term splittings in Ti, Zr, and Hf elemental oxides: Intrinsic bonding/anti-bonding states and conduction/valence band edge intrinsic defects

Densities of interfacial and bulk defects in high-κ dielectrics are typically at least two orders of magnitude higher than in Si–SiO2 devices. An asymmetry in hole and electron trapping is a significant limitation for Si device operation and reliability. There are two critical issues: (i) are these defects intrinsic, or are they associated with processed introduced impurities? and (ii) what are local atomic arrangements and electronic structure at these defect sites, and can these defects be reduced? This paper presents spectroscopic studies of thin film nanocrystalline high-κ gate dielectrics: TiO2, ZrO2, and HfO2 (the IVB TM oxides) that have identified the electronic structure of intrinsic bonding states and, the intrinsic bonding defects as well. The multiplicity of d-state spectral features are interpreted in terms of Jahn–Teller (J–T) term splittings. Conduction band d-states and defects in films >3 nm display Jahn–Teller d-state splittings, and these have been eliminated in three ways; (i) by reducing film thickness to less than about 2.5 nm, (ii) by SiO2 inclusions in phase separated Hf and Zr silicates with >50–60% TM oxide content, and (iii) by incorporation N-atoms into HfO2 by 700 °C annealing in NH3.