O-vacancies in (i) nanocrystalline HfO2 and (i) noncrystalline SiO2 and Si3N4 studied by x-ray absorption spectroscopy

Abstract

Performance and reliability of semiconductor-oxide-metal devices with high-κ gate dielectrics are limited by electronically active O-atom vacancy defects. Synchrotron x-ray spectroscopy defect features have been interpreted using two-electron multiplet theory. This approach quantifies conduction band edge and pre-edge features assigned to intrinsic bonding effects. Theoretical studies based on density functional theory have identified these defects as neutral and negatively-charged O-atom vacancies in transition metal (TM) oxides including HfO2 and ZrO2. However, agreement between calculated electronic states and experiment has been less than satisfactory. In this paper the O-vacancy electronic structure is addressed using a theoretical approach extended from multiplet theory traditionally applied to occupied intrinsic, and alloy and impurity atom d states in TM oxides. An equivalent d2 model based occupation of two d orbitals of the TM atoms that border the neutral vacancy site has been used to determine...