Effect of thermal annealing on charge exchange between oxygen interstitial defects within HfO2 and oxygen-deficient silicon centers within the SiO2/Si interface

We compare the charging response of rapid thermally annealed (800 and 1000 °C) 4 nm thick HfO2 to as-deposited HfO2 on Si by measuring the surface potential of the HfO2 layers after vacuum ultraviolet (VUV) irradiation with 11.6 eV photons. From VUV spectroscopy, we determined all HfO2 layers show the presence of oxygen-interstitial defects (OIDs). The electronic states of OID in HfO2 line up in energy with oxygen-deficient Si centers within the SiO2 interfacial layer. This implies charge exchange between OIDs within HfO2 and the O-deficient silicon centers within the SiO2 interfacial layer are very important for controlling the radiation-induced trapped charge in HfO2 dielectric stacks.