Electrical characterization of HfO2 films obtained by UV assisted injection MOCVD

HfO2 films were deposited at low temperature (∼400 °C) by UV assisted injection metal-organic chemical vapor deposition (UVI-MOCVD). A three-step process was used for this study, consisting of (A) Pre-deposition anneal for nitridation; (B) Deposition step; (C) Post-deposition annealing in oxygen. Special attention was paid to the effect of UV exposure during these steps. Films were characterized by physical, optical and electrical techniques. Thickness was determined by different methods (X-ray Reflectrometry (XRR), spectroscopic ellipsometry and transmission electron microscopy) and a good agreement was found for all samples. The HfO2 permittivity, equivalent oxide thickness (EOT), flat-band voltage (Vfb) and total charge (Qt) were extracted from the CV response at high frequency taking into account the HfO2 and SiO2 thicknesses obtained by XRR. The calculated permittivity values were in the range 7-13, i.e. lower than theoretical values for the monoclinic phase. Explanations are suggested in the context of the other characterizations. JEeff characteristics were constructed taking into account the EOT values (Eeff = V/EOT). Effective breakdown fields range between 8.7 and 16.9 MV/cm. No dependence of Eeff with UV exposure was found.