Interfacial defect states in HfO2 and ZrO2 nMOS capacitors

A comprehensive analysis of the bump/kink observed in the experimental capacitance-voltage (C-V) curves of HfO2 and ZrO2 capacitors was performed using self-consistent numerical simulations. Both HfO2 samples grown by sputter deposition and grown by metal-organic chemical vapor deposition (MOCVD) were examined. The bumps in the C-V curves were found to be consistent with an interface state centered 0.25 eV above the valence bandedge for the sputter deposited devices, and 0.30 eV above the bandedge for the MOCVD devices. Annealing of the HfO2 devices reduced the densities of these traps, but also increased the effective oxide thickness. Similar defect states were detected for the ZrO2 devices centered 0.25 eV above the valence bandedge.