Post metallization annealing study in La2O3/Ge MOS structure

The study on post metallization annealing (PMA) in electrical characteristics and interfacial properties of La2O3/Ge structures has been conducted. The PMA treatment in N2 ambient induces the growth of interfacial Ge oxide layer accompanied with decrease of capacitance value and interface trap density. The interface-layer growth is caused by the oxidation of Ge substrate due to the hydroxyl group absorbed in La2O3 from the ambient. The metal electrode capping might prevent the hydroxyl from evaporating during annealing, which enhances the interface reaction. On the other hand, leakage current increment has been observed for the sample with PMA in case of using Pt gate electrode. It is due to the diffusion of Pt and/or Ge and a Pt-germanide formation in La2O3 film during PMA. This leakage current increment can be suppressed by using Ta or W electrode which has less reactivity with Ge than Pt at high temperature.