Electrical Characterization of ALD Al2O3and HfO2Films on Germanium

Al2O3and HfO2films were deposited on germanium substrates by atomic layer deposition (ALD) and analyzed by MOS capacitor electrical characterization. In-situ plasma nitridation performed prior to ALD was found to improve the stability of the interface. For Al2O3/GeON/Ge capacitors, a 450°C anneal in nitrogen ambient reduced hysteresis and oxide fixed charge to 90 mV and 1012cm-2respectively, with low leakage current density. On the contrary, degradation was observed for un-nitrided Al2O3/Ge capacitors after 300 and 400°C post-metal anneals. HfO2/GeON/Ge capacitors benefitted from a 400°C densification anneal but exhibited degradation after post-metal anneals at temperatures greater than 300°C. This degradation is attributed to the influence of Al electrodes on the HfO2gate stack. HfO2is considered to be a suitable material for the gate stack and Al2O3for the buried dielectric in a GeOI structure.