Evidence of GeO volatilization and its effect on the characteristics of HfO2 grown on Ge substrate

HfO₂ films are deposited by atomic layer deposition (ALD) using tetrakis ethylmethylamino hafnium (TEMAH) as the hafnium precursor, while O₃ or H₂O is used as the oxygen precursor. After annealing at 500℃ in nitrogen, the thickness of Ge oxide's interfacial layer decreases, and the presence of GeO is observed at the H₂O-based HfO₂ interface due to GeO volatilization, while it is not observed for the O₃-based HfO₂. The difference is attributed to the residue hydroxyl groups or H₂O molecules in H₂O-based HfO₂ hydrolyzing GeO₂ and forming GeO, whereas GeO is only formed by the typical reaction mechanism between GeO₂ and the Ge substrate for O₃-based HfO₂ after annealing. The volatilization of GeO deteriorates the characteristics of the high-κ films after annealing, which has effects on the variation of valence band offset and the C–V characteristics of HfO₂/Ge after annealing. The results are confirmed by X-ray photoelectron spectroscopy (XPS) and electrical measurements.