Evidence of GeO volatilization and its effect on the characteristics of HfO2 grown on a 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 °C 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