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℃ in nitrogen,the thickness of Ge oxide's interfacial layer decreases,and the presence of GeO is observed at the H2 O-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 H2 O molecules in H2 O-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.