Effect of hafnium germanate formation on the interface of HfO2/germanium metal oxide semiconductor devices

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Abstract
We have studied the thermal stability of Hf O 2 thin layers on germanium and the substrate interface development. Hf O 2 was deposited on Ge substrates and annealed in O 2 or N 2 at 500 ° C (substrate temperature). After O 2 anneal, we observed the formation of hafnium germanate, which is stable at 500 ° C in N 2 as opposed to Ge O 2 that desorbs as GeO. We believe that this hafnium germanate is an oxygen barrier and as such is at the origin of the much thinner interface between Hf O 2 and germanium as compared to silicon. In addition, results suggest that the Hf Ge O x is related to the high interface state density frequently reported for germanium metal oxide semiconductor devices.