Effect of hafnium germanate formation on the interface of HfO_2/germanium metal oxide semiconductor devices

摘要

We have studied the thermal stability of HfO_2 thin layers on germanium and the substrate interface development. HfO_2 was deposited on Ge substrates and annealed in O_2 or N_2 at 500℃ (substrate temperature). After O_2 anneal, we observed the formation of hafnium germanate, which is stable at 500℃ in N_2 as opposed to GeO_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 HfO_2 and germanium as compared to silicon. In addition, results suggest that the HfGeO_x is related to the high interface state density frequently reported for germanium metal oxide semiconductor devices.