It was recalled that Ge was known to diffuse into high-k dielectrics during Ge-based metal oxide semiconductor transistor processing, thus causing degradation of gate dielectrics. In order to explore the origins of the degradation, first-principles calculations were performed, based upon density functional theory, in order to study Ge-related defects in HfO2. According to the calculations, Ge at an O vacancy was responsible for the experimentally observed negative charge, gate leakage, and hysteresis enlargement while interstitial Ge in HfO2 was only responsible for the increased gate leakage. The results indicated that the passivation of O vacancy was extremely important during Ge-based metal oxide semiconductor transistor processing.

Impact of Germanium Related Defects on Electrical Performance of Hafnium Oxide. Q.Q.Sun, Y.Shi, L.Dong, H.Liu, S.J.Ding, D.W.Zhang: Applied Physics Letters, 2008, 92[10], 102908