Probing Point Defects in Stacks of Ultrathin High-k Metal Oxides on Semiconductors by Electron Spin Resonance: The Si/HfO2 vs the Ge/HfO2 System

Abstract

Combined electron spin resonance and electrical analysis of (100)Si/HfO2 and (100)Ge/HfO2 interfaces reveals dramatic differences in their interface defect properties. No interfacial Ge dangling bond type defects could be revealed. The observed paramagnetic defects do not correlate with the slow acceptor states dominating the Ge/insulator trap spectrum, and are resistant to passivation. The dangling bond type defects observed, upon hydrogen detachment, at the (100)Si/HfO2 interfaces are the trivalent Si defects common for Si/SiO2 interfaces, Pb0 and Pb1 centers. The density of the Pb0 is higher than in the (100)Si/SiO2 structures and is sensitive to the deposition process. However, the density can be significantly reduced by annealing of the Si/HfO2 structures in O-containing ambient, likely through re-establishing the Si/SiO2 interface. The density of fast interface states closely follows the variations in the Pb0 center density, suggesting it as the dominant contribution to the fast interface states.