Hysteresis reduction by fluorine incorporation into high permittivity tetragonal ZrO2 on Ge

Utilizing remote NH3/H-2 plasma on GeO2/Ge can achieve the nearly-free interfacial layer and low equivalent oxide thickness of similar to 0.4 nm by the formation of tetragonal ZrO2 phase. However, the electrical defects in ZrO2 result in a large C-V hysteresis (similar to 580 mV). The fluorine incorporation by CF4 plasma is demonstrated to effectively passivate these defects both experimentally and theoretically. The hysteresis is reduced to be similar to 200 mV, and the interface defect density, permittivity, and gate leakage current remain intact. The Zr-F bond formation to remove the midgap states calculated by the density-function-theory may be the origin of passivation. (C) 2014 AIP Publishing LLC.