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

Utilizing remote NH3/H2 plasma on GeO2/Ge can achieve the nearly-free interfacial layer and low equivalent oxide thickness of ∼0.4 nm by the formation of tetragonal ZrO2 phase. However, the electrical defects in ZrO2 result in a large C-V hysteresis (∼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 ∼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.