Electrical characteristics of SiOxFy gate oxides formed by a plasma fluorination technique

The electrical characteristics of metal-oxide-semiconductor capacitors with ultrathin fluorinated SiO2 formed by a plasma fluorination technique have been studied and correlated with the chemical properties. Our study showed that the fluorination of conventional SiO2 results in a reduction of leakage current and a small amount of fluorine doping can increase the oxide capacitance. From the analysis of electrical properties and x-ray photoelectron spectroscopy, the increase and decrease of capacitance for small and large amounts of F doping were attributed to filling up the dangling bonds with fluorine at the surface and the formation of fluorine-rich oxyfluoride in the bulk, respectively. The reduction of leakage current can be explained by the removal of hopping states or trap states originating from the Si dangling bonds and Si–H bonds and the resulting higher-energy barrier for the tunneling process.