Fluorine incorporation at HfO2∕SiO2 interfaces in high-k metal-oxide-semiconductor gate stacks: Local electronic structure

Effects of fluorine incorporation on the electrical properties of HfO2∕SiO2 dielectric stacks are investigated through both ab initio simulations and electrical measurements. The results show that F ions are able to remove midgap states resulting from undercoordinated Hf ions at the HfO2∕SiO2 interface. They also indicate that F incorporation increases the leakage current if an excessive amount of F ions are present in the dielectric, beyond that required to passivate the undercoordinated interfacial Hf ions. A possible way to maximize the benefits of F incorporation for high-k gate stack electrical characteristics is discussed.