Modeling the effects of lanthanum, nitrogen, and fluorine treatments of Si-SiON-HfO2-TiN gate stacks in 28 nm high-k-metal gate technology

We have carried out a combined experimental and theoretical study on the influence of lanthanum, nitrogen, and fluorine treatments on the electric properties of high-k metal gate (HKMG) devices. In particular, we have developed a theoretical gate stack model which is able to predict qualitatively and quantitatively the influence of nitrogen, fluorine, and lanthanum treatments on the characteristic electric properties of Si-SiON-HfO2 gate stacks. The combination of this theoretical model with experimental investigations of several differently treated HKMG devices allows the estimation of the amount of incorporated impurity atoms in different material layers. Furthermore, we propose an atomistic mechanism for the incorporation of lanthanum and fluorine impurity atoms and we can explain the results of recent leakage current measurements by a passivation of oxygen vacancies within the HfO2 layer.