Atomistic Modeling of Oxide Defects

Abstract

In this chapter we focus on the atomistic modeling of oxide defects in order to shed some light on the microscopic nature of random telegraph noise (RTN) and bias temperature instability (BTI). Density functional theory (DFT), arguably the most popular method in computational chemistry, allows the study of defects at an atomistic level from first principles. Here we will give a short introduction into the theoretical foundation of DFT and the methodology of modeling amorphous oxide materials. Furthermore we will briefly recap the mechanism of charge trapping at defects within the successful nonradiative multiphonon (NMP) model and explain the connection of its parameters to DFT simulations. At the end we will discuss the most promising defect candidates for RTN and BTI, and compare their theoretical characteristics obtained with DFT to parameters extracted from recent experimental data using the NMP model. Here our focus lies on defects in amorphous silica (a-SiO2) and hafnia (a-HfO2), which are the most relevant gate dielectrics for modern MOSFET devices. It will be demonstrated that the results from DFT generally are in good agreement with experimentally observed defect behavior, consolidating the physical validity of the NMP model.