Bond Order Potential for Accurate Growth Process Simulation of Indium Gallium Zinc Oxide

Abstract

In this work, we parameterized Analytic Bond Order Potential (ABOP) for Molecular Dynamics (MD) studies of growth simulation and structure prediction of Indium-Gallium-Zinc-Oxide (IGZO). The potential parameterization was based on Density Functional Theory (DFT) calculated results and the experimental values to capture the realistic bonds of the IGZO compounds [1]. The ABOP demonstrated stability under room temperature simulation conditions, maintaining crystallinity and showing excellent agreements in the x-ray diffraction (XRD) data with the experimental results [2]. Moreover, the ABOP proved to be versatile across a wide range of temperatures, as demonstrated by its ability to reconstruct an amorphous phase (a-IGZO) using the melt-quenching method. The simulation-generated a-IGZO exhibited an increase in bond lengths between metal components, resulting in a decrease in density from 5.9 g/cm3 to 5.69 g/cm3, consistent with the experimental results [1]. The wide transferability of the ABOP was demonstrated by the simulation of a film fabrication through sputtering simulation, using an InGaZnO4 target at room temperature conditions. The simulated sputter-grown film exhibited an atomic ratio of In : Ga : Zn = 1 : 0.93 : 0.58, similar to the real sputter-grown a-IGZO films [3]. However, the film showed low oxygen content, with a ratio just about 2.5 times higher than that of the indium. This is not ideal, as a lack of oxygen indicates oxygen vacancies in the sputter-grown films which could lead to negative bias stress (NBS) which causes device degradations [4]. To address this issue, the simulation result recommends the use of the high oxygen ratio target (InGaZnO6) to achieve a film growth of an atomic ratio of In : Ga : Zn : O = 1 : 0.93 : 0.65 : 3.5, which is similar to the ratio of InGaZnO4. Overall, this study demonstrates that the developed ABOP is suitable for simulating the dynamics of the mesoscale IGZO systems, and is accurate in the prediction of the diverse structures and growth simulations. This work will open many research avenues for further investigations of IGZO-based device development.