First-Principles-Calculation Method for Optimizing Strain to Reduce Gate Leakage Current in MOS Transistors with Silicon Oxynitride Gate Dielectrics

Abstract

We developed a method for optimizing strain to reduce gate leakage current in metal-oxide-semiconductor (MOS) transistors by using first-principles calculations. This method was used to investigate the possibility of decreasing gate leakage current by controlling the strain on gate dielectric materials. We found that tensile strain increases the leakage current through both silicon oxide (SiO2) and silicon oxynitride (SiON) gate dielectrics, whereas compressive strain hardly changes the leakage current through SiO2 gate dielectrics and decreases the leakage current through SiON gate dielectrics. These changes reflect strain-induced changes in the band gaps of these materials. Using finite element analysis to estimate the strain in MOS transistors, we showed the usability of SiON in terms of gate leakage currents and the importance of controlling the strain on the gate dielectric materials.