A non-defect precursor gate oxide breakdown model

Abstract

Understanding defect creation is central to efforts to comprehend gate dielectric breakdown in metal-oxide-semiconductor-field-effect-transistors (MOSFETs). While gate dielectrics other than SiO2 are now popular, models developed for SiO2 breakdown are used for these dielectrics too. Considering that the Si–O bond is very strong, modeling efforts have focused in ways to weaken it so that defect creation (bond-breaking) is commensurate with experimental observations. So far, bond-breaking models rely on defect-precursors to make the energetics manageable. Here, it is argued that the success of the percolation model for gate oxide breakdown precludes the role of defect precursors in gate oxide breakdown. It is proposed that defect creation involves “normal” Si–O bonds. This new model relies on the fact that hole transport in SiO2 is in the form of a small polaron—meaning that it creates a transient local distortion as it travels. It is this transient distortion that enables normal Si–O bonds to be weakened (albeit transiently) enough that breaking the bonds at a rate commensurate with measurements becomes possible without the help of the externally applied field.