Model for interface defect and positive charge generation in ultrathin SiO2/ZrO2 gate dielectric stacks

Abstract

The generation of interface defects and positive charge during the injection of electrons in p-Si/SiO2/ZrO2/TiN structures is investigated. The kinetics of generation of both type of defects are found to be very similar. A model is proposed to explain the interface defect generation, based on the depassivation of trivalent silicon dangling bonds (Si3≡SiH→Si3≡Si⋅) at the (100)Si/SiO2 interface by the injected electrons. A Gaussian spread for the activation energy Ed related to the dissociation of the Si–H bond is included in this model. Comparison with experimental results reveals that the mean value of the activation energy Edi decreases linearly with the electric field Eox across the SiO2 layer. This behavior is attributed to the alignment of the Si–H dipole moment with respect to Eox, which favors dissociation of the Si–H bond. The hint of a correlation between the interface defect and positive charge generation suggests that the positively charged centers might be hydrogen-induced overcoordinated oxygen centers.