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

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 E_d 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 E_di decreases linearly with the electric field E_ox across the SiO₂ layer. This behavior is attributed to the alignment of the Si–H dipole moment with respect to E_ox, 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. © 2002 American Institute of Physics.