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 (Si-3=SiH-->Si-3=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. (C) 2002 American Institute of Physics.