The voltage- and time-dependence of the tunneling currents in polysilicon–oxide–nitride–oxide semiconductor structures have been investigated. Electron and hole contributions were separated using a shallow junction technique. The standard tunneling model for charge injection was successfully applied to describe the observed threshold voltage shifts. For both positive and negative gate voltages, the time-dependence of the current density through the tunneling oxide is given by a simple analytical equation. This equation is characterized by an initial time constant and an asymptotic t−1-dependence. At large programming times the current density follows the t−1-dependence, independent of the tunneling oxide thickness and applied voltage. Under positive polarity (write) electrons are injected from the substrate. Under negative polarity (erase) and previous injection electron back-tunneling rather than hole injection is dominant at the beginning of erasing. At the end of erasing, steady-state conduction can be dominated either by electrons or holes, depending on the applied voltage.

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The structural interface properties of layered Pt/Ti/SiO 2 /Si electrodes have been investigated using high-resolution specular and diffuse x-ray reflectivity under grazing angles. Currently this multilayer system represents a technological standard as bottom electrodes for ferroelectric thin film applications. For the electronic and ferroelectric properties of integrated devices, the film-electrode interface is of crucial importance.We focused on Pt-100nm/Ti-10nm/SiO 2 /Si electrodes prepared under annealing conditions as employed in industrial processing, prior to the deposition of ferroelectric films. The comparison between annealed and non-annealed electrodes clearly revealed strong interfacial effects due to interdiffusion and oxidation of Ti, especially at the Pt-Ti interface. Migration of Ti into the Pt-layer results in a clear shift of the critical angle due to enclosure of TiO 2-x within the Pt-layer. The heterogeneous distribution of TiO 2-x suggests a diffusion mechanism mainly along the Pt-grain boundaries. At the SiO 2 interface a relatively weakly oxidized, remaining Ti-layer of 20 Å could be found, which is most probably correlated with the remaining adhesion to the substrate.