Physical charge transport models for anomalous leakage current in floating gate-based nonvolatile memory cells

A model for anomalous charge loss in nonvolatile memories is presented based on the physical description of charge transport through the tunnel oxide. This model considers multiphonon-assistance as well as arbitrary three-dimensional (3-D) distributions of oxide defects (electron traps). After identifying the trap-trap distance as the most important parameter, the 3-D model can be simplified to a tunneling model, which describes one tunneling step only. The consistency of this simplified one-step tunneling model with the percolation model for anomalous charge loss description is shown. A further simplification is achieved by deducing an analytical description of the transient behavior based on the one-step tunneling model.