Experimental Characterization of Statistically Independent Defects in Gate Dielectrics—Part II: Experimental Results on Flash Memory Arrays

Abstract

In this paper we applied the statistical model for independent defects described in Part I, to experimental data measured on Flash memory arrays. The model, developed to describe the stress-induced leakage current (SILC) statistics, allowed us to study the oxide trap generation during program/erase (P/E) stress and to extract the discrete probability distribution (DPD) of the gate current increase due to the single oxide defect. For all the analyzed nonvolatile memory arrays and for all the P/E stresses, the experimental results are consistent with the simulations carried out in Part I, thus confirming the reliability of the statistical model and of its validation procedure. Measurements on Flash cell arrays with different oxide thickness show that the number of generated oxide traps increases linearly with the number of P/E cycles in the early stage of the stress. It is shown, for the first time, that the extracted DPD of the single-trap exhibits long tails with power law dependence on the trap current and with a slope of the tail that decreases with decreasing oxide thickness. These tails are responsible for the cells with the largest SILC values in the Flash memory arrays.