Temperature activation of the string current and its variability in 3-D NAND flash arrays
Davide Resnati, Aurelio Mannara, Gianluca Nicosia, Giovanni M. Paolucci, Paolo Tessariol, Andrea Leonardo Lacaita, Alessandro Sottocornola Spinelli, Christian Monzio Compagnoni · 2017
In this work, we present the first statistical analysis of the temperature activation of the string current in vertical-channel NAND Flash arrays. To this aim, a 3-Dimensional (3-D) TCAD model for current transport through the thin polysilicon channel of NAND strings is developed and calibrated against experimental data over a wide temperature range. This calibration allows to highlight the main features of current transport through the polysilicon grain boundaries as a function of the string current level and temperature, for different grain sizes. The model is then used to address the statistical dispersion of the temperature activation of the string current during read and of the temperature-induced shift of cell threshold-voltage (Vt) coming from the variability in the configuration of the polysilicon grains. Results reveal that this variability represents a nonnegligible source of statistical broadening for the cell Vt distribution when changing the array temperature.