Bias and W/L dependence of capacitive coupling coefficients in floating gate memory cells

In this paper, a complete study of capacitive coupling coefficients depende nce on bias and W/L will be presented, including a review on classic method s to extract their value from electrical characterization. Capacitive coupl ing ratios have been usually adopted to model floating gate (FG) memory cel ls, in particular to deduce the value of FG potential. Now they are determi ned by means of a new model (recently proposed in the literature), starting from a new procedure to evaluate the FG potential. Results obtained with t his new model will be compared to classic values. Particularly, their bias dependence (during write/read/erase of Flash memory cells) will be deeply i nvestigated, thus demonstrating the limits of considering them constants, a s is usually done. By analyzing their W/L dependence, we will deduce useful information on the effects of scaling and the role played by fringing capa citances. The most important methods reported in the literature to estimate the control gate and drain capacitive coupling ratios will be accurately r eviewed, thus showing that such procedures are often cumbersome and inaccur ate. It is worth noting that for the first time, alpha (B) and alpha (S) wi ll be studied in detail.