Sample-to-Sample Variability and Bit Errors Induced by Total Dose in Advanced NAND Flash Memories

The variability in the total ionizing dose response of 25-nm single level cell NAND Flash memories from two different lots is studied. More than 1 Terabit of floating gate cells were irradiated with gamma rays and the number of errors was statistically analyzed. The behavior of the two lots is remarkably different in terms of floating gate errors. The statistical parameters such as mean, standard deviation, and shapes of the error distributions were studied. The sample-to-sample statistical distribution of TID errors is not Gaussian and it is attributed to variability in neutral cells, due to phenomena such as random discrete dopant fluctuations. Finally, the impact of scaling on variability is discussed