Single Event Effects in NAND Flash Memory Arrays

We are showing for the first time the charge loss due to heavy ion irradiation on Flash memory arrays organized following the NAND architecture. Results complement those previously found for devices featuring a NOR architecture: large charge loss can be expected after the hit of a single ion on a single memory cell. The resulting threshold voltage shift DeltaVTH grows with ion LET and with applied electric field across the tunnel oxide (that is, with the programming conditions) and cannot be explained by simple generation-recombination-transport models. Further, in Floating Gates hit by a single ion a percolation path develops across the tunnel oxide, able to slowly discharge the Floating Gate