Error Instability in Floating Gate Flash Memories Exposed to TID

Abstract

We discuss new experimental results on the post-radiation annealing of Floating Gate errors in Flash memories with both NAND and NOR architecture. We investigate the dependence of annealing on the program level, linking the reduction in the number of Floating Gate errors to the evolution of the threshold voltage of each single cell. To understand the underlying physics we also discuss how temperature affects the number of Floating Gate errors

Alpha-induced soft errors in Floating Gate flash memories

“…4. This is in agreement with the behavior reported after heavy-ion exposure [10] and also after TID irradiation [11]. For converse, the increase of intrinsic errors as time passes is negligible in a fresh, non-irradiated device, in the considered timeframe (Fig.…”

Ultra-Low Power Consuming Direct Radiation Sensors Based on Floating Gate Structures

“…Among them, Photoelectric effect and Compton scattering are relevant for C-Sensor operation, due to the energy range of particles in practical applications (from few keV to few MeV) and sensor material (Silicon). The charges, generated in the mentioned mechanisms, can discharge the C-Sensor FG by two possible scenari [28][29][30] (Figure 4):…”

“…Among them, Photoelectric effect and Compton scattering are relevant for C-Sensor operation, due to the energy range of particles in practical applications (from few keV to few MeV) and sensor material (Silicon). The charges, generated in the mentioned mechanisms, can discharge the C-Sensor FG by two possible scenari [28][29][30] (Figure 4 Since each of the two above mentioned mechanisms ("emission" and "separation") is associated with different part of C-Sensor-namely, Poly and STI-we investigated the contribution of each mechanism by modifying the cell design and studying the response to different types of radiation.…”

Increase in the Heavy-Ion Upset Cross Section of Floating Gate Cells Previously Exposed to TID

“…It is worth to note that all the post-radiation measurements throughout this work (after both TID and heavy-ion exposure) were performed several days after exposure, when most of the post-radiation annealing of FG errors was practically over (the tunnel oxide is only 10-nm thick in these devices). As a consequence, annealing phenomena [13], [14] are accounted for and the errors we detect in the cells can be mainly attributed to charge loss from the Floating Gate [11]. We recall that all the peripheral circuitry was shielded during all irradiations, so that any effect in the control building blocks can be ruled out.…”

“…This procedure was repeated on 10 FG memory sectors (each made of cells) to gain enough statistical accuracy (in the order of thousands of errors per experimental point). All the measurements have been performed several days after both TID and heavy-ion exposure, when the bulk of post-radiation annealing phenomena [13], [14] can be considered over.…”