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Flash memories operating in space are subject at the same time to the progressive accumulation of total ionizing dose and to intrinsic aging phenomena. In this work we investigate latent Total Ionizing Dose (TID) effects in 41-nm NAND single level cells that do not display neither floating gate errors nor any apparent kind of degradation after exposure. Retention of irradiated cells is analyzed at room and high temperature as a function of total dose previously received. We found that FG cell retention at room temperature is practically unchanged after a total dose up to 30 krad(Si). On the contrary, TID exposure slightly worsens the cell retention time during high-temperature tests. We attribute this behavior to the removal of compensating electrons from the tunnel oxide at high temperature

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This work investigates cycling-induced thresholdvoltage instabilities in nanoscale NAND Flash cells as a function of the array background pattern. Instabilities are mainly the result of charge detrapping from the cell tunnel oxide during post-cycling idle/bake periods and represent one of the major reliability issues for multi-level devices. Results reveal, first of all, that instabilities in a (victim) cell do not depend only on its memory state, but also on the memory state of its first neighboring (aggressor) cells. This new interference effect is shown to decrease in magnitude for higher threshold-voltage levels of the victim cell and to come mainly from an interaction with aggressor cells in the bit-line direction. From this evidence, a physical picture explaining the phenomenon and its main dependences is provided.

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