Effects of front-end-of line process variations and defects on retention failure of flash memory: Charge loss/gain mechanism

Retention fails on flash memory were comprehensively characterized and fault-isolated for the formulation of failure mechanism. Using in-depth TEM and SIMS characterizations based on electrical findings, we found that FEOL process variations such as contact misalignment (spacer encroachment) and defects (ONO instability and stacking fault), result in retention fail of flash memory. In this paper, the failure mechanism of retention fail governed by charge loss/gain in a same cell is explicated and knobs for robust reliability and decent production are proposed from design and process perspectives.