Poly-Si Channel-Induced Time Instability of 3D NAND Flash Cell Threshold-Voltage: A Comprehensive Temperature Analysis
D. G. Refaldi, G. Malavena, M. Burattini, D. Zerbini, L. Chiavarone, A. G. Mauri, A. S. Spinelli, C. Monzio Compagnoni · 2026
In this work, we investigate the time instability of the threshold voltage ($V_{T}$) of 3D nand Flash cells arising from the polycrystalline nature of their Si channel over an extremely wide temperature ($T$) range going from room temperature (RT) down to 4.2 K. Experimental data reveal that the magnitude of cell$V_{T}$instability, first, increases from RT down to about 150 K and, then, decreases below the latter$T$. Through TCAD simulations, this behavior is explained as the outcome of the change with$T$of the number of charge carriers trapped at the grain boundaries (GBs) involved in the phenomenon and of their impact on$V_{T}$. As a result of the observed turnaround, poly-Si channel-induced$V_{T}$instability does not trouble the reliability of 3D nand Flash cells in the cryogenic regime more than at RT.