Depassivation of Traps in the Polysilicon Channel of 3D NAND Flash Arrays: Impact on Cell High-Temperature Data Retention
Mattia Giulianini, Gerardo Malavena, Luca Chiavarone, Alessandro Sottocornola Spinelli, Christian Monzio Compagnoni · 2023
In this paper, we report clear experimental evidence proving that programmed cells in a 3D NAND Flash memory array may experience an unexpected average increase in their threshold voltage (VT) during high-temperature data retention. The phenomenon is explored as a function of the VTlevel of the monitored cells, the string back-pattern, and the data-retention temperature. A physical picture is then proposed to explain its origin, which is traced back to the depassivation of some traps in the polysilicon channel of the 3D NAND strings. Results point out a new reliability issue to address and tackle in the design of next generation 3D NAND Flash technologies.