Constrained Flash Memory Programming

Provided by: Israel Institute of Technology
Topic: Storage
Format: PDF
In NAND flash memory featuring Multi-Level Cells (MLC), the width of threshold voltage distributions about their nominal values affects the permissible number of levels and thus storage capacity. Unfortunately, inter-cell coupling causes a cell's charge to affect its neighbors' sensed threshold voltage, resulting in an apparent broadening of these distributions. The authors present a novel approach, whereby the data written to flash is constrained, e.g., by forbidding certain adjacent-cell level combinations, so as to limit the maximum voltage shift and thus narrow the distributions.

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