A Novel quasi-SLC(qSLC) Program/Erase Scheme in Ultra-Densified Charge-trapping 3D NAND Flash Memory to Enhance System Level Performance

In this work, a novel quasi SLC (qSLC) scheme is proposed and verified in TLC 3D NAND flash memory chip. Instead of the standard Program/Erase (P/E) scheme, qSLC performs sequential programming to overwrite the previously programmed data directly. Erase is activated only when the program states reach the highest levels. Since qSLC is a step-up programming scheme between adjacent double levels, the latencies can be well suppressed and the error bits can be largely reduced. In comparison with the standard TLC mode, using the qSLC scheme can obtaiñ90% error bits’ reduction and at least +75% total workload enhancement.