On Enhancing Data Integrity with Low-cost Retention-Refillable Programming Scheme

Abstract

The retention error has become one of the most challenging reliability issues of flash memory due to the shrinking of the technology nodes. To enhance data integrity by resolving the retention error issues for 3D MLC flash memory devices (e.g., SSDs and SD cards), many excellent works that exploited in-place reprogramming and data refreshing concepts have been proposed in recent years. However, these approaches could result in additional issues, such as programming disturbance and performance overhead (e.g., unavoidable data refreshing and a larger amount of program and verify shots). This work is motivated by the need to explore a low-cost solution for resolving retention error issues without incurring negative impacts caused by conventional refresh-based and in-place reprogramming approaches. As a result, this work exploits the characteristics of the cell's Vt distribution and proposes the novel concept of "retention-refilling" to enhance data integrity. With such an idea, a retention-refillable programming scheme is proposed to improve flash reliability and mitigate performance overheads by trading data refreshing with retention-refilling. The capability of the proposed scheme is evaluated by a series of experiments, for which we have very encouraging results.