SHF: Small: Approximate-Computing Enabled Robust 3D NAND Flash Memories

传统的 NAND 闪存已普遍用作几乎所有计算机系统的存储。通过技术扩展，可以增加 NAND 闪存容量，以满足当今不断增长的数据量的要求。然而，由于平面 NAND 单元的性能和可靠性下降，进一步的微缩化已经戛然而止。因此，3D NAND闪存设计为持续密度增加开辟了新方向，因为可以通过在垂直方向堆叠更多单元来倍增容量，而无需进一步缩小单元尺寸。尽管如此，3D NAND由于其新的架构也面临着可靠性方面的新挑战。使用强纠错机制受到潜在的高功耗、实施面积和长操作延迟的限制。另一方面，由于当今的许多应用程序都可以容忍少量错误，因此在计算和数据存储期间存在放宽数据准确性的趋势。该项目旨在利用这种近似数据存储来提高 3D NAND 闪存的可靠性、性能和耐用性。该研究将首先构建可靠性模型来指导架构设计。然后，将开发和评估通过容忍错误和近似编程来实现近似存储的机制。最后，将开发新技术来利用近似来减轻干扰、单元间干扰、保留损失，并提高 3D 闪存的性能和耐用性。该项目的成功将推动主流存储技术的不断扩展。它还将使3D NAND闪存在嵌入式系统、个人电脑和云中得到广泛采用，这将对存储行业的创新产生巨大的推动力。受过培训的学生将成为未来的工作组，继续计算领域的技术创新。

Traditional NAND flash has been prevalently used as the storage for essentially all computer systems. Increasing the NAND flash capacity, to meet the requirement of today's ever increasing data volumes, has been enabled by technology scaling. However, further scaling has come to a screeching halt due to degraded performance and reliability in planar NAND cells. 3D NAND flash memory design thus opens a new direction for continuous density increase, as capacity can be multiplied by stacking more cells in vertical direction without further shrinking the cell sizes. Nonetheless, 3D NAND also faces new challenges in reliability due to its new architecture. Using strong error correction mechanisms is limited by potential high power consumption, implementation area and long operation latency. On the other hand, there is a trend in relaxing data accuracy during computing and data stores as many of today's applications are tolerant to a small amount of errors. This project aims to leverage such approximate storage of data to improve the reliability, performance and endurance of 3D NAND flash memories. The research will first construct reliability models to guide architecture designs. Then, mechanisms for achieving approximate storage through tolerating errors and approximate programming will be developed and evaluated. Finally, new techniques will be developed to exploit approximation for mitigating disturbance, cell-to-cell interference, retention loss, and for improving performance as well as endurance of a 3D flash memory. The success of this project will fuel the continuous scaling of the mainstream storage technology. It will also enable pervasive adoption of 3D NAND flash memories for embedded systems, personal computers and clouds, which will have a tremendous drive for the innovations in storage industry. Trained students will become future taskforce to continue technology innovations in computing.