Ferroelectric (Fe)-NAND Flash Memory With Batch Write Algorithm and Smart Data Store to the Nonvolatile Page Buffer for Data Center Application High-Speed and Highly Reliable Enterprise Solid-State Drives

A ferroelectric (Fe)-NAND flash memory with a batch write algorithm and a smart data store to the nonvolatile page buffer is proposed. An enterprise solid-state drive (SSD) for a data center is a future promising market of NAND flash memories. The critical problem for such an enterprise SSD is a slow random write. The write unit in a NAND flash memory is a page, 4-8 KBytes. Because the minimum write unit of the operating system is a sector, 512 Bytes, a random write to write a smaller data than a page size frequently happens, which creates a garbage. As a garbage accumulates, a garbage collection is performed to increase a workable memory capacity. The garbage collection takes as much as 100 ms, which is 100 times longer than a page program time, 800 μs, and thus causes a serious performance degradation. In the proposed Fe-NAND flash memory, the data fragmentation in a random write is removed by introducing a batch write algorithm where a page buffer in the Fe-NAND flash memory temporarily stores a program data. The memory cell program starts after the program data as much as the page size accumulates in page buffers. As the data fragmentation is eliminated, the SSD performance can double. In addition, the nonvolatile page buffer realizes a power-outage-immune highly reliable operation. With a low program/erase voltage of 6 V and a high endurance of 100 million cycles, the proposed Fe-NAND flash memory is most suitable for a highly reliable highspeed low-power data-center-application enterprise SSD.