Nand Flash Memory Devices
S. Aritome · 2015
The most important requirement for NAND flash memory is a low bit cost. This chapter discusses the NAND flash memory cell and its scaling technologies. Requirements for isolation in NAND flash memory cell are more severe than other devices due to high-voltage operation during programming. Therefore, it was difficult to scale down of local oxidation of silicon (LOCOS) isolation width beyond 1.5-μm width due to boron diffusion from isolation bottom by LOCOS oxidation process. Then, a new field through implantation (FTI) process was developed. Next, the self-aligned shallow trench isolation cell (SA-STI cell) with floating gate (FG) wing had been developed. The chapter presents the planar FG cell and also discusses the side wall transfer-transistor (SWATT) cell as alternate memory cell technology for a multilevel NAND flash memory cell. Finally, it presents other advanced NAND flash device technologies.