New buried channel FLASH memory cell with symmetrical source/drain structure for 64 Mbit or beyond

摘要

FLASH memory uses an injection of channel hot electrons for programming and FN tunneling for erasing. Therefore high supply voltages are required in order to generate and inject many hot electrons and to flow FN tunneling current at each operation mode. Moreover an asymmetrical source/drain structure has been widely used for increasing the electric field at the drain side and decreasing the field at the source side. These cause serious problems for scaling down in the future. To overcome these difficulties, a novel FLASH memory cell with symmetrical source/drain structure has been developed. Moreover, nitrogen is incorporated into floating gate by implantation to improve the tunnel oxide quality. Here, we report on the results of the characteristics of the novel FLASH memory cell.