A 5 volt high density poly-poly erase flash EPROM cell

A 5-V-only flash EPROM (erasable programmable read-only memory) cell is described which is programmed by channel-hot-electron injection and erased through a poly-poly oxide. The cell consists of a self-aligned split-gate EPROM and a polysilicon erase line. A charge-pumping technique which takes advantage of very low programming current is used to ensure fast programming at a worst case condition of 125 degrees C and 4.5-V supply. An over-erase technique is used to achieve a uniform erase, high read current, and extended endurance. The flash cell is implemented in a staggered virtual ground-array which yields a cell size of 18 mu m with 1.2- mu m design rules in a double-poly CMOS EPROM process.<
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