A self-convergence erasing scheme for a simple stacked gate flash EEPROM

Abstract

A novel erasing method for simple stacked gate flash EEPROMs is described. The method makes use of avalanche hot carrier injection after erasure by Fowler-Nordheim tunneling. The threshold voltages converge to a certain 'steady-state' as a result of the injection. The steady-state is caused by a balance between avalanche hot electron injection into the floating gate and avalanche hot hole injection into the floating gate, and can be controlled easily by the channel doping. Tight distribution of threshold voltages and stable erasure without over-erased cells are demonstrated by applying cells using 0.6- mu m CMOS technology. In addition, short erase time is realized using the novel erase sequence.<>