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

Abstract

A new erasing method for a simple stacked gate Flash EEPROMs is described. The method makes use of avalanche hot carrier injection after erasure by Fowler-Nordheimv-N) 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 the avalanche hot electron injection into the floating gate and the 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 0.6pm CMOS technology. In addition, short erase time is realized using the new erase sequence.

Flash memory cells-an overview

“…Besides the already mentioned method of iterating the erase algorithm, two self-convergent methods have been proposed, both relying on reprogramming techniques after erasure: hot-carrier injection (HCI) reprogramming [64] (i.e., ap- plying 5 V on drain and grounding word-lines for 0.5 s) or FN channel reprogramming [65] (i.e., applying 16 V at the word-lines). The erase scheme proposed in [64] uses channel-electron-induced avalanche HCI to bring the erase distribution to convergence after FN tunneling erase. This scheme does not require either programming all bytes before erasure by FN tunneling or iterating the erase/verify sequence.…”

Reliability issues of flash memory cells

“…A self-convergence erasing scheme, which is proposed by Yamada et al [36], can also be used to prevent overerasing. This method uses avalanche hot carrier injection after erasure by Fowler-Nordheim tunneling.…”

The effect of CHE and CHISEL programming operation on drain disturb in flash EEPROMs

“…Note that disturh under CHE operation is caused by heating and subsequent injection of electrons originating from S I D leakage [6]. However, the cell V, (during programming) is higher for CHISEL operation because of V, induced body shift, which results in reduced S I D leakage.…”