Multilevel programming at a low-voltage step using junction avalanche hot carrier injections

Abstract

A highly efficient program method is proposed for multilevel programming with a low-voltage step in a conventional polycrystalline silicon-oxide-nitride-oxide-silicon structure. This method uses junction avalanche hot carriers for charge storage in the nitride layer. A multilevel storage is easily obtained by using a low-voltage step of 0.1 V at each level of the three programmed states along with a fast program time of 1 μs. In addition, a localized charge-injection near the junction edge is clearly observed with an acceptable read margin and threshold voltage difference between the forward and the reverse read at the three programmed states.