Plasma-induced in-line charging and damage in non-volatile memory devices

Abstract

Plasma-induced charging in oxide/nitride/oxide (ONO) inter-dielectrics and stress damage to tunnel oxides were extensively investigated on flash memory devices. Experimental data indicated that plasma-induced in-line charging in the ONO dielectric film and tunnel oxide damage were the two mechanisms responsible for UV threshold voltage fluctuation and transconductance degradation in non-volatile memories. The degree of plasma charging in ONO dielectric and tunnel oxide increases with increasing device antenna ratios. In this paper, a physical model was successfully developed and used in explaining the observed UV threshold voltage and transconductance dependencies on device antenna ratio and stress condition. A technique of utilizing a P/sup +/-diode structure to provide effective protection against plasma-induced ONO charging and tunnel oxide stress was also demonstrated on flash memories. >