Threshold voltage shift in FIB circuit edit of embedded flash device

This study presents FIB modification effect on pre-programmed Flash devices, sampled from 2 process technologies. No Vt shift is observed during FIB milling with or without the XeF₂ etching gas for enhanced milling process. But FIB-induced metal deposition causes significant amount of Vt shift. The maximum Vt shift of 400 mV in FIB-induced tungsten deposition is considerably smaller when compared to the maximum of 800 mV in platinum deposition. To minimize the effect of Vt shift during FIB circuit-edit, tungsten deposition should be used for FIB editing of interconnects as part of the Flash design debug process. For Pt deposition of a specific area size and thickness, varying the FIB ion currents do not significantly change the amount of Vt shift.