Impact of Source Junctions on the Performance and Cycling-Induced Degradation of Split-Gate Flash Memory

Abstract

The impacts of different source junctions on the program/erase speed and cycling degradation are studied in details for split-gate memory using source-junction-side FN erase and source-side injection program. The device with pure phosphorous source junction has faster program but slower erase speed than that with phosphorous plus arsenic source junction, mainly because of stronger coupling between floating gate and pure phosphorous junction. During program/erase cycling, the memory cell with phosphorous junction shows much higher program-VT rise but less erase-VT increase than that with phosphorous-plus-arsenic junction. For the phosphorous junction, it is found the cycling-induced damage is mainly caused by program operation near the injection point. For the phosphorous-plus-arsenic junction, however, program and erase generate almost equal amount of damage near the injection point and the source junction, respectively. Anneal after phosphorous-plus-arsenic implant improves cycling performance due to less abrupt junction.