LOW-LEVEL GATE CURRENT INJECTIONS IN FLASH MEMORIES INITIATED BY MINORITY-CARRIER COLLECTION ACTION OF FLOATING TERMINALS

An unintentional channel hot carrier injection phenomenon is reported for Flash Memory cells, The injection occurs near the source metallurg ical junction during electrical erase and is caused by subthreshold le akage current between source and boating drains, This mechanism is ini tiated by a minority carrier population (electrons) which is generated by impact ionization around the source junction and later collected b y the floating drains, Subsequently, when the floating gate potential approaches threshold voltage, these collected electrons drift from the drain toward the source, When they reach the source junction depletio n region, they experience carrier multiplications and some hot carrier s are injected onto the floating gate, The injected carriers can be ei ther hot holes or hot electrons depending on the magnitude of the floa ting gate potential, This mechanism affects the final threshold voltag e distribution of Flash Memories, especially when the electric field a cross the tunnel oxide is low.