Multilevel Charge Storage in a Multiple Alloy Nanodot Memory

Abstract

A multilevel charge storage in a multiple FePt alloy nanodot memory is investigated for the first time. It is demonstrated that the memory structure with multiple FePt nanodot layers effectively realizes a multilevel state by the adjustment of gate voltage. Metal oxide semiconductor (MOS) capacitors with four FePt nanodot layers as a floating gate are fabricated to evaluate the multilevel cell characteristic and reliability. Here, the effect of memory window for a nanodot diameter is also investigated, and it is found that a smaller dot size gives a larger window. From the results showing good endurance and retention characteristics for the multilevel states, it is expected that a multiple FePt nanodot memory using Fowler–Nordheim (FN) tunneling can be a candidate structure for the future multilevel NAND flash memory.