A Reliable Nonvolatile Memory Using Alloy Nanodot Layer with Extremely High Density

Abstract

A new nonvolatile memory with high density and high work-function metal nanodots, metal nanodot (MND) memory, was proposed and fundamental characteristics of MND capacitor were evaluated. In this work, a nanodot layer of FePt with high density and high work-function (∼5.2 eV) was fabricated as a charge storage site in nonvolatile memory, and its electrical characteristics were evaluated for the possibility of nonvolatile memory in view of cell operation by Fowler–Nordheim (FN) tunneling. Here, a nanodot FePt layer was controlled as a uniform single layer with dot size of under ∼2 nm and dot density of ∼1.2×1013/cm2. Electrical measurements of metal–oxide–semiconductor (MOS) structure with FePt nanodot layer shows a threshold voltage window of ∼6 V using FN programming and erasing, which is satisfactory for operation of the nonvolatile memory. Furthermore, this structure provides better data retention characteristics compared to other metal dot materials with similar dot density in our experiments. From these results, it is expected that this nonvolatile memory using an FePt nanodot layer with high dot density and high work-function can be a candidate structure for the future nonvolatile memory.