Floating gate nonvolatile memory using individually cladded monodispersed quantum dots

Abstract

This paper presents nonvolatile memory characteristics of a quantum dot gate floating gate nonvolatile memory (QDNVM) that employs SiOx-cladded silicon quantum dots as discrete charge storage nodes of the floating gate. The cladding of Si quantum dots and control of their size are shown to result in a faster access and improved retention time. The floating gate is formed by site-specific self-assembly of SiOx-Si quantum dots on the tunnel oxide layer over the p-region between source and drain of an n-channel field-effect transistor (FET). Experimental data on fabricated long channel devices show threshold voltage shift as a function of duration and magnitude of the electrical stress applied during the “Write” operation. Current–voltage characteristics (ID–VD and ID–VG) are presented before and after stress. The electrical characteristics are explained using a quantum dot gate FET model which includes the threshold voltage shift (VTH) as a function of charge on the floating gate quantum dots due to applied electrical stress.